Utility Services :

The utility services consist of many things. Any service or facility provided by an organization comes under it. Any activity which supports the main activity or process is an utility.

For example when you buy a house your main objective is shelter (i.e. you want to live there). Facilities like electricity, television, Internet, potable water supply or air-conditioning assist the main purpose. So all these are the utility services.

Consider an oil refinery the things that assist in operation but not take part in the main process are steam (for heating ), compressed air ( for pneumatic devices) along with basic things like electricity ,water supply ,waste disposal etc.

Types :

1. Public Utilities :This includes:a) Water supplyb) Drainagec) Storm waterd) Gas (cooking)e) Electricity /Communication

2. Industry SpecificThis includes:a) Steamb) Compressed airc) Nitrogen / Ammonia or other gasesd) Hot/Cold water

Codes and Standards used :

• ASME Code for Pressure Piping, B31

B31.1 Power Piping

B31.3 Process Piping

B31.9 Building Services Piping

• Other Standards

American Petroleum Institute

American Welding Society

American Water Works Association

Identifying utility lines:

a) In a Process and flow diagram : -Utility lines can be assigned letter U and then depending on various lines the number follows the corresponding letter.e.g. U123 indicates utility line with no.123. Or

- Depending on the type of fluid the lines can be further numbered. For example lines for process fluids can have numbering in one range, say, 1 to 100, utility lines can have numbering falling in another range, say, 101 to

200 and so on. -Also fluid to be handled can be mentioned. e.g. CHS may indicate chilled water supply, CHR may indicate chilled water return, DMS may indicate DM water supply ,STM to indicate steam.

Example: U154/STM/PRO-SEC/350 This nomenclature indicates Utility Line with Steam flowing through it. The line is located in the Process Section of the plant, of size 350 NB.

b) In Practice :It is marked by a utility marking tape with various colour codes

Certain guidelines :a) Utility marking tape shall be acid and alkali-resistant polyethylene film 6 inches wide with

minimum thickness of 0.004 inch.

b) Tape shall have a minimum strength of 1750 psi lengthwise and 1500 psi crosswise. c) The tape shall be manufactured with integral wires, foil backing, or other means to enable

detection by a metal detector when the tape is buried up to 3 feet deep. d) The tape shall be of a type specifically manufactured for marking and locating underground

utilities.e) Tape color shall be as specified in TABLES and shall bear a continuous printed inscription

(black lettering) describing the specific utility.

For Public Utilities :

For Industry :

Public Utilities :

a) Water supply:b) Drainage (Sewage):c) Storm water piping:d) Electricity / Communication / Gas :

4.a.) Water supply :

-To our homes and to the industries is mostly controlled and managed by a municipal body (BMC).-General Terminology:

(1) Water works. All construction (structures, pipe, equipment) required for thecollection, transportation, pumping, treatment, storage and distribution of water.

(2) Supply works. Dams, impounding reservoirs, intake structures, pumping stations,wells and all other construction required for the development of a water supply source.

(3) Supply line. The pipeline from the supply source to the treatment works ordistribution system.

(4) Distribution system. A system of pipes and appurtenances by which water isprovided for domestic and industrial use and fire fighting.

(5) Distribution mains. The pipelines that constitute the distribution system.

(6) Service line. The pipeline extending from the distribution main to building served.

-Water Supply Network :

> Lake/Pond/River> Water purification> Storage> Pumping> Pipe Network (we are concerned with this only in piping)> Connection to sewers.

Pipe network in water supply :

Design considerations

Pipe materials

Design :

Size water lines by using the Darcy - Weisbach formula by extracting data from Moody diagrams for friction losses in pipe. ( Water piping systems use pressure (conveying water at a pressure above atmospheric) to allow the fluid to flow for long runs and uphill. Pressure systems use pumps to create that pressure. For example, a public water supply system may have a pump at elevation 100.00 that pumps to an 80 psi pressure. Assume the piping system will lose 1 psi pressure for every 3000 feet of pipe. A house that is 6000 feet from the pump and at elevation 90.00 will lose 2 psi from gravity losses and gain 5 psi from elevation change (pressure changes about 1/2 psi for every one foot of elevation change), so the water pressure at that house is 83 psi. Another house 18,000 feet from the pump at an elevation of 140.00 will lose 6 psi from friction losses and 20 psi from elevation change. The water pressure at that house will be 54 psi. This example illustrate the effect of friction losses and elevation changes on pressure piping)

Design water mains to maintain a normal operating pressure range of 40 to 100 psi in distribution mains and building service lines.

Loop- grid type of system providing two-way flow with sectional valves arranged to provide alternate flow paths to any point in the system. (any Section fails it can be isolated and connection to other system is not affected)

Where service lines enter the building provide suitable flexibility to protect against differential settlement or seismic activity.

Locate portable lines in a separate trench from sewer lines. Where feasible, portable lines shall not be routed within 10 feet of sewer lines.

Where portable mains must cross sewers, it shall pass 2 feet above the sewer lines. Accessories required:

a) Provide accessible shut-off valves at branches serving floors or multiple fixture arrangement

b) The meter stop is a ground-joint valve, which controls and shuts off the flow of water into the building. Place the meter stop as close to the service pipe entry as possible.

c) The water meter, installed near the meter stop, measures the amount of water used in the building.

d) Install reduced pressure type backflow preventer at branch lines supplying process water. Locate it within 5 feet of floor level.

e) Pressure relief and surge relief valves to take care of water hammer effect.f) Install air release and vacuum valves at high points in long supply lines.

Example of underground plan :

Pipe materials :

1. Galvanized steel( 3/8’’ to 2’’) :-Durable but when galvanized zinc coating has degraded there is rusting-Life is about 30-50 years-It is not used for new connections.

2. Copper :

Common wall-thicknesses of copper tubing are "Type K", "Type L" and "Type M":[2]

Type K has the thickest wall section of the three types of pressure rated tubing and is commonly used for deep underground burial such as under sidewalks and streets, with a suitable corrosion protection coating or continuous polyethylene sleeve as required by code.

Type L has a thinner pipe wall section, and is used in residential and commercial water supply and pressure applications.

Type M has the thinnest wall section, and is generally suitable for condensate and other drains,.

Disadvantages :-Susceptible to cold water pitting. (contamination)-Erosion corrosion (high speed /turbulence)-Pin holes due to stray current. Pin-hole leaks can occur anytime copper piping is improperly grounded and/or bonded; nonmetal piping, such as Pex or PVC, does not suffer from this problem. The phenomenon is known technically as stray current corrosion or electrolytic pitting.

Nominalsize

Outside diameter(OD)

[in (mm)]

Inside diameter (ID)[in (mm)]

Type K Type L Type M

3⁄8 1⁄2 (12.7) 0.402 (10.211) 0.430 (10.922) 0.450 (11.430)

1⁄2 5⁄8 (15.875) 0.528 (13.411) 0.545 (13.843) 0.569 (14.453)

5⁄8 3⁄4 (19.05) 0.652 (16.561) 0.668 (16.967) 0.690 (17.526)

3⁄4 7⁄8 (22.225) 0.745 (18.923) 0.785 (19.939) 0.811 (20.599)

1 11⁄8 (28.575) 0.995 (25.273) 1.025 (26.035) 1.055 (26.797)

11⁄4 13⁄8 (34.925) 1.245 (31.623) 1.265 (32.131) 1.291 (32.791)

11⁄2 15⁄8 (41.275) 1.481 (37.617) 1.505 (38.227) 1.527 (38.786)

2 21⁄8 (53.975) 1.959 (49.759) 1.985 (50.419) 2.009 (51.029)

21⁄2 25⁄8 (66.675) 2.435 (61.849) 2.465 (62.611) 2.495 (63.373)

3 31⁄8 (79.375) 2.907 (73.838) 2.945 (74.803) 2.981 (75.717)

3. Plastics :

Plastic pipe is in wide use for domestic water supply and drainage, waste, and vent (DWV) pipe. For example, polyvinyl chloride (PVC), chlorinated polyvinyl chloride(CPVC), polypropylene (PP), polybutylene (PB), and polyethylene (PE) may be allowed by code for certain uses. Some examples of plastics in water supply systems are:

PVC /CPVC - rigid plastic pipes similar to PVC drain pipes but with thicker walls to deal with municipal water pressure, introduced around 1970. PVC should be used for cold water only, or venting. CPVC can be used for hot and cold potable water supply. Connections are made with primers and solvent cements as required by code.

PP - The material is used primarily in housewares, food packaging, and clinical equipment,[5] but since the early 1970s has seen increasing use worldwide for both domestic hot and cold water. PP pipes are heat fused, preventing the use of glues, solvents, or mechanical fittings. PP pipe is often used in green building projects.[6][7]

PBT - flexible (usually gray or black) plastic pipe which is attached to barbed fittings and secured in place with a copper crimp ring. The primary manufacturer of PBT tubing and fittings was driven into bankruptcy by a class-action lawsuit over failures of this system. However, PB and PBT tubing has returned to the market and codes, typically first for 'exposed locations' such as risers.

PEX - cross linked polyethylene system with mechanically joined fittings employing barbs and crimped steel or copper fittings.

4.b) Drainage (sewage):

Sanitary sewers require minimum exfiltration (sewage leaking out of the system and into the ground) and infiltration (groundwater leaking into the system). The main elements are pipe, manholes and clean-outs. The purpose of sanitary manholes is to allow inspection and cleaning of sewers and to remove obstruction. The minimum manhole diameter is typically four feet with 21" frame opening for access.

>Types of system:

A) Gravity System:

Most commonly used where topography is suitable for its installation.

B) Alternative System:

-There may be areas in which the topography is not well suited for construction of a gravity sewer system. In such areas, the installation of a gravity system would require deep and expensive trench excavation, jacking, boring, tunneling, or construction of long sewer lines to avoid unfavorable terrain

-Also depths of gravity sewers greater than 15 to 20 feet are usually uneconomical.

a) Wastewater pumping. -The operation and maintenance costs of a pumping station with a Forcemain, when capitalized, may offset or exceed the construction costs of a deep gravity sewer system. -Generally, a gravity sewer system will be justified until its cost exceeds the cost of a pumped system by 10 percent.

b)Low Pressure Systems. -Some areas under consideration may be further limited by high groundwater, unstable soil, shallow rock, or extremely adverse topography, and neither gravity sewers nor pump or ejector stations will be suitable. -To overcome these difficulties, low pressure systems using grinder pumps with small diameter (less than 100 mm (4-inch)) pressure sewers may be utilized. Low pressure systems are also used with flat topography where low flows are anticipated. -In a typical installation, wastewater from individual buildings will be discharged to a holding tank, and then periodically transferred by a grinder pump station through small diameter pipe, into either a central pressure main, conventional gravity sewer, pumping station, or wastewater treatment facility.

GRAVITY SEWER DESIGN:

-The Manning formula will be used for design of gravity flowsewers as follows:

where:C = 1 for SI units (1.486 for IP units)V = velocity in meters per second (feet per second)n = coefficient of pipe roughnessR = hydraulic radius in meters (feet), andS = slope of energy line in meters per meter (feet per foot)

(1) Roughness coefficient. Values of n to be used in the formula range from 0.013to 0.015.

(2) Velocity. Sewers will be designed to provide a minimum velocity of 0.60 meters persecond (2.0 feet per second) at the average daily flow, or average hourly flowrate, and aminimum velocity of 0.75 to 1.05 m/s (2.5 to 3.5 fps) at the peak diurnal flowrate(When velocities drop below 0.30 m/s (1.0 fps) during periods of low flow,organic solids suspended in the wastewater can be expected to settle out in the sewer.Sufficient velocity (0.75 to 1.05 m/s (2.5 to 3.5 fps)) must be developed regularly, once or twicedaily as a minimum, to resuspend and flush out solids which may have been deposited duringlow flows. A velocity of 0.75 m/s (2.5 fps) minimum is required to keep grit and sand suspended.However, new sewers which are properly designed and constructed should contain only minorquantities of grit or sand. Maximum velocity is set at 3.00 m/s (10.0 fps) in the event that gritbecomes a problem.)

(3) Slope. Assuming uniform flow, the value of S in the Manning formula is equivalent tothe sewer invert slope. Pipe slopes must be sufficient to provide the required minimum velocitiesand depths of cover on the pipe. Although it is desirable to install large trunk and interceptorsewers on flat slopes to reduce excavation and construction costs, the resulting low velocitiesmay deposit objectionable solids in the pipe creating a buildup of hydrogen sulfide, and thus willbe avoided.

General considerations in design:

- Generally, it is not desirable to design sewers for full flow, even atpeak rates. Flows above 90 to 95 percent of full depth are considered unstable, and may resultin a sudden loss of carrying capacity with surcharging at manholes.

-In addition, large trunk andinterceptor sewers laid on flat slopes are less subject to wide fluctuations in flow, and if designed to flow full may lack sufficient air space above the liquid to assure proper ventilation.

-Adequate sewer ventilation is a desirable method of preventing the accumulation of explosive, corrosive or odorous gases, and of reducing the generation of hydrogen sulfide.

-Therefore, trunk and interceptor sewers will be designed to flow at depths not exceeding 90 percent of full depth;laterals and main sewers, 80 percent; and building connections, 70 percent.

-However, regardless of flow and depth the minimum sizes to be used are 150 millimeter (6-inch) for building connections and 200 millimeter (8-inch) for all other sewers.

-BUILDING CONNECTIONS:Building connections will be planned to eliminate as many bends as practical. Bends greater than 45 degrees made with one fitting should be avoided; combinations of elbows such as 45-45 or 30-60 degrees should be used .

-In most situations where small to medium sized gravity sewers are installed in long runs, it will be safe to assume uniform flow throughout the entire length of conduit. However, in cases where larger sewers, 600-millimeter (24-inch) diameter and above,are constructed in runs of less than 30 meters (100 feet) ( it may contain number of control sections where nonuniform flow may occur)

Pipe Materials :

1.Ductile iron. -Ductile iron (D.I.) pipe is suitable for sewers and force mains used atpumping stations and wastewater treatment facilities. -D.I. pipe is susceptible to corrosion from acid wastes and aggressive soils. Cement, polyurethane,bituminous, or polyethylene linings are usually provided for interior protection. -However cement is not adequate for highly aggressive acid atmospheres; in such environments, pure fused calcium aluminate with pure fused calcium aluminate aggregates is recommended

2. Steel. -Galvanized steel pipe will only be used for small diameter mains and pressure sewers from 32 mm (1-1/4-inch) to 100 mm (4-inch) in size.

3. Cast iron. -Cast iron soil (C.I.S.) pipe will normally be allowed only as an option for buildingconnections. C.I.S. pipe is used primarily for building interior drainage, waste, and vent piping,-C.I.S. pipe is resistant to internal and external corrosion when provided with a bituminous coating, and is not subject to abrasion from grit, sand, or gravel. -C.I.S. pipe is available in 50 mm (2-inch) through 380 mm (15-inch) diameters, in 1.5 m(5-foot) and 3 m (10 foot) laying lengths, and is manufactured in service (SV) and extra heavy(XH) classifications.

4. Concrete-Concrete pressure pipe and sewer pipe is appropriate for applications requiringlarge diameter or high strengths. -A disadvantage is the lack of corrosion resistance to acids,

especially critical where hydrogen sulfide is generated in substantial quantities. However, special PVC or clay liner plates, coatings of coal-tar, coal-tar epoxy, vinyl, or epoxy mortar can be applied to the pipe for corrosion protection.-Non-reinforced concrete sewer pipe is generally available in diameters 100 mm(4-inch) through 750 mm (30-inch), and in minimum laying lengths of 1 m (3 feet). -Reinforced concrete (R.C.) pressure pipe in diameters 600 mm (24-inch) through3,600 mm (144-inch). -Reinforced concrete pipe will be used where high external loadings are anticipated, and large diameters or tight joints are required. -The advantages of R.C. sewer pipe include a wide range of diameters,(300 mm (12-inch) through 2,700 mm (108-inch), and laying lengths, 1.2 meters (4 feet) to 7.3 meters (24 feet), which are available)

5. PVC- PVC pipe is suitable for gravity sewers.

-It is chemically inert to most acidic and alkaline wastes, and is totally resistant to biological attack. Since it is a nonconductor,PVC pipe is immune to nearly all types of underground corrosion caused by galvanic or electrochemical reactions, in addition to aggressive soils.

-Durability, light weight, a high strength-to-weight ratio, long laying lengths, watertight joints and smooth interior surfaces are characteristics which make PVC pipe an attractive alternative for use in sewer systems.

- PVC sewer pipe is available in diameters 100 mm (4-inch) through 1,200 mm(48-inch), and in laying lengths of 3 to 6 meters (10 to 20 feet).

-Disadvantages include possible chemical instability due to long-term exposure to sunlight,excessive pipe deflection under trench loadings when installed improperly or subjected to hightemperature wastes, and brittleness when exposed to very cold temperatures.

3. Stormwater system :

Most storm sewer piping flows by gravity, no pumps create pressure. The storm water drops into the system by inlets or roof drains then flows downhill. Obviously, the grade of the pipe matters. A low spot, or belly, in the pipe makes a trap, while a high spot, or hump, creates a dam. So the pipe crew needs to keep the pipe inverts (the lowest spot in the pipe where the water flows) installed in a straight line, at the slope required on the drawings.

Some of the common issues that occur with storm sewer piping are:

1. Unexpected rock excavation

2. Existing pipes in the way, discovered only during the installation

3. Design errors that only become apparent during the installation

Most project I see these days use High Density Polyethylene (HDPE) pipe.

The Sometimes concrete pipe still comes through as the best choice, due to it's strength and durability.

Corrugated metal pipe (CMP) also gets used often

The degree to which storm sewer pipe must be water-tight is normally made clear in the project specifications. Sometimes, a bit of water leakage from storm sewer piping is acceptable (often a trade off for lower cost and easier installation) and other times the storm sewer piping must be water-tight under a low pressure.

Industry specific utility :

1. Compressed air2. Steam 3. Nitrogen

4. Ammonia

1.Compressed Air :

-Compressed air uses falls under the 3 categories

a) Power : In this application compressed air moves something or exerts a force. E.g. Pneumatic tool operations, Air lifts or cylinders.

b) Process: Compressed air used in this application becomes apart of the process itself. An example is the use of compressed airin a combustion process.

c) Control Purpose. Extensive use is made of compressed air to governand/or regulate various equipment by monitoring pressure or flowrates of some substance. A pneumatically controlled combustionsystem is an example of such an application.

TYPES OF AIR DISTRIBUTION SYSTEMS. -Compressed air is delivered by either aboveground or underground piping systems. -In many instances, however, life cycle economics have found that small air compressorsat the source are more feasible than a compressed air distribution system.

SELECTION OF ABOVEGROUND OR UNDERGROUND DISTRIBUTION SYSTEMS. :-The decision whether to use aboveground or underground piping shall be based on the lifecycle economics. The advantages of each system are as follows:

-Other Factors. The following considerations may have an importantinfluence on the final decision of which system to employ: Permanent versus temporary use Degree of hazard (for example, the potential danger that overheadpiping may cause to aircraft operations) Annual ownership, operation, and maintenance costs.

Design Considerations :

1.)Above-ground system :

(a) Spans. The maximum spans between pipe supports for straight piperuns depend on pipe size. Maximum spans for steel pipe and rigid coppertubing are shown

(b) Elevation Clearance. For distribution outside buildings, aboveground overhead lines may be located as little as 12 inches or as much as 22 feet above grade. The clearance above roadways is from 14 to 16 feet for automobile and truck traffic. For railroad crossings, the clearance is22 feet above grade. The minimum height for installations at low elevationsshould be sufficient to clear surface water.

(c) Pitch of Aboveground Lines. Air lines are pitched down a minimum of3 inches per 100 feet of length, in the direction of airflow, to low pointswhere the condensate is collected.

(d) Drip Legs. The low line points are provided with drip legs equippedwith scale pockets and automatic drain traps. When accessible, scale pocketsmay have a manual drain valve instead of an automatic drain trap. Drip legsare located at:

Low points

Bottom of all risers

Every 200 to 300 feet for horizontally pitched pipe

(e) Counter flow of Condensate. Where pipes must be sloped upward, causing condensate to run in a direction opposite to airflow, the pitch of the pipe is increased to a minimum of 6 inches per 100 feet.

2.)Underground distribution system:

(a) Pitch of Underground Systems. Air lines are generally pitched down a minimum of 3 inches per 100 feet of length, in the direction of airflow, to provide easy drainage of condensate.

(b) Drip Legs. In horizontally pitched buried pipes where traps are inaccessible, drip legs are located atintervals of not over 500 feet.

(c) Counter flow of Condensate.Where pipes must be sloped upward, causing condensate to run in a direction opposite to airflow, the pitch of the pipe is increased to a minimum of 6 inches per 100 feet.

General Considerations for both systems:

>When practical, pipelines distributing compressed air tonumerous branches or service outlets in a large area should form a closedloop. This maintains maximum pressure at branches and outlets and providestwo-way distribution to consumers.

>The use of a closed loop equipped with conveniently located segregating valves permits a partial shutdown of the system for inspection or repairs.

>Generally, provisions are made for bleeding each part of a loop between segregating valves.

>The loop pipe should be of sufficient size to prevent an excessive pressure drop at any outlet regardless of the direction of airflow around the loop.

>Branches shall be at the top of the main to prevent carryover of condensate and foreign matter.

Piping Material:

>Low-Pressure and Medium-Pressure Systems. (less than 250 psi ):

o Black steel pipe in appropriate thicknesses conforming to pipe Schedule 40, ASTM A 53 or A 120 is used in these systems and is joined preferably by welding.

o For special conditions, stainless steel pipe and copper tubing with appropriate fittings are also used.

> High-Pressure Systems:

o Seamless steel pipe conforming to ASTM A 53 or A 120, with Schedule determined in accordance with ANSI/API 510-1983, is commonly used for high-pressure air systems.

o When economic considerations dictate its use, small systems may employ stainless steel pipe with special fittings to assure a continuous supply of high quality air.

2.Steam :

• Not only is steam an excellent carrier of heat, it is also sterile, and thus popular for process use in the food, pharmaceutical and health industries. It is also widely used in hospitals for sterilisation purposes.

• The industries within which steam is used range from huge oil and petrochemical plants to small local laundries. Further uses include the production of paper, textiles, brewing, food production, curing rubber, and heating and humidification of buildings.

• Many users find it convenient to use steam as the same working fluid for both space heating and for process applications. For example, in the brewing industry, steam is used in a variety of ways during different stages of the process, from direct injection to coil heating.

Definitions and Terminology:

Trunk line distribution system. Distribution system with a large-diameter line leavingthe boiler plant; as lateral branches are installed off it for service, the trunkline gradually diminishes in diameter.

Main and feeder network distribution system. Distribution system that receives itssupply of steam through a high-pressure feeder main leading from the plant throughthe network; the size of the feeder main required in this case is not as large as ina trunk-line system with the same boiler-plant steam pressure.

Steam distribution systems:

(1) a trunk-line distribution network system :In this, the diameter of the trunk line leaving the boiler plant is large, andas lateral branches are installed off it for service, the diameter of the trunk line is

gradually reduced as the needs for carrying capacity are diminished.

(2) a main and feeder distribution network system.:In this, the main and feeder network distribution system receives its supplyof steam through a high-pressure feeder main leading from the plant through thenetwork. Advantage is taken of the pressure drop available for the transportation of large volumes of steam to the low-pressure network.

Design

The factors which determine the size of a steam pipe for a specificinstallation are as follows: (1) the initial steam pressure, and other conditions(temperature), (2) the minimum permissible discharge pressure, (3) the allowable velocity, (4) the quantity of steam, and (5) the length of line, including equivalent lengths for fittings.

The Unwin formula has been widely used in the district-heating industry formany years. At elevated velocities, Unwin’s formula gives pressure drops knownto be higher than actual. This formula, in English units, is as follows:

where ,P _ pressure drop (psi)W _ steam flow rate (lb/min)L _ length of pipe (ft)d _ pipe inside diameter (in)Y _ steam density (lb/ft3){ 0.3318 lb/ft3}

Velocity Table :

Design Considerations

-To prevent a water slug type of water hammer and apossible rupture of the steam main, condensed steam or condensate within thesteam main must be removed.

-The points to be drained are the low points in the line, moistureseparators, drip pockets, and valves, especially in vertical lines. -Horizontal portions of the steam lines should be pitched downward approximately 1⁄₈ in/ft (10 mm/m)in the direction of flow or 1⁄₄ in/ft (20 mm/m) for lines that contain a steam/watermixture or require draining periodically. -Condensate flow against the steam should be avoided if possible.-In any event, recommended lengths of steam main for drainingoff condensate should not exceed 300 to 400 ft (90 to 120 m).-To provide for condensate drainage from a steam main, a drain pocket iswelded to the bottom of the pipe to be drained. The diameter of the pocketshould be about one-third the diameter of the line, up to a maximum of NPS 6(DN150) forNPS18 (DN450) and larger mains. The pocket not only provides forcondensate removal but also allows for sediment removal.

Fig :Drain pocket for steam-trap connection to low-velocity steam main.

Pipe Materials :-Up to 775_F (413_C)—Carbon steel.

-Up to 950_F (510_C)—Use 11⁄₄ Cr. steelFrom more than 950 to 1050_F (510 to 566_C)—Use 21⁄₄ Cr. steelFrom 1000 to 1200_F (540 to 650_C)—Consider using 9–12 Cr steel

-From 1050 to 1200_F (566 to 650_C)—Consider using austenitic stainless steel.

-Beyond 1200_F (650_C)—Use austenitic stainless steel.

Utility Layout:

Utility Stations:• Provide and locate utility stations with water, steam, or air as indicated below:

All areas should be reachable with a single 50 foot (20m) length of hose from the station. Provide water outlets at grade level only, in pump areas, and near equipment that should be water washed during maintenance.

•Provide steam outlets at grade level only in areas subject to product spills, and near equipment that requires steaming out during maintenance.

•Provide air outlets in areas where air-driven tools are used such as at exchangers, both ends of heaters, compressor area, top platform of reactors, and on columns at each manway.

• Utility stations shall be provided as required for air, water, steam/hot water and nitrogen. Eachstation shall be numbered and located in the general working areas at deck level.

• Freshwater,seawater and plant air systems shall be equipped with hosereels. • Nitrogen stations shall not be located inside enclosed areas. Nitrogen hoses shall be

installed if required. (Different types of couplings shall be used for air and nitrogen.

Utility Layout :• The utility area should be near the process area. • The utility area should be arranged for easy access and adequate working area provided

around all equipment, for maintenance. • The cooling tower should be located to provide the least possible restriction to the free

flow of air, and away from areas where drift or fogging might create a problem. • The circulating fuel oil system that supplies oil for process heaters and boilers is usually

located in one corner of the utility area including tanks and circulating pumps. • All boilers are grouped together with space provided for at least one future boiler. All

boiler auxiliaries including de-aerator, feed pumps, flash drums and chemical feed systems are located in close proximity to the boiler. Consideration must be given to single stacks for each boiler or one common stack.

• Plant and instrument air compressors including dryers should be located in the utility area.

• Switchgear for the electrical system is placed in an enclosed building and located within the utility area. Substation serving process Units and offsite facilities are usually located in OGP process areas dependent upon the areas served.

• Utility control house shall be provided to house all board mounted instruments used for operation and control of utility equipment.

• Raw water storage and fire pumps shall be located adjacent to either the boilers or the cooling towers whichever provides the more economic arrangement.

• Critical steam and power facilities feeding major portions of the plant shall be protected from possible fire or explosion in equipment handling hydrocarbons.

• WASTE TREATMENT FACILITIES 1 The preferred location of the waste treatment area should be at a refinery/plant low point to insure gravity flow from all areas. Where this is not possible lift stations must be provided as required. 2 The waste treatment area should be remote from the process and utility area and arranged to permit future expansion of the system.

3 Layout of the area must include vehicle accessibility for maintenance purposes.

References :

• Pipingguide.net

• Piping Handbook (7th edition)

• Process Plant Layout (Roger Hunt)

• Engineering Handbook For Layout

• Maintenance of compressed air and steam system.( Navy handbook)

• Utility System for c41 (USA)

• Wikipedia

• Urban Design Standards Manual

• Waste Water Collection (USA)

• Certificate course on piping engineering (T.N. Gopinath)

Public utilities:1. Stormwater

Most storm sewer piping flows by gravity, no pumps create pressure. The storm water drops into the system by inlets or roof drains then flows downhill. Obviously, the grade of the pipe matters. A low spot, or belly, in the pipe makes a trap, while a high spot, or hump, creates a dam. So the pipe crew needs to keep the pipe inverts (the lowest spot in the pipe where the water flows) installed in a straight line, at the slope required on the drawings.

Some of the common issues that occur with storm sewer piping are:

4. Unexpected rock excavation

5. Existing pipes in the way, discovered only during the installation

6. Design errors that only become apparent during the installation

 Most project I see these days use High Density Polyethylene (HDPE) pipe. The are lots of variations of HDPE available, which are shown on the following

site:http://www.hancor.com/product/pipe.html

Sometimes concrete pipe still comes through as the best choice, due to it's strength and durability. Some concrete pipe options are shown on the following

site: http://www.shermandixie.com/products/pipe/index.php

Corrugated metal pipe (CMP) also gets used often and some CMP options are shown on the following

site: http://www.contech-cpi.com/drainage/products_materials/metal/corrugated_metal_pipe/144

The degree to which storm sewer pipe must be water-tight is normally made clear in the project specifications. Sometimes, a bit of water leakage from storm sewer

piping is acceptable (often a trade off for lower cost and easier installation) and other times the storm sewer piping must be water-tight under a low pressure.

2. Sewage Sanitary sewers require minimum exfiltration (sewage leaking out of the system and into the ground) and infiltration (groundwater leaking into the system). The

main elements are pipe, manholes and clean-outs. The purpose of sanitary manholes is to allow inspection and cleaning of sewers and to remove obstruction. The

minimum manhole diameter is typically four feet with 21" frame opening for access. Manholes are constructed of brick, block, poured-in-place concrete or precast

concrete. Special care must be taken to limit sub-grade settlement to avoid cracking the adjacent pipes. Solid, rather than grated, covers are used on sanitary

manholes to control odors. Ladder rungs must be securely anchored into the manhole walls and care taken that the steps will not pull out (fail) in several years.

Failure of a manhole ladder rung is a serious, and all too common, liability and it's avoidable. Clean-outs are used on smaller pipe and allow a location to insert

cleaning tools to flush the pipe.

The most common pipe used in sanitary sewer systems is PVC sewer pipe SDR-35, a typical manufacturer's website

is: http://www.dpcpipe.com/pdfs/SewerPipeSpecSheet.pdf

Sometimes concrete pipe still comes through as the best choice, due to it's strength and durability. Some concrete pipe options are shown on the following

site: http://www.shermandixie.com/products/pipe/index.php

Most sanitary sewer lines flow by gravity, which probably is the origin of the saying that shit flows downhill. The following US Dept of Defense guide for

designing gravity sewer piping helps you understand how to size pipes for different flows and slope conditions. I apologize for the lack of clarity for the

Manning Formula Nomograph Chart (the detail needs print quality not web monitor quality), but you can go to the Wastewater Collection Manual 

Entire pdf available –so ur good

For industry ,chemical sewers and their design (plant layout and undergroung chem. Sewers pdf)

Industry specific:Utility headersUtility headers for water, steam, air, etc. shall be arranged on the top of multi-tiered pipe racks.

Utilities Piping- Condensate- Instrument Air- Nitrogen- Plant Water- Plant Air- Potable Water- Steam- Glycol- Ammonia- Cooling Water- Chilled Water- Tracing Fluids (Low Temp. or High Temp.)

4.9.1 Air pipingAir piping shall have self draining provision at all low points for the collection of condensate. Airtraps shall be provided with isolation valves, balance lines and drains to local collection points.Instrument air headers and manifolds shall not be dead ended but supplied with blind flanges forcleaning and maintenance.All branches and take-offs shall be from the top of the headers.COMPRESSED AIR USES. Compressed air is a form of power which is very

useful in both miadvantage in applfrom its source,work intervals.service, processPowerlitary and industrial applications. “It isications that require intermittent power aas the air pressure can be maintained nearCompressed air uses fall into one of threeservice, or control purposes.of particularsome distancey constant duringcategories: powerService. In this application compressed asomething or exerts a force. Examples of power service uses arer either movespneumatic tool operation, air lifts, clamps, and cylinders.Process Service. Compressed air used in this application becomes apart of the process itself. An example is the use of compressed airin a combustion process. Compressed air provides oxygen for thecombustion process, and in turn it becomes a part of the combustionproducts and is no longer identifiable as air.Control Purpose. Extensive use is made of compressed air to governand/or regulate various equipment by monitoring pressure or flowrates of some substance. A pneumatically controlled combustionsystem is an example of such an application.2 COMPRESSED AIR DISTRIBUTION SYSTEM. Compressed airconsist of the following equipment:Piping required to transport the compressedcompressor plant to the consumersEquipment, instrumentation, and related fat’accomplish the above described purpose safelydistribution systemsair from a centrallit es required toand efficiently3 SUPPLY PRESSURE. Compressed air is distributed at low,pressures. It must be dry and free of oil, dust. or othermedium, or highcontaminants.Refer to NAVFAC MO-206, Operation and Maintenance of Air Compressor Plants,for methods of producing compressed air and removing moisture, oil, dust, andother contaminants.3.1 Low-Pressure Compressed Air Systems. These systems provide compressedair at pressures up to 125 psig. When several air pressures are requiredwithin that range, the plant is usually designed for the highest pressure,pressure reducing stations supplying the lower pressures as required. Typicallow-pressure applications follow.5-1

Application Pressure (psig)Air motors, crane drives, and 70- 125starting motors for, internalcombustion enginesShops 80- 100Laundries and dry cleaning 75 - 100plantsStarting aircraft jet engines 1 85Instrumentation and control 15- 50General service (tools, cleaning, 40 - 90painting)Sootblowing for HTW generators 100- 120and steam boilers1Medium-pressure compressed air may also be used for this purpose.3.2 Medium-Pressure Compressed Air Systems. These systems provide compressedair within the range of 126 to 399 psig. Such systems are not extensive andare generally provided with individual compressors located near the load.Typical applications for medium-pressure applications follow.Application Pressure (psiq)Starting diesel engines 100 - 399Hydraulic lifts 145 - 175Retread tire molds 175 - 2003.3 High-Pressure Compressed Air Systems. These systems provide compressedair within the range of 400 to 6,000 psig. To minimize the hazards that existwith higher pressures and capacities, separate compressors are used for eachrequired pressure. However, for systems at 3,000 psig that also requirerelatively small amounts of air at a lower pressure, but above 400 psig, airmay be supplied in the higher value for the main system and reduced to thelower pressure for small branches provided that safety relief valves areused. Examples of high-pressure applications follow.ApplicationTorpedo workshopPressure (psiq)600 and 3,000Ammunition depot 100, 750, 1,500 and 4,500Catapults 1,500Mind tunnel 3,000Testing laboratories 6,0004 AIR RECEIVERS. Air receivers are tanks installed in the compressor plantthat serve as reservoirs for the storage of compressed air. Air receiverspermit meeting peak demands in excess of compressor capacity and act aspulsation dampeners on reciprocating compressor installations. They alsoseparate, collect, and drain moisture, oil, and dirt from the system air.Figure 5-1 shows a typical air receiver.4.1 Secondary Air Receivers. Long distribution lines that are marginallysized may occasionally require secondary receivers located near a point ofheavy demand. Where peak demands are of relatively short duration, thisadditional storage capacity located near the consumer avoids excessivepressure drops in the line.5-2FIGURE 5-1. Air Receiver

5-34.2 Inspection and Certification of Air Receivers. Technical andadministrative procedures for inspection and certification of air receiversare contained in NAVFAC MO-324, Inspection and Certification of Boilers andUnfired Pressure Vessels. This manual also provides test and inspectionschedules and damage reporting procedures.(a) Standard Vessels. An Unfired pressure vessel is a closed vesselin which internal pressure is above atmospheric pressure, and the pressure isobtained from an external source. Safe operation of these vessels requiresadherence to the inspection frequencies and guidelines of MO–324, Inspectionand Certification of Boilers and Unfired Pressure Vessels.(b) Non-Standard Vessels. Vessels not designed and constructedaccording to the rules of the American Society of Engineer’s Boiler andPressure Vessel Code (ASME B&PV Code) are considered non-standard vessels.Because most contract inspectors are licensed to inspect according to the ASMEB&PV Code they will not certify non-standard vessels as safe for operation.Therefore, the procurement of non-ASME B&PV Code is discouraged. Whencertification of non-standard vessels must be accomplished, NAVFACENGCOMcertified Inspectors should be employed. Repair of non-standard vessels isprohibited. The inspection of non-standard vessels shall proceed in the samemanner as outlined in MO-324.5-4Section 2. COMPRESSED AIR DISTRIBUTION METHODS1 TYPES OF AIR DISTRIBUTION SYSTEMS. Compressed air is delivered toconsumers by either aboveground or underground piping systems. In manyinstances, however, life cycle economics have found that small air compressorsat the source are more feasible than a compressed air distribution system.2 DISTRIBUTION ROUTE. The minimum distance between the central compressorplant and the consumers is the preferred routing for a compressed airdistribution system; however, as with heat distribution systems, other factorsaffect the final selection of a route. These factors include the followingi terns:Characteristics of the locationFuture expansionBasements or crawl spaces available for pipingAboveground obstructions such as rivers or roadsUnderground obstructions such as piping or rockSoil Corrosivity2.1 Secondary Systems. Generally, a separate system supplies each airservice; however, economic considerations may justify installing additionalcompressors to supply air to minor branch systems.3 SELECTION OF ABOVEGROUND OR UNDERGROUND DISTRIBUTION SYSTEMS. The decisionwhether to use aboveground or underground piping shall be based on the lifecycle economics. The advantages of each system are as follows:Above-ground UndergroundLower first cost Less vulnerable targetLess maintenance Less obstruction toEasy detection of failure aboveground trafficHigher continuous operating Less unsightlyefficiency Freeze protected when buried

Longer life3.1 Other Factors. The following considerations may have an importantinfluence on the final decision of which system to employ.Permanent versus temporary useExistence of a high water tableDegree of hazard (for example, the potential danger that overheadpiping may cause to aircraft operations)Annual ownership, operation, and maintenance costs4 ABOVEGROUND DISTRIBUTION SYSTEM. An economic analysis will, in mostinstances, demonstrate the advantages of an aboveground system. Otherrequirements, such as temporary use or certain operating and localrestrictions, may dictate their use. Aboveground systems are less costly to5-5operate and maintain. The following considerations apply in the design ofaboveground distribution systems.(a) Spans. The maximum spans between pipe supports for straight piperuns depend on pipe size. Maximum spans for steel pipe and rigid coppertubing are shown “in tab’(b) Pipe Supportssimilar type clips firmlystructures may be wallsor treated wood frames.sufficient clearance ise 5-1.Pipes are usually held in place by U-shaped orsecured to support structures. The supportcolumns, brackets, concrete pedestals, steel frames,Clips fit closely around the pipe; however,permitted to allow for longitudinal movement during.normal expansion and contraction. At anchor points, the pipe is firmlyclamped to the structure. The hangers are rigid or braced, if necessary,where piping hangs from ceiling beams. This reinforcement prevents “whipping”of the pipe should a break occur while the line is under pressure.(c) Elevation Clearance. For distribution outside buildings,aboveground overhead lines may be located as little as 12 inches or as much as22 feet above grade. The clearance above roadways is from 14 to 16 feet forautomobile and truck traffic. For railroad crossings, the clearance is22 feet above grade. The minimum height for installations at low elevationsshould be sufficient to clear surface water.(d) Pitch of Aboveground Lines. Air lines are pitched down a minimum of3 inches per 100 feet of length, in the direction of airflow, to low pointswhere the condensate is collected.TABLE 5-1. Maximum Span for PipeDiameter(inches)Std. #t. CopperS t e e l P i p e Tube Type40 s K(feet & inches) (feet & inches)1/23/4

11 -1/22-1/233-1 /2456810125’-0"5’-9”6’-6”7’-6”8’-6"9’-3”10’-3"11’-0"11’-6"12’-9"13’-9”15’-6"17’-0"18'-3"3’-9"4’-3"5’-0”5’-9"6’-6"7 ’ - 3 "7’-9"8’-3"9’-0”10’-0"10’-9”( 1 i n c h = 0 . 3 0 4 8 m )5-6(e) Drip Legs. The low line points are provided with drip legs equippedwith scale pockets and automatic drain traps. When accessible, scale pocketsmay have a manual drain valve instead of an automatic drain trap. Drip legsare located at:Low pointsBottom of all risersEvery 200 to 300 feet for horizontally pitched pipe(f) Counterflow of Condensate. Where pipes must be sloped upward,causing condensate to run in a direction opposite to airflow, the pitch of thepipe is increased to a minimum of 6 inches per 100 feet.5 UNDERGROUND DISTRIBUTION SYSTEM. Selection of the route for an undergrounddistribution system involves consideration and evaluation of the followingequipment.(a) Walking Tunnel. A concrete tunnel containing piping formiscellaneous services may also be used to house compressed air pipes.

(b) Trenches. A concrete trench used for miscellaneous service pipesmay be designed to include air lines.(c) Manholes. Access to underground conduit for inspection, repair, andventilation of service piping is provided by manholes.(d) Direct Burial. Direct burial is the method most commonly used forcompressed air distribution lines. Because this type of constructiongenerally lowers the air temperature causing additional condensation, it isimportant that the piping be properly pitched to collect condensation at driplegs. Drip legs can be located in building basements; however, manholes maybe required at low points of long distribution systems to house moisturetraps. Corrosion control by cathodic protection may be required depending onsoil corrosivity.(e) Pipe Covering. Buried compressed air lines generally require noinsulation. However, they should be shop coated, wrapped: tested, and handledin accordance with NAVFAC Specification 34Y (Latest Revision), BituminousCoating for Steel Surfaces.(f) Pitch of Underground Systems. Air lines are generally pitched downa minimum of 3 inches per 100 feet of length, in the direction of airflow, toprovide easy drainage of condensate.(g) Drip Legs. Refer to section 2, paragraph 4(e). In horizontallypitched buried pipes where traps are inaccessible, drip legs are located atintervals of not over 500 feet.(h) Counterflow of Condensate. Refer to section 2, paragraph 4(f).6 PIPING.6.1 Piping Design. When practical, pipelines distributing compressed air tonumerous branches or service outlets in a large area should form a closed5-7loop. This maintains maximum pressure at branches and outlets and providestwo-way distribution to consumers. The use of a closed loop equipped withconveniently located segregating valves permits a partial shutdown of thesystem for inspection or repairs. Generally, provisions are made for bleedingeach part of a loop between segregating valves. The loop pipe should be ofsufficient size to prevent an excessive pressure drop at any outlet regardlessof the direction of airflow around the loop. Branches shall be at the top ofthe main to prevent carryover of condensate and foreign matter.6.2 Piping Materials.6.2.1 Low-Pressure and Medium-Pressure Systems. Black steel pipe inappropriate thicknesses conforming to pipe Schedule 40, ASTM A 53 or A 120 isused in these systems and is joined preferably by welding. For specialconditions, stainless steel pipe and copper tubing with appropriate fittingsare also used. Connections to removable equipment are always flanged, exceptwhen using small threaded pipe. In all cases, pipes, fittings, and valvesshall be in accordance with NAVFAC Specification 21Y (Latest Revision), SteamPower Plant, Heating, and Ventilating Equipment and Piping; andANSI/API 510-1983, Pressure Vessel Inspection Code - Maintenance, Inspection,Rating, Repair, and Alteration.6.2.2 High-Pressure Systems. Seamless steel pipe conforming to ASTM A 53 orA 120, with Schedule determined in accordance with ANSI/API 510-1983, iscommonly used for high-pressure air systems. Except in very small sizes, buttwelded fittings are employed. Screw fittings, when used, have their endssealed by fillet welds and exposed pipe threads covered with weld. Unions are

of the forged steel ground joint type. When economic considerations dictateits use, small systems may employ stainless steel pipe with special fittingsto assure a continuous supply of high quality air. Shore activities,particularly torpedo workshops, frequently require copper tubing,Silver-brazed, bronze fittings and valves, and bronze unions with steel ringnut, plastic ring gasket, and silver-brazed ends are used with copper tubing.Pipes and fittings shall comply with NAVFAC Specification 21Y (LatestRevision), Steam Power Plant, Heating, and Ventilating Equipment and Piping;and ANSI/API 510-1983, Pressure Vessel Inspection Code - Maintenance.Inspection, Rating, Repair, and Alteration.6.3 Valves. Refer to chapter 6 for description and application of thedifferent types of valves used in air distribution systems. Globe valves usedin high-pressure horizontal air lines should be installed so that the stemprojects horizontally. This prevents restrictions to line drainage whichcould be caused by the elevated valve seat. If the valve must be installedwith the stem in the vertical position, or when the valve interferes with linedrainage, a drain connection for the pocketed space should be provided.6.4 Expansion and Contraction. Expansion and contraction of pipes carryingcompressed air is normally not a serious problem. However, consideration mustbe given to failure of an aftercooler which would allow air at elevatedtemperatures to enter the system and cause thermal expansion. Piping in theimmediate vicinity of the air compressors can also be hot enough to warrantcareful checking of flexibility. Wherever possible, expansion is controlledby a change in direction of pipe runs or by the use of expansion bends and5-8loops. In low-pressure systems, various types of corrugated pack-less typeexpansion joints or slip-packed joints can be used.

Compressed Air

The compressed-air systems provide service air and instrument air throughout the plant. The following guidelines apply to the design and layout of these systems:

● Refer to the compressor manufacturer’s instruction manual for the recommended relative lengths of intake and discharge piping versus compressor revolutions per minute (rpm).

● The compressed-air system equipment arrangement and piping design should be such that the air receiver is the lowest point in the system and any condensate in the system will drain to the air receiver, particularly during periods of shutdown when large amounts of condensate can form. The point here is to preclude any possibility of condensates draining back to the air compressor, where it could cause extensive damage. The compressor discharge piping should be as short and direct as possible through the aftercooler and into the air receiver. The compressed-air system distribution lines and risers should originate from a separate outlet connection on the air receiver and should be sloped back to the air receiver.

● Compressed-air line header branches should have vertical risers and be drained at their terminations.

● Individual service branches should be taken off the top of the headers.

4.9.2 Steam pipingSteam piping shall be run to prevent pockets. Condensate shall be collected at low points by using astandard steam trapping system.

Drain points shall be from the bottom of the header and steam take-offs from the top. STEAM DISTRIBUTION SYSTEM. Consumers may be located in several buildingsor a group of buildings where steam is required for space heating and/orprocess work. For purposes of this manual, a steam distribution systemconsists of the following equipment:Steam piping required to transport steam from a central steamgenerating plant to consumersPiping required to return condensate to the generating plantEquipment, instrumentation, and related facilities required toserve the above described purposes3 SUPPLY PRESSURE. Steam supply systems are categorized as either lowpressuresystems or high-pressure systems.3.1 Low-Pressure Steam. Low-pressure steam, O to 15 psig, is used for spaceheating (unit heaters, radiators, connectors, heating coils, or other steamheating devices), snow melting, cooking, and domestic hot water heating. Itis distributed from a central plant or mechanical room to a multiple buildingi n s t a l l a t i o n . The advantages of low-pressure vice high pressure steam are:Small distribution losses, due to the relatively low temperature ofthe steamSmaller losses and trouble from leakage, traps, and venting3-1Simplified pressure reduction at buildingsSubstitution of standard cast iron fittingsLess maintenance3.2 High-Pressure Steam. High-pressure steam, above 15 psig, is used forindustrial purposes, process work, hospital uses, laundry machinery, and drycleaning. For extensive outside distribution, high-pressure steam at or above100 psig is commonly employed. Figure 3-1 illustrates a schematic flowdiagram of a steam distribution system. In this system, steam is generated at100 psig in a central steam generating station and then distributed toconsumers. The diagram shows conversion of high-pressure 100-psig steam to40-psig low-pressure steam for hospital uses. Reduction to 5-psig steam forspace heating purposes is also shown. Steam for laundry machinery, however,is used at 100-psig pressure. System components such as valves, traps,pressure reducing valves, pumps, and other required equipment are consideredin following chapters. The main advantages of high-pressure steam vice lowpressure steam distribution are:Smaller pipe sizesAvailability for purposes other than heatingMore flexibility in design for velocity and pressure drops4 DISTRIBUTION ROUTE. The piping route for steam distribution systems isselected to obtain the minimum possible distance from the central generatingstation to the demand centers. The following factors affect selection of theroute (for additional factors refer to NAVFAC DM-3, Design Manual, MechanicalEngineering):Characteristic of the locationFuture growthBasements or crawl spaces available for piping

Existing tunnels or trenches available for the systemAboveground obstructions, such as rivers or roadsUnderground obstructions, such as piping or rockSoil Corrosivity

FIGURE 3-1. Schematic Flow Diagram of a Typical Steam Distribution System3-3Section 2. STEAM DISTRIBUTION METHODS1 TYPES OF DISTRIBUTION SYSTEMS. Two main systems are used for distributionof steam: aboveground distribution systems and underground distributionsystems. The decision to select an aboveground system or an undergroundsystem depends on the following factors:Permanent against temporary useHigh water table ground conditionsDegree of hazard (as when the overhead piping may cause a potentialdanger to aircraft or other operations)2 ABOVEGROUND DISTRIBUTION SYSTEMS. Aboveground distribution systems shallbe selected whenever practical. Due to their ease in detecting when and wheremaintenance is required, NAVFAC prefers this type of installation. Withproper maintenance, this type of system is the most energy efficient and coste f f e c t i v e .2.1 Advantages of Aboveground Systems. The main advantages of using

aboveground vice underground distribution systems are:Lower initial costLess maintenanceEasy detection of failureHigher continuous operating efficiencyLonger lifeReduced external corrosion2.2 Distribution Lines. Distribution lines usually consist of abovegroundconduits supported as follows:Low Elevations. For aboveground systems installed at lowelevations, the conduits are supported on concrete pedestals, steelframes, or treated wood frames. Supports are spaced 10 to 15 feet oncenters depending on pipe size.High Elevations. At higher elevations aboveground, conduits may besupported on wood, steel pipe, H-section steel poles with crossarms,or steel frameworks fitted with rollers and insulation protectionsaddles.Long Spans. When long spans are required, conduits are supportedby cable suspension with supports up to 50 feet on center.3-42.3 Pipe Covering.Never stand or sit on aluminum jackets. Severe damage to theinsulation will result.Aboveground piping is covered with insulation (refer to chapter 7) and thenfurnished with a protective covering of one layer of impregnated roofing feltand an aluminum jacket. This covering provides protection against weather andmechanical damage. The felt is applied with longitudinal and circumferentialseams lapped not less than 4 inches and secured with stainless steel staples.The aluminum jackets, longitudinally corrugated for strength, are not lessthan 0.017-inch thick. The longitudinal and circumferential seams are lappednot less than 2 inches. Jackets are secured with aluminum strips or withstainless steel sheet metal screws set on not more than 5-inch centers on thelongitudinal and circumferential seams.2.4 Road Crossings. Road crossings are often made by transition to an underground system which usually serves as an expansion loop.2.5 Elevation Clearance. Conduits may be located as little as 12 inches oras much as 22 feet above grade. The clearance above roadways is from 14 to 16feet for automobile and truck traffic. For railroad crossings the clearanceis 22 feet above grade.2.6 Pitch of Aboveground Steam Lines. Steam lines are pitched down at aminimum of 3 inches per 100 feet of length in the direction of steam flow.Often counterflow of condensate within the steam pipe will occur in a portionof a pipeline because of steam flow reversal in a loop system. In thesecases, that portion of the pipe is pitched a minimum of 6 inches per 100 feetand pipe diameters are increased by one standard pipe size. Increasing theflow area reduces the steam velocity in the pipe and prevents retention ofcondensate and water hammer.3 UNDERGROUND DISTRIBUTION SYSTEMS. Underground distribution systems shallonly be used where local conditions prohibits the use of above-ground systems;for example, when an above-ground system would create a hazard to aircraft orother operations. Underground systems are more costly to install and more

difficult to maintain than the above-ground systems. Justification, statingthe conditions which prohibits the use of above-ground systems is required onall MCON and special projects involving steam distribution systems. Thisincludes repair by replacement type projects where the existing distributionsystems are underground.3.1 Advantages of Underground Systems. The main advantages of usingunderground distribution systems follow.They are a less vulnerable target.3-5They do not interfere with aboveground traffic.They are less unsightly.The piping is protected from freezing when buried below the frostl i n e .

---pitch and conduit system details (steam 1 pdf)

CONDENSATE RETURN. In steam distribution systems that use ferrouscondensate return lines, it is customary to provide a separate conduit for theinsulated condensate return piping. This is done because the return piping isoften subject to corrosion which makes its life considerably shorter than thelife of the steam pipes. When nonferrous condensate return lines are used,they are enclosed with the steam lines in the same conduit. In such cases,the condensate return lines are insulated when required by economicconsiderations.5 PIPING. Steam distribution systems generally use black steel pipe. Thecondensate return lines can be extra strong wrought iron, extra strong steel,or copper. Joints for steel piping are usually welded, except those inmanholes, which may be flanged. Copper piping is provided with brazedj o i n t s . For information on valves, fittings, and associated equipment referto chapter 7.

The power industry, through its many years of experience, has found that piping arrangements and layout can influence the functionality of a piping system. This section will present specific system guidelines and considerations that will enable the piping designer to minimize that influence.

Main Steam and Hot and Cold Reheat

In any power plant, be it a base-loaded electric power generation station or an industrial facility power plant, the main steam system is the backbone of the installation since it ties together the two most important and most costly pieces of equipment, the steam generator and the turbine, and is also usually the first system designed, giving it the preference in space allocation and routing. The recommendations of the following references should be incorporated in the design of the main steam and reheat steam piping systems.

1. ANSI/ASME TDP-1-1985, Recommended Practices for the Prevention of Water Damage to Steam Turbines Used for Electric Power Generation (Fossil), American Society of Mechanical Engineers, New York.

2. ANSI/ASME TDP-2-1985, Recommended Practices for the Prevention of Water Damage to Steam Turbines Used for Electric Power Generation (Nuclear), American Society of Mechanical Engineers, New York.

Adherence to the following guidelines will ensure that the system performs its intended function:

● All piping in this service should be sloped down a minimum of ¹⁄₈ in/ft (10 mm/m), in the direction of flow. Extensive evaluation and design are required for lines that do not slope in the direction of flow to ensure that condensate is collected and drained adequately.

● The final design of the main steam and hot reheat lines should be reviewed, with consideration for thermal growth, to determine the location of any necessary lowpoint drains and to ensure that the system can be completely drained in both the hot and cold conditions. When these lines are split into more than one branch into the turbine, each branch should be reviewed for low points. Provide a drain  connection in each branch as close as possible to the turbine stop valve. All drain lines and large valve drain ports should have an inside diameter of not less than 1 in (25 mm), to prevent plugging. Main steam piping drains should not be piped together with any other drains from the boiler. In addition, this review should ensure that no condensate can collect in any undrained portion of the system during shutdown.

● Provide a drain pot at the low point of each cold reheat line, which should be fabricated from NPS 6 (DN 150) or larger pipe and be no longer than required to install the level-sensing devices. Each pot should be provided with a minimum NPS 2 (DN 50) drain line and a full-sized, full-ported automatic power-operated drain valve. Each drain pot should be provided with a minimum of two level sensing devices.

● Steam lines that are fitted with restricting devices such as orifices or flow nozzles should be adequately drained upstream of the device.

● Valves in all steam services should be installed with the valve stem in the vertical upright position to prevent the entrapment of fluid in the bonnet. Where this is not practical, the stem may be positioned between the vertical and horizontal positions, but in no case below horizontal.

● Main steam safety relief valves should be fitting-bound to the main steam headers.

● Sufficient space should be provided around any steam line to allow for insulation, pipe supports and anchors, thermal growth, machine welding, and maintenance repairs and replacements.

Turbine Extraction Steam

Most steam turbines are provided with one or more low- to intermediate-pressure steam extraction points either for boiler feedwater heating or for industrial process service and heating. These systems are extremely critical, particularly from the standpoint of water damage, and must be designed in accordance with the following standards and guidelines:

ANSI/ASME TDP-1-1985, Recommended Practices for the Prevention of Water Damage to Steam Turbines Used for Electric Power Generation (Fossil), American Society of Mechanical Engineers, New York (Ref. 1).

ANSI/ASME TDP-2-1985, Recommended Practices for the Prevention of Water Damage to Steam Turbines Used for Electric Power Generation (Nuclear), American Society of Mechanical Engineers, New York (Ref. 2).

● The routing should be as short and as direct as possible with consideration for thermal growth and piping flexibility.

● Extraction steam piping should be sloped down a minimum of ¹⁄₈ in/ft (10 mm/m), in the direction of flow. Extensive evaluation and design are required for lines that do not slope in the direction of flow to ensure that condensate is collected and drained adequately.

● Bleeder trip valves must be located as close to the turbine extraction point as possible, while at the same time keeping the total volume of the system within the turbine manufacturer’s recommendations.

● When extraction steam piping is routed through the condenser neck, an expansion joint must be provided in each line and located at the turbine nozzle. The bleeder trip valves in these lines must be located just outside the condenser neck.

● A drain should be located at the low point in the extraction pipe between the turbine and block valve and routed separately to the condenser.Apower-operated drain valve should be installed in this line that opens automatically upon the closure of the block valve in the extraction pipe.

● There should be no bypasses around the extraction line shutoff or non return valves.

● Unavoidable vertical loops which create low points in the piping downstream of the bleeder trip valves must be provided with continuously drained drip pots.

● Provide a minimum of five diameters of straight pipe downstream of all bleeder trip valves.

● Provide maintenance access to all bleeder trip valves including any miscellaneous platforms, if needed.

Condensate

The condensate collection system from the condenser hotwell presents a unique set of parameters since we are dealing with water at slightly elevated temperatures and at a vacuum pressure. These conditions make the condensate pump suction piping susceptible to flashing and cavitation. The following guidelines apply to the design of condensate pump suction and discharge piping:

● Where two or more condensate pumps are used, the individual runs to each pump must be similar, and if a suction manifold or header is used, the individual pump suction lines from that manifold or header must be similar.

● When the manifold or header is larger than the pump suction size, the manifold or header should be made up of full-sized tees and eccentric reducers, flat side up.

● Each individual pump suction run should be sloped down a minimum of ¹⁄₈ in/ft (10 mm/m) toward the pump and be self-venting back to the condenser.

● Provide a minimum of three to four diameters of straight pipe in the pump suction line; in addition, these lines must be fitted with expansion joints and startup strainers.

● The condensate pump discharge check valve must be located below the hotwell water level and be continuously flooded.

● The discharge header outlet should not be located between the pump discharge connections to the header, to avoid a counter flow condition.

● The condensate pump recirculation control valve should be located at the condenser nozzle.

Feedwater

The boiler feedwater pumps normally take suction from the deaerator storage tank, discharge to the feedwater heaters, and then supply the boiler. Here, too, the designer has to deal with the possibility of flashing fluid and must ensure that the deaerator storage tank is located at an elevation that will provide sufficient net positive suction head (NPSH) at the pump. The following guidelines apply to the design of this piping:

● The pump suction piping from the deaerator storage tank should drop vertically, avoiding any long horizontal runs of pipe. If short horizontal runs are unavoidable, they should be angled vertically down.

● A minimum of 3 diameters of straight pipe is required at the pump suction. The pump suction strainer may be located in this run of pipe.

● If a reducer is required at the pump suction, it must be eccentric and installed with the flat side up.

● The feed pump discharge swing check valves should be located in horizontal runs of pipe only.

● The feed pump recirculation line control valve should preferably be located at the deaerator storage tank. Horizontal runs are to be avoided in this line at the tank. If the control valve is located in a branch from the pump discharge, the line downstream of the valve must be continuously flooded.

Turbine Drains

This system consists of the turbine casing drains from the turbine to the condenser, a drain collection manifold at the condenser, or other drain vessel as indicated on the system P&ID. The designer should comply with the following standards and consider the guidelines listed below for the physical design of these drains:

ANSI/ASME TDP-1-1985, Recommended Practices for the Prevention of Water Damage to Steam Turbines Used for Electric Power Generation (Fossil), American Society of Mechanical Engineers, New York (Ref. 1).

ANSI/ASME TDP-2-1985, Recommended Practices for the Prevention of Water Damage to Steam Turbines Used for Electric Power Generation (Nuclear), American Society of Mechanical Engineers, New York (Ref. 2).

● Turbine drain lines and valve ports should be sized for the maximum amount of water to be handled under any operating condition, but in no case may they be less than NPS ³⁄₄ (DN 20).

● Drain lines should be designed for both hot and cold conditions and should slope continuously downward in the direction of flow. Flexibility loops, when required, should be in the plane of the slope or in vertical downward runs.

● Continuous drain orifices, when used, should be located and designed so that they may be cleaned frequently and will not be susceptible to plugging by debris.

● Steam traps are not satisfactory as the only means of draining critical lines; however, they may be used in parallel with automatically operated drain valves.

● No part of any drain line may be below its terminal point at the condenser, drain collection header, or other drain vessel.

● Only drain lines from piping systems of similar pressure may be routed to a common manifold.

● All drain and manifold connections to the condenser must be above the maximum hotwell water level.

● Drainage from other vessels, such as feedwater heaters, steam jet ejectors, and gland steam condensers, that drain water continuously must not be routed to turbine cycle drain manifolds.

● Drain lines should be connected at a 45 angle to the manifold axial centerline with the drain line discharge pointing toward the condenser. Drain line connections at the manifold should be arranged in descending order of pressure, with the highest pressure source farthest from the manifold opening at the condenser.

● Drain connections to flash tanks must be above the maximum water level in the tank.

● Drains from the upstream and downstream sides of shutoff valves must not be interconnected.

● Drain lines in exposed areas should be protected from freezing.

● All turbine drain drawings must be reviewed and approved by the turbine supplier.

Heater Drains

The heater drains system consists of the feedwater heater drains from one heater to another at a lower pressure, to a drain tank, or to the dump line to the condenser. The designer should comply with the following standards and consider the guidelines listed below for the physical design of these drains:

ANSI/ASME TDP-1-1985, Recommended Practices for the Prevention of Water Damage to Steam Turbines Used for Electric Power Generation (Fossil), American Society of Mechanical Engineers, New York (Ref. 1).

ANSI/ASME TDP-2-1985, Recommended Practices for the Prevention of Water Damage to Steam Turbines Used for Electric Power Generation (Nuclear), American Society of Mechanical Engineers, New York (Ref. 2).

● Drain piping from feedwater heaters without an internal drains cooler must immediately drop vertically to provide as much static head as possible upstream of the heater level control valve. Thereafter any horizontal runs must be sloped down a minimum of ¹⁄₄ in/ft (20 mm/m) in the direction of flow.

● Drain piping from feedwater heaters with an internal drain cooler may be routed horizontally without sloping upon leaving the heater.

● Heater level control valves should be located as close as possible to the receiving vessel, with consideration for ease of access and maintenance.

● The heater drain system arrangements must be coordinated with the system engineer for analysis to ensure that single-phase water flow is maintained upstream of the heater level control valves and to determine where downstream velocities may require tees and target plates in lieu of elbows for minimizing erosion.

● Heater drain dump lines should enter the condenser at approximately the horizontal centerline of the tube bundle. This location should be coordinated with the condenser manufacturer, who will provide the necessary baffle plates to prevent impingement on the condenser tubes.

● Only long-radius elbows should be used in heater drain piping.

● The use of reducers should be avoided, except at the control valves, which are generally smaller than the line size.

4.9.3 Utility stationsUtility StationsProvide and locate utility stations with water, steam, or air as indicated below:All areas should be reachable with a single 50 foot (20m) length of hose from the station. Provide water outlets at grade level only, in pump areas, and near equipment that should be water washed during maintenance.Provide steam outlets at grade level only in areas subject to product spills, and near equipment that requires steaming out during maintenance.Provide air outlets in areas where air-driven tools are used such as at exchangers, both ends of heaters, compressor area, top platform of reactors, and on columns at each manway.Hose, hose rack, and hose connections should be provided by the client or be purchased to match the clients existing hardware.

Utility stations shall be provided as required for air, water, steam/hot water and nitrogen. Eachstation shall be numbered and located in the general working areas at deck level. Freshwater,seawater and plant air systems shall be equipped with hosereels. Nitrogen stations shall not belocated inside enclosed areas. Nitrogen hoses shall be installed if required (for reference,see L-003). Different types of couplings shall be used for air and nitrogen.4.9.4 Pressure relief pipingPiping to pressure relief valve inlet shall be as short as possible.Piping design, layout and stress analysis L-002Rev. 2, September 1997NORSOK standard Page 12 of 17When relief valves discharge to atmosphere, the elevation at the top of the discharge line shalltypically be 3000 mm above all adjacent equipment. This is to keep adjacent equipment outsideplume area. Discharge tail pipes shall have a drain hole at the low point of the line.Relief valves discharging to a flare system shall be installed so as to prevent liquid being trapped onthe outlet side of the valve. All relief lines and headers shall be designed to eliminate pockets, but ifa relief valve must be located at a lower elevation than the header, an automatically operated drainvalve shall be installed at the valve outlet and piped to a collecting vessel or closed drain.Relief valve headers shall slope towards the knock-out drum, taking into account anticipated deckdeflection and platform tilt during operation. Pockets are to be avoided, but where a pocket isunavoidable, some approved means of continuous draining for the header shall be incorporated.

Unless specifically noted on the P&ID all branch connections on relief and blowdown systems shallbe at 90° to the pipe run. Should there be a special requirement for a particular branch to enter aheader 45°, this shall be highlighted by process engineers on the P&ID.4.9.5 Open drain systemsDrains shall have slope as specified on the P&ID's. Open drain branch connections shall all be 45°.Rodding points shall preferably be through drain boxes and change of direction shall be evaluatedagainst flushing requirements, where the total change of direction is greater than 135°.4.9.6 Pneumatic conveyingPneumatic conveying piping shall be designed according to and approved by the pneumaticconveying system manufacturer. Purge connections shall be easy accessible to avoid waste of timewhen plugs occur.4.9.7 Fire/explosion protectionAll project accidental load requirements shall be met (ref. S-001).4.9.8 Firewater distribution systemThe layout of the firewater distribution system shall be carefully designed with respect to hydraulicpressure drop.Deluge nozzles branch off shall be located away from the bottom of the header to avoid plugging ofnozzles.Location of nozzles shall be as specified by the safety discipline. Necessary deviations to avoidobstructions etc. shall be approved by the safety discipline.Dead end headers shall be avoided.4.9.9 Lube, seal and hydraulic oil systemsLube, seal and hydraulic oil systems shall have flanges and blind flanges on header ends for picklingand hot oil flushing.

Hot water:SCOPE Direct buried conduit systems shall be installed, maintained, andrepaired in accordance with the Manufacturer’s Approved Brochure and NAVFACGuide Specifications NFGS-15705, Underground Heat Distribution Systems(Prefabricated or Pre-Engineered Types). Systems shall have a Letter ofAcceptability issued by Federal Agency Committee on Underground HeatDistribution Systems. The Letter of Acceptability is signed byrepresentatives of federal agencies participating in the committee and statingthat the supplier’s system is approved for use for the site ground-water .conditions, operating temperature, and soil classification(s) indicated.Shallow concrete trench systems shall be installed in accordance with

NFGS-15751, Heat Distribution System Outside of Buildings (Concrete ShallowTrench Type). Hot water can be distributed more efficiently and costeffectively than steam. For this reason hot water should be utilized oversteam wherever feasible. Engineering Field Divisions shall assist andactivities shall assure that operation and maintenance of hot waterdistribution systems are performed. The Power Principles Video TrainingProgram shall provide further assistance to all concerned.2 HTW HEAT TRANSMISSION. High temperature water (HTW) is an alternate mediumto steam for conveying heat to customers located some distance from thegenerating plant. HTW can be efficiently generated and distributed, easilycontrolled, and accurately measured. It is distributed in a closed systemfrom the generating plant to customers within a radius of 6 miles; although,with booster pumps-this distance can be extended.little energy loss except for line heat losses ofdistribution piping.3 HTW DISTRIBUTION SYSTEMS.3.1 Definition. An HTW distribution system consequipment:The system experiences3°F to 8°F per mile ofists of the following(a) Piping to transport high temperature supply water from a central HTWgenerating plant to consumers;(b) Piping to return the high temperature water to the generating plant;(c) Equipment, instrumentation, and related facilities to safely andefficiently accomplish these tasks.3.2 Types of HTW Distribution Systems.(a) Low Temperature Water System (LTW). A hot water heating system operatingwith a pressure of approximately 30 psig and a maximum temperature of 250°F.(b) Medium Temperature Water System (MTW). A hot water heating systemoperating at temperatures of 350°F or less, with pressures not exceeding150 psig. The usual supply temperature is approximately 250 to 325°F.4-1(c) High Temperature Water System (HTW). A hot water heating systemoperating at temperatures over 350°F and pressure of approximately 300psig. The usual maximum supply water temperature is 400 to 450°F.(d) Selecting type of Hot Water Distribution System. Systems mustmaintain adequate pressure and temperature and assure uniform flow of water tocustomers. Hot water generators consist of natural circulation boilers orforced circulation boilers. Since hot water distribution systems are moreefficient than steam distribution systems, they should be selected wheneverpractical. The lower the temperature required the more efficient the systemshould operate due to the lower temperature differential between the hot waterand piping’s external temperature. Lower temperature systems are less costlyto construct as well. All projects calling for the replacement or newinstallation of a heating system shall include a life cycle economic analysisof steam vs LTW, MTW, and HTW distribution systems, and justification, statingthe conditions which prohibits the use of above-ground systems on all MCON andspecial projects. This includes repair by replacement type projects where theexisting distribution systems’ are steam and/or underground. The followingfactors will be among those considered in the analysis:

(1) Economic advantage of thermal storage of the hot water systemin sizing of equipment such as boilers, pumps, and piping.(2) Operation and maintenance costs of hot water distributionsystem versus steam distribution system.(3) Customer requirements of temperature or pressure served moreeconomically by steam or hot water.(4) Replacement or renovation of existing plant and distributionsystem compared with construction of new plant and/or distribution system.Comparison to be on a life cycle basis.(5) Prevalence of skilled steam plant or hot water plant operatorsin area, especially in remote locations.(6) Complexity of controls and ability of steam to maintain varyingor constant temperature conditions through the assigned or existing heattransfer equipment.3.3 Heat Storage Capacity. A useful characteristic of HTW systems is thelarge heat storage capacity. This property gives the system a thermal flywheeleffect which permits-close temperature control and more rapid responseto changing load demands. In fact, the system acts as an accumulator of theheat generated: and helps equalize the heating load on the boilers. Table 4-1shows a comparison of the heat storage capacity of water and steam fordifferent pressures and temperatures. The variations of density and volume ofHTW with changes in temperature are shown in table 4-2.3.4 Temperature Differential. To take full advantage of the high heatcontent of HTW, distribution systems are designed for the largest temperature4-2TABLE 4-1. Heat Storage Comparison TABLE 4-2. Density and Volumeof HTW and Steam Variations of HTWWith TemperatureTotal Heat Content Saturated HeatTempera- (Btu/ft’) Contentture Absolute RatioPressure(°F) HTW/ (psia) HTW Steam Steam250 29.82 12,852 84.22 152.6260 35.43 13,378 99.23 134.8270 41.86 13,910 116.35 119.5280 49.20 14,430 135.77 106.3290 57.56 14,946 157.73 95.17300 67.01 15,449 182.44 84.68310 77.68 15,950 210.18 75.88320 89.66 16,446 241.19 68.19330 103.06 16,930 275.76 61.39340 118.01 17,411 314.18 55.42350 134.63 17,878 356.76 50.10360 153.04 18,342 392.29 55.70370 173.37 18,803 455.73 41.26380 195.77 19,251 513.10 37.52390 220.37 19,685 575.73 34.21400 247.31 20,116 644.55 31.21410 276.75 20,545 719.82 28.54420 308.83 20,949 802.07 26.09430 343.72 21,350 891.76 23.94440 381.59 21,750 989.48 21.98450 422.6 22,170 1,095.79 20.23SaturatedTemperature

70250260270280290300310320330340350360370380390400410420430440450Density( l b / f t ' )62.3058.8258.5158.2457.9457.6457.3156.9856.6656.3155.9655.5955.2254.8554.4754.0553.6553.2552.8052.3651.9251.50Spec. Volumef t ' / l b0.016060.017000.017090.017170.017260.017350.017450.017550.017650.017760.017870.017990.018110.01823

0 .0183b0.018500.018640.018780.018940.019100.019260.01940difference between the supply and the return water consistent with economicalconsiderations. The amount of heat extracted from a given amount of watereffects the temperature differential between the supply and the return water.The greater the temperature difference, the more heat obtained per unit ofwater. Higher heat extraction permits cutting down the flow rates, whichreduces the size requirements of the distribution pipes and pumps, and thepump horsepower. The usual temperature differential range for an HTW systemis 100°F to 150°F. A maximum differential of 200°F is practical with forcedcirculation boilers. For natural circulation boilers, a maximum differentialof 250°F is considered practical.4 EXPANSION TANKS. All HTW systems require expansion tanks to allow forvariations in the system water volume caused by temperature changes. Volumeexpansion is not based on cold water conditions because that extreme variationonly occurs when starting up cold. Rather, the tank is sized to handlechanges in water volume resulting from normal load changes. In general, thefollowing factors are considered in sizing a tank.Sludge and suction space at the bottom of the tank. From 6 to 9inches of elevation are reserved for this purpose.4-3Reserve storage of not less than 30 seconds supply to all pumpsconnected to the tank.Space for water expansion due to temperature changes. This dependson the supply and return temperature limits, and on the total amountof water in the system.Space for operation of level alarms and overflow. Normally, l-footdepth is reserved for this purpose.Space pressurization above the overflow level. When steampressurization is used, this space amounts to 20 percent of thevolume reserved for water expansion.The ratio of diameter to length is kept towith a minimum tank diameter of 6 feet.4.1 Expansion Tank Connections. The following connectiprovided for expansion tanks.3.5 approximately,ons are usuallyDraining and filling connections used to completely drain the tankor to fill it with water after a shutdown.Supply piping for steam pressurized tanks. The boiler water shouldbe fed horizontally below tank water level through independent pipeleads from each boiler.Pump suction connections usually provided with vortex eliminators.Safety valves for protection against overpressure.Blowoff connections to rapidly remove large quantities of waterresulting from volume expansion when starting up a system, to reduce

water concentration, and to aid in the removal of sludge.Overflow connections.Connections for thermometers, pressure gauges, water gauge glasses,level controls, and alarms for proper operation and control.5 PRESSURIZATION. The design boiler pressure must be high enough to producesaturated water at a temperature substantially above the design supply watertemperature. This is required to prevent a flashing of water into steamshould the system flow pressure drop. The temperature difference, 20°F to30°F approximately, can be obtained by cooling the water below the saturationtemperature before it enters the circulation system pump. Additionally, theexpansion tank of a steam pressurized system is usually located about 16 feetabove the boiler outlet header, and this additional head provides a safemargin above the saturation temperature. The two basic methods of systempressurization that are used to keep the HTW in its liquid state are the steamcushioned system, and the inert gas pressurized system.5.1 Steam Cushioned System. In this system, the steam present at saturatedwater temperature conditions in the expansion tank is used directly4-4to impose a pressure cushion. The elevation of the tank above the circulationsystem pump provides the required head to prevent flashing of the supply hightemperature water.5.2 Inert Gas Pressurized System. In this system an inert gas, usuallynitrogen, is used in the expansion tank to impose a pressure higher than themaximum saturated pressure of the high temperature water. The expansion tankcan be located at floor level. When an inert gas is used to pressurize thesystem, the expansion tank is generally connected to the main return line andno circulation takes place in the tank. Compressed air is never used forpressurization because absorption of oxygen by water would occur withunacceptable corrosion of the metallic elements of the system.6 PUMPING SYSTEMS. Two main pumping systems that are in use as a result ofthe different pump arrangements are the combined pumping system and theseparate pumping system.6.1 Combined Pumping System. In this system the same pumps are used tocirculate water through both the HTW generators and the system. In general,these systems are used where the circulation rate in a single distributionsystem is fairly constant, and heat load capacities do not exceed 31,500,000Btu per hour. Figure 4-1 illustrates a steam pressurized HTW combined pumpingsystem. Combined pumping systems are generally provided with the followingequipment.FIGURE 4-1. Steam Pressurized HTW Combined Pumping System4-5(a) Automatic Bypass Control Valve. This valve is installed at thedischarge of the combination pumps, bypassing the distribution system, and isactivated by the boiler inlet waterflow rate. The purpose of the valve is toensure minimum required boiler circulation at all times, regardless of loadconditions. The valve is provided with a manual bypass.(b) Temperature Control Valve. This valve is installed in the blendingline to the suction of the combination pumps. Its purpose is to cool waterentering the pumps, below the point at which flashing may occur. Also, itserves to regulate the HTW supply temperature by mixing the hot water from theexpansion tank with a portion of the cooler high temperature water return.

The valve is furnished with a manual bypass.(c) Water Flowmeters. These meters are provided forwaterflow to each boiler inlet piping so that all boiler flequalized.(d) Automatic Closing Valves. These valves are provimeasurement ofows can beded to isolate theusing end of the system should a major break occur in the supply or returnmain. In such a case, the automatic bypass control valve referred to in (a)above operates to direct the discharge water from the combination pumps to theboiler inlet. This maintains the required waterflow through the HTWgenerators and prevents tube burnout.(e) Pressure Differential Switch. This switch is installed across thepump suction and discharge headers to terminate firing when the pressuredifferential falls below a preset minimum. Often, a minimum flow switch ineach flowmeter is used instead, which terminates firing when insufficientwater flows through the boiler.(f) Combustion Control Interlocks. The pump starters are interlockedwith the combustion control to prevent boiler operation without pump operation.6.2 Separate Pumping System. In these systems, water is circulated throughthe boiler by individual boiler recirculation pumps, while separatecirculating pumps circulate the water through the distribution system. Thisis a more flexible arrangement which assures circulation through the boilerIndependently of the water circulation through the distribution circuit.Figure 4-2 illustrates a nitrogen pressured HTW separate pumping system.Separate pumping systems are used for the following conditions:Where heat loads vary greatly and adequate flow cannot be obtainedunder minimum load conditionsWhere it is desirable to operate a distribution system for shortperiods independently of the boilersWhere several zoned distribution systems are required, each withits own set of system circulating pumpsWhere the heat load is over 31,500,000 Btu per hour and the systemis economically justified4-6FIGURE 4-2. Nitrogen Pressurized HTW Separate Pumping SystemWhere it is mandatory that a boiler circulating system be isolatedfrom the distribution system6.3 Alternate Equipment. Separate pumping systems are usually provided withthe following equipment.(a) Temperature Control Valve. This automatic valve is installed in theblending line to the suction of the system csame purpose described for combined systemsfurnished with a manual bypass. The purposewhich is installed in the return line supplypumps, is to create a pressure drop, therebytemperature control valve.irculation pumps. It serves thein 6.1(b) above. The valve isof the manual throttling valve,

ing the boiler recirculationfacilitating operation of the(b) Automatic Closing Valves. These are motor operated valves providedto isolate the using end of the system should a major break occur in thesupply or return mains. They are set to close when the waterflow exceeds apredetermined value.4-7(c) Water Flowmeters. These meters are used for the same purposedescribed in 6.1(c) above for combined pumping systems.(d) Minimum Flow Switch. A minimum flow switch is incorporated in eachboiler flowmeter to terminate firing when the waterflow drops below a safelevel.(e) Combustion Control Interlocks. The starting switches of the boilerrecirculation pumps are interlocked with the combustion control of all boilersto prevent boiler operation without pump operation.6.4 Zoning. When economically justified, zoning arrangements of thedistribution circuits are provided where various groups of buildings withdifferent requirements of temperature, pressure, and flow must be served.This is generally the case when hospitals, laundries, airports, and kitchenshave to be supplied from the same distribution system. In those cases,separate circulation pumps are used for each zone, which permits independentregulation of the flow, pressure, and temperature for each group of relatedconsumers. The zone temperature is controlled by an individual temperaturecontrol valve through the blending connection for the zone. This permitsmaintaining a constant supply temperature to each zone of a distributionsystem and at the same time holding a constant expansion tank pressure. Thenet result is higher economy and flexibility.4-8

Cold water:

Cooling Water Systems

There are several types of cooling water systems utilized today in the engineering and design of power generation, petrochemical, and industrial plants. The most common system in use for many years in power generation was the direct use of the water from the nearby river, bay, or ocean. In this system a water intake structure is located along the shoreline and includes as a minimum circulating water pump(s), piping, both fixed and traveling intake screens, and the necessary crane facilities for the removal, replacement, and maintenance of the pumps and their motors. The intake screens are provided to prevent fish, crabs, and other debris from entering and damaging the pumps. In addition to this main cooling water system, there may be one or more service water systems for other equipment throughout the plant. The following guidelines apply in the design and routing of these systems:

● Where butterfly valves are used, follow the guidelines provided for valves. Any given heat exchanger inlet and outlet valves should be located close together for balancing the system.

● Avoid unnecessary vertical loops in any closed cooling water system. This type of system will usually include an expansion tank, which should be located at or above the highest point in the system, and the outlet from this tank should be piped directly to the pump suction.

● For piping at centrifugal pumps, follow the guidelines provided for piping of centrifugal pumps.

● Consult the Hydraulic Institute standards and the pump manufacturer's guidelines for layout and arrangement of deep-well type of pumps. Since the temperature in these systems is not high and does not vary widely, piping offsets to accommodate thermal expansion and/or contraction are not of paramount importance.

Fire Protection

The fire protection system usually consists of two or more fire pumps taking suction from the fire water source with the discharge of each pump independently connected to the underground fire main and as widely separated as possible. The underground fire main loop shall completely encircle the plant and may serve multiple sites if cross-connected between units. The National Fire Protection Association codes and the following guidelines may be used to design and lay out the yard fire main loop:

● Locate the yard fire main such that all fire hydrants will be a minimum of 50 ft (15 m) from any building or structure whenever possible.

● The underground fire main shall be sectionalized in accordance with NFPA code using post indicator valves.

● Post indicator valves shall be provided on each side of any fire pump discharge connection into the fire main loop.

● All fire protection system branches from the yard fire main loop shall be provided with a shutoff valve located not less than 40 ft (12 m) from the building or structure being served.

● Two-way fire hydrants with individual curb boxes should be provided at 250- to 300-ft (75- to 90-m) intervals along the yard fire main loop.

Water fire-extinguishing systems within any building may consist of automatic sprinkler systems, spray systems, deluge systems, and hose stations, as determined by the project engineering group. The following guidelines shall apply to the design of these systems:

● Large areas, such as below the turbine operating floor, should be divided into sectors each served by an individual branch from the yard fire main loop.

● Each sector should be controlled by an exterior post indicator valve and an alarm check valve or automatic valve located inside the building.

● The maximum area served by any one alarm check valve or automatic sprinkler valve shall not exceed 25,000 ft2 (7620 m2).

● The maximum number of sprinkler heads in any sector shall not exceed 275.

● Provide automatic wet sprinkler systems in the area of the tube oil system below the turbine operating floor and in the ceiling of the clean and dirty tube oil storage tank room.

● Separate water spray systems should be provided in the area of the tube oil system, in addition to the wet sprinkler system noted above, and in the area of the hydrogen seal system.

● Standpipes and hose stations should be provided in accordance with the NFPA code as a complement to the automatic suppression systems noted above.

● The hose stations on any given floor should be fed from above to avoid creating a series of unvented high points.

UTILITY MARKING TAPE:A. Utility marking tape shall be acid and alkali-resistant polyethylene film 6 inches wide withminimum thickness of 0.004 inch. Tape shall have a minimum strength of 1750 psilengthwise and 1500 psi crosswise. The tape shall be manufactured with integral wires, foilbacking, or other means to enable detection by a metal detector when the tape is buried upto 3 feet deep. The tape shall be of a type specifically manufactured for marking andlocating underground utilities. The metallic core of the tape shall be encased in a protectivejacket or provided with other means to protect it from corrosion. Tape color shall be asspecified in TABLE 1 and shall bear a continuous printed inscription (black lettering)describing the specific utility.TABLE 1Utility Color Printed InscriptionChilled Water Purple “Caution Chilled WaterLines -Do Not Drink”Communications Orange “Caution CommunicationLines”Potable Water Blue “Caution Water Lines Below”Gas Yellow “Caution Gas Lines”Electric Red “Caution Electric Lines”Sanitary Sewer Green “Caution Sanitary Sewer”Storm Sewer Green “Caution Storm Sewer”Fire Service Blue “Caution Fire Service”

Utility layout:

11. UTILITY LAYOUT AND SPACING

11.1 Requirements and Design Criteria

11.1.1 The utility area should be near the process area.

11.1.2 The utility area should be arranged for easy access and adequate working area provided around all equipment, for maintenance.

11.1.3 The cooling tower should be located to provide the least possible restriction to the free flow of air, and away from areas where drift or fogging might create a problem.

NFPA Code, Standard and Recommendation 214, Chapters 2 and 5 shall be considered for locating and spacing of cooling towers.

11.1.4 The circulating fuel oil system that supplies oil for process heaters and boilers is usually located in one corner of the utility area including tanks and circulating pumps. Tanks are to be diked.

11.1.5 All boilers are grouped together with space provided for at least one future boiler. All boiler auxiliaries including deaerator, feed pumps, flash drums and chemical feed systems are located in close proximity to the boiler. Consideration must be given to single stacks for each boiler or one common stack.

11.1.6 Plant and instrument air compressors including dryers should be located in the utility area.

11.1.7 Switchgear for the electrical system is placed in an enclosed building and located within the utility area. Substation serving process Units and offsite facilities are usually located in OGP process areas dependent upon the areas served.

11.1.8 Utility control house shall be provided to house all board mounted instruments used for operation and control of utility equipment.

11.1.9 Raw water storage and fire pumps shall be located adjacent to either the boilers or the cooling towers whichever provides the more economic arrangement.

11.1.10 Critical steam and power facilities feeding major portions of the plant shall be protected from possible fire or explosion in equipment handling hydrocarbons.

11.1.11 WASTE TREATMENT FACILITIES

1 The preferred location of the waste treatment area should be at a refinery/plant low point to insure gravity flow from all areas. Where this is not possible lift stations must be provided as required.

2 The waste treatment area should be remote from the process and utility area and arranged to permit future expansion of the system.

3 Layout of the area must include vehicle accessibility for maintenance purposes.

11.2 Spacing

General recommendation for spacing of boilers, utility & electric generating equipment, control houses, etc.,shall be as specified in Appendix A, Tables A-4, A-5, and A-6 .

(pdf utility layout and equip layout)

4. Electricity / Communication / Gas :GASThe primary uses of gas include heating, cooling (rarely used), and powering engines for electric generators. Gas pressures range from 20 psi to 50 psi in most utility distribution systems. When the gas enters the service connection, the pressure is typically reduced by a regulator to approximately l/4 to 1/2 psi. Since gas is a vapor it has a tendency to rise; this fact explains how such a low pressure can be used for distribution throughout a building. 

Pipe materials :

-Pipe made from mild steel, Grades A and B (specified minimum yield strengthsup to 35,000 psi in API)-Black steel pipe, coated to reduce corrosion, is the most commonly used gas distribution piping inside a building.

-Ductile-Iron. Ductile-iron pipe must be manufactured in accordance with ANSIA21.51/AWWA C151 Ductile Iron Pipe, Centrifugally Cast, in Metal Molds orSand Lined Molds for Gas.-Plastic. Plastic pipe and components must be manufactured in accordance withthe following American Society for Testing and Materials (ASTM) standards:ASTM D 2513 Thermoplastic Gas Pressure Pipe, Tubing,and FittingsASTM D 2517 Reinforced Epoxy Resin Gas PressurePipe and Fittings-Copper. Copper tubing or pipe for use in gas mains is limited to pressures of 100psi (7 kg/cm2) or less, must have a minimum wall thickness of 0.065 in (1.65 mm),and must be hard-drawn.Where the gas being transported contains more than an average of 0.3 grainsof hydrogen sulfide per 100 standard cubic feet (2.83 standard cubic meters) of gas,

copper may not be used.

ELECTRICAL/TELEPHONE/CABLE TV

The method of installation of underground electric, telephone, and cable TV are often very similar. All three

utilities have utilized both of the following installation methods:

1. Direct burial cable

2. Underground conduit (cable pulled through later)

In either case the trench depth will be dictated by the local utility as will the cable size and type. Direct burial cable is usually a simple and economic installation. There

are some strong advantages, though, to underground conduit. Firstly additional cable can be pulled at a later date by installing a spare conduit. Secondly the conduit

provides some protection from cable damage due to accidental excavation. Thirdly, some cable has a long delivery lead time and conduit installation allows the

remainder of the sitework to progress.