Chilled Water PipingChilled Water Piping

J.ILANGUMARANJ.ILANGUMARAN

Chilled Water PipingChilled Water Piping

�� The following organizations in the United States issue codes The following organizations in the United States issue codes and standards for piping systems and componentsand standards for piping systems and components

�� ASME ASME —— American Society of Mechanical EngineersAmerican Society of Mechanical Engineers

�� ASTM ASTM —— American Society for Testing and MaterialsAmerican Society for Testing and Materials

�� NFPA NFPA —— National Fire Protection AssociationNational Fire Protection Association

�� BOCA BOCA —— Building Officials and Code Administrators, Building Officials and Code Administrators, InternationalInternational

�� MSS MSS —— Manufacturers Standardization Society of the Manufacturers Standardization Society of the Valve and Fittings Industry, Inc.Valve and Fittings Industry, Inc.

�� AWWA AWWA —— American Water Works AssociationAmerican Water Works Association

Steel PipeSteel Pipe

�� Steel pipe is manufactured with wall thick Steel pipe is manufactured with wall thick nesses identified by schedule and weight. nesses identified by schedule and weight. Although schedule numbers and weight Although schedule numbers and weight designations are related, they are not constant designations are related, they are not constant for all pipe sizes.for all pipe sizes.

�� Standard weight (STD) and Schedule 40 pipe Standard weight (STD) and Schedule 40 pipe have the same wall thickness through 10 in. have the same wall thickness through 10 in. NPS. For 12 in. and larger standard weight pipe, NPS. For 12 in. and larger standard weight pipe, the wall thickness remains constant at 0.375 the wall thickness remains constant at 0.375 in., while Schedule 40 wall thickness increases in., while Schedule 40 wall thickness increases with each size. with each size.

�� A similar equality exists between Extra Strong A similar equality exists between Extra Strong (XS) and Schedule 80 pipe through 8 in.; above 8 (XS) and Schedule 80 pipe through 8 in.; above 8 in., XS pipe has a 0.500 in. wall, while Schedule in., XS pipe has a 0.500 in. wall, while Schedule 80 increases in wall thickness80 increases in wall thickness. .

Steel PipeSteel Pipe

�� Joints in steel pipe are made by welding or Joints in steel pipe are made by welding or

by using threaded, flanged, grooved, or by using threaded, flanged, grooved, or

welded outlet fittings. Unreinforced welded outlet fittings. Unreinforced

weldedwelded--in branch connections weaken a in branch connections weaken a

main pipeline, and added reinforcement is main pipeline, and added reinforcement is

necessary, unless the excess wall necessary, unless the excess wall

thickness of both mains and branches is thickness of both mains and branches is sufficient to sustain the pressure.sufficient to sustain the pressure.

Copper TubeCopper Tube

�� Because of their inherent resistance to corrosion Because of their inherent resistance to corrosion and ease of installation, copper and copper alloys and ease of installation, copper and copper alloys are often used in heating, airare often used in heating, air--conditioning, conditioning, refrigeration, and water supply installations.refrigeration, and water supply installations.

�� There are two principal classes of copper tube. There are two principal classes of copper tube. ASTM Standard B88 includes Types K, L, M, and ASTM Standard B88 includes Types K, L, M, and DWV for water and drain service. ASTM Standard DWV for water and drain service. ASTM Standard B280 specifies airB280 specifies air--conditioning and refrigeration conditioning and refrigeration (ACR) tube for refrigeration service.(ACR) tube for refrigeration service.

Copper TubeCopper Tube

�� Types K, L, M, and DWV designate descending wall thick Types K, L, M, and DWV designate descending wall thick

nesses for copper tube. All types have the same outside nesses for copper tube. All types have the same outside

diameter for corresponding sizes. diameter for corresponding sizes.

�� Usually Tables are used to know the properties of ASTM B88 Usually Tables are used to know the properties of ASTM B88

copper tube. In the plumbing industry, tube of nominal size copper tube. In the plumbing industry, tube of nominal size

approximates the inside diameter. approximates the inside diameter.

�� The heating and refrigeration trades specify copper tube by The heating and refrigeration trades specify copper tube by

the outside diameter (OD). ACR tubing has a different set of the outside diameter (OD). ACR tubing has a different set of

wall thick nesses.wall thick nesses.

�� Types K, L, and M tube may be hard drawn or annealed Types K, L, and M tube may be hard drawn or annealed (soft) temper.(soft) temper.

Copper TubeCopper Tube

�� The heating and airThe heating and air--conditioning industry conditioning industry

generally uses Types L and M tubing, which have generally uses Types L and M tubing, which have

higher internal working pressure ratings than the higher internal working pressure ratings than the

solder joints used at fittings. solder joints used at fittings.

�� Type K may be used with brazed joints for higher Type K may be used with brazed joints for higher

pressurepressure--temperature requirements or for direct temperature requirements or for direct

burial. burial.

�� Type M should be used with care where exposed Type M should be used with care where exposed

to potential external damageto potential external damage

Joining methodsJoining methods

�� Soldering and BrazingSoldering and Brazing

�� Flared and Compression JointsFlared and Compression Joints

�� FlangesFlanges

�� WeldingWelding

�� Steel pipe joints over 2 in. in diameter that have Steel pipe joints over 2 in. in diameter that have

been welded offer the following been welded offer the following

�� Other JointsOther Joints

�� Unions Unions

�� Plastic piping systemsPlastic piping systems

WATER PIPING SYSTEMWATER PIPING SYSTEMWATER PIPING SYSTEMWATER PIPING SYSTEMWATER PIPING SYSTEMWATER PIPING SYSTEMWATER PIPING SYSTEMWATER PIPING SYSTEM

Open SystemOpen System

��In this system, the water flows thru heat In this system, the water flows thru heat

exchanger and then exposed to atmosphere. exchanger and then exposed to atmosphere.

��such as in Cooling tower and air washer.such as in Cooling tower and air washer.

Closed systemClosed systemClosed systemClosed systemClosed systemClosed systemClosed systemClosed system

��In this system, the water flow is not exposed to In this system, the water flow is not exposed to

the atmosphere at any point.the atmosphere at any point.

��But some times contains an expansion tank that But some times contains an expansion tank that

is open to the atmosphere but water area is open to the atmosphere but water area

exposed is insignificant. Such as Chilled water exposed is insignificant. Such as Chilled water

systemsystem

Closed Water Piping SystemClosed Water Piping System

��Parallel Piping System Parallel Piping System Parallel Piping System Parallel Piping System Parallel Piping System Parallel Piping System Parallel Piping System Parallel Piping System

��Reverse return pipingReverse return piping

��Reverse return header with direct return Reverse return header with direct return

risersrisers

��Direct return pipingDirect return piping

��Compound Piping system Compound Piping system Compound Piping system Compound Piping system Compound Piping system Compound Piping system Compound Piping system Compound Piping system

(Primary & Secondary System)(Primary & Secondary System)(Primary & Secondary System)(Primary & Secondary System)(Primary & Secondary System)(Primary & Secondary System)(Primary & Secondary System)(Primary & Secondary System)

Reverse Return PipingReverse Return Piping

Reverse Return Headers with Reverse Return Headers with

Direct Return RisersDirect Return Risers

Direct Return Water PipingDirect Return Water Piping

Primary & Secondary PipingPrimary & Secondary Piping

FRICTION LOSSESFRICTION LOSSES

When water flows in a pipe, friction is When water flows in a pipe, friction is

produced by the rubbing of water particles produced by the rubbing of water particles

against each other and against the wall of against each other and against the wall of

the pipe. This friction produced by the the pipe. This friction produced by the

flowing water causes a loss in pressure, flowing water causes a loss in pressure,

which is called Friction Loss.which is called Friction Loss.

The Friction losses depends uponThe Friction losses depends upon::::::::

��Water velocityWater velocity

��Interior surface roughnessInterior surface roughness

��Pipe lengthPipe length

��Pipe diameterPipe diameter

Flow Rate LimitationFlow Rate Limitation

��ServicesServices

��ErosionErosion

��NoiseNoise

��Installation CostInstallation Cost

��Operating CostOperating Cost

All above limit Maximum and All above limit Maximum and

minimum velocities in piping minimum velocities in piping

system.system.

Recommended Water Recommended Water

Velocities Velocities Based on ServicesBased on Services

��Pump DischargePump Discharge 88--12 FPS 12 FPS

��Pump SuctionPump Suction 44--7 FPS7 FPS

��HeaderHeader 44--15 FPS15 FPS

��RiserRiser 33--10 FPS10 FPS

��Drain LineDrain Line 44--7 FPS7 FPS

��General ServiceGeneral Service 55--10 FPS10 FPS

��City WaterCity Water 33--7 FPS7 FPS

ErosionErosionErosionErosionErosionErosionErosionErosion

��Erosion in water piping system is Erosion in water piping system is the impingement on inside surface the impingement on inside surface of pipe of rapidly moving water of pipe of rapidly moving water containing air bubbles, sand and containing air bubbles, sand and other solid matter.other solid matter.

��Due to this impingement, pipes Due to this impingement, pipes gets eroded over a period of time gets eroded over a period of time if if Recommended velocity not Recommended velocity not maintained in piping systems.maintained in piping systems.

MAXIMUM WATER VELOCITY TO MAXIMUM WATER VELOCITY TO MAXIMUM WATER VELOCITY TO MAXIMUM WATER VELOCITY TO MAXIMUM WATER VELOCITY TO MAXIMUM WATER VELOCITY TO MAXIMUM WATER VELOCITY TO MAXIMUM WATER VELOCITY TO

MINIMIZE EROSIONMINIMIZE EROSIONMINIMIZE EROSIONMINIMIZE EROSIONMINIMIZE EROSIONMINIMIZE EROSIONMINIMIZE EROSIONMINIMIZE EROSION

Normal OperationNormal Operation Velocity RangeVelocity Range

��1500 Hrs/Year1500 Hrs/Year 15 FPS15 FPS

��2000 2000 ““ 14 FPS14 FPS

��3000 3000 ““ 13 FPS13 FPS

��4000 4000 ““ 12 FPS12 FPS

��6000 6000 ““ 10 FPS10 FPS

��8000 8000 ““ 8 FPS8 FPS

Noise GenerationNoise Generation

VelocityVelocity--dependent noise in piping systems dependent noise in piping systems results from any or all of four sources: results from any or all of four sources:

��TurbulenceTurbulence

��CavitationCavitation

��Release of entrained airRelease of entrained air

��Water hammerWater hammer

In investigations of flowIn investigations of flow--related Noise, Marseille, related Noise, Marseille,

Ball and Webster and Rogers reported that Ball and Webster and Rogers reported that

velocities on the order of velocities on the order of 10 to 1710 to 17 fps lie within the fps lie within the

range of allowable noise levels for residential and range of allowable noise levels for residential and

commercial buildings.commercial buildings.

Ashrae Recommendations Ashrae Recommendations Ashrae Recommendations Ashrae Recommendations Ashrae Recommendations Ashrae Recommendations Ashrae Recommendations Ashrae Recommendations For For

Hydronic SystemHydronic System

��Friction Loss Rate should be taken as Friction Loss Rate should be taken as 1 to 1 to

44 Feet/100 feet of Pipe Feet/100 feet of Pipe Eq.LengthEq.Length. .

��A Value of A Value of 2.5 Feet/1002.5 Feet/100 Feet is the mean Feet is the mean

to which most systems are designed.to which most systems are designed.

��For 2 Inch and below pipes, Velocity limit For 2 Inch and below pipes, Velocity limit

is is 4 FPS.4 FPS.

��For above pipes, For above pipes, FLR limit is FLR limit is 4 Feet/1004 Feet/100

Feet.Feet.

AndAnd

��As per Carrier Guide Line FLR is 8As per Carrier Guide Line FLR is 8--10 feet /100 10 feet /100

feet and velocity limit 10 FPS. feet and velocity limit 10 FPS.

PIPE SIZING CRITERIAPIPE SIZING CRITERIAPIPE SIZING CRITERIAPIPE SIZING CRITERIAPIPE SIZING CRITERIAPIPE SIZING CRITERIAPIPE SIZING CRITERIAPIPE SIZING CRITERIA

��Water Flow Water Flow

��Based on Cooling load on respective AHU Based on Cooling load on respective AHU

/FCU/BCU/FCU/BCU

��Can be calculated as:Can be calculated as:

Tonnage X 24Tonnage X 24

Flow In GPM= Flow In GPM= ------------------------------------------------------------------Temperature differenceTemperature difference

��Friction Loss Rate / Velocity LimitationFriction Loss Rate / Velocity Limitation

specified by consultant or ASHRAE.specified by consultant or ASHRAE.

Pipe Sizing MethodPipe Sizing MethodPipe Sizing MethodPipe Sizing MethodPipe Sizing MethodPipe Sizing MethodPipe Sizing MethodPipe Sizing Method

Step Step --11

��Make a layout sketch showing individual Make a layout sketch showing individual

AHU,FCU and BCU on Master layout plan.AHU,FCU and BCU on Master layout plan.

Step Step -- 22

��Mark selected /design flow on individual AHU, Mark selected /design flow on individual AHU,

FCU and BCU.FCU and BCU.

Step Step -- 33

��Review layout sketch w.r.t. space available , Review layout sketch w.r.t. space available ,

other services,economy and consultant other services,economy and consultant

concurrence.concurrence.

��Conclude layout.Conclude layout.

Pipe Sizing MethodPipe Sizing MethodPipe Sizing MethodPipe Sizing MethodPipe Sizing MethodPipe Sizing MethodPipe Sizing MethodPipe Sizing Method…………………………………………................

Step Step --44

��Starting from most remote terminal working Starting from most remote terminal working towards the pump, Mark the Cumulative flow in towards the pump, Mark the Cumulative flow in mains and branch circuits.mains and branch circuits.

Step Step --66

��Select pipe size for required Flow and as per Select pipe size for required Flow and as per selected Friction Loss Rate from Friction chart selected Friction Loss Rate from Friction chart for respective application.for respective application.

��ReRe--check Chart water velocity with check Chart water velocity with recommended velocity.recommended velocity. If within limit.Selection If within limit.Selection is ok.is ok.

��Repeat for other flow requirements.Repeat for other flow requirements.

Friction Loss Rate Vs Flow Charts Friction Loss Rate Vs Flow Charts --SchSch. 40 pipes. 40 pipes

Head Loss & CalculationHead Loss & Calculation

It is the total loss of pressure energy due to It is the total loss of pressure energy due to

friction/resistance offered by Pipes & Fittings friction/resistance offered by Pipes & Fittings

in the piping systemin the piping system

TThe he Head LossHead Loss is equal to the is equal to the Total Total

Frictional LossesFrictional Losses in highest resistant in highest resistant

circuit of piping system.circuit of piping system.

��To Calculate Head Loss, Calculate the Total To Calculate Head Loss, Calculate the Total

Frictional Losses Frictional Losses

��of pipesof pipes

��of fittingsof fittings

��of equipmentsof equipments

Valve & Fitting LossesValve & Fitting Losses

��Valves & Fitting cause pressure losses greater than Valves & Fitting cause pressure losses greater than those caused by the pipe alone.those caused by the pipe alone.

��Fitting Losses are frequently expressed in Equivalent Fitting Losses are frequently expressed in Equivalent length of pipe, length of pipe,

�� It can be expressed as per following equationIt can be expressed as per following equation

��������h = K x Vh = K x V22//2g2g����������hh-- Head/Pressure loss in FeetHead/Pressure loss in Feet

��KK -- Geometry & Size dependent loss coefficientGeometry & Size dependent loss coefficient

��VV -- Average velocity of waterAverage velocity of water

��gg -- Gravitational force as 32.20Gravitational force as 32.20

K FactorsK Factors--Screwed FittingsScrewed Fittings

K FactorsK Factors--Flanged FittingsFlanged Fittings

Fitting Losses in Equivalent Length of Fitting Losses in Equivalent Length of

PipePipe

Valves Losses in Valves Losses in EqEq. Length of . Length of

PipesPipes

System Friction LossesSystem Friction LossesSystem Friction LossesSystem Friction LossesSystem Friction LossesSystem Friction LossesSystem Friction LossesSystem Friction Losses

Relation between Relation between Flow & Head Losses Flow & Head Losses for a systemfor a system: :

1.85 1.85 1.85 1.85 1.85 1.85 1.85 1.85 --------1.91.91.91.91.91.91.91.9

H2/H1 = (Q2/Q1)H2/H1 = (Q2/Q1)H2/H1 = (Q2/Q1)H2/H1 = (Q2/Q1)H2/H1 = (Q2/Q1)H2/H1 = (Q2/Q1)H2/H1 = (Q2/Q1)H2/H1 = (Q2/Q1)

Q1& Q2 = FlowsQ1& Q2 = FlowsQ1& Q2 = FlowsQ1& Q2 = FlowsQ1& Q2 = FlowsQ1& Q2 = FlowsQ1& Q2 = FlowsQ1& Q2 = Flows

H1 & H2=Head LossesH1 & H2=Head LossesH1 & H2=Head LossesH1 & H2=Head LossesH1 & H2=Head LossesH1 & H2=Head LossesH1 & H2=Head LossesH1 & H2=Head Losses

Water Piping DiversityWater Piping Diversity

When the air conditioning load is determined for When the air conditioning load is determined for each exposure of a building, it is assumed that the each exposure of a building, it is assumed that the exposure is at peak load. Since the sun load is at a exposure is at peak load. Since the sun load is at a maximum on one exposure at a time, not all of the maximum on one exposure at a time, not all of the units on all the exposures require maximum water units on all the exposures require maximum water flow at the same time to handle the cooling load. flow at the same time to handle the cooling load. Units on the same exposure normally require Units on the same exposure normally require maximum flow at the same time; units on the maximum flow at the same time; units on the adjoining or opposite exposures do not. adjoining or opposite exposures do not. Therefore, Therefore, if the individual units are automatically controlled if the individual units are automatically controlled to vary the water quantity, the system water to vary the water quantity, the system water quantity actually required during normal operation quantity actually required during normal operation is less than the total water quantity required for is less than the total water quantity required for the peak design conditions for all the exposuresthe peak design conditions for all the exposures..

Diversity ApplicationDiversity Application

�� The principle of diversity allows the The principle of diversity allows the engineer to evaluate and calculate engineer to evaluate and calculate the reduced water quantity. the reduced water quantity.

�� For applying diversity two For applying diversity two conditions must be satisfied:conditions must be satisfied:

�� The water flow to the units must he The water flow to the units must he automatically controlled to compensate automatically controlled to compensate for varying loads.for varying loads.

�� Diversity may only be applied to piping Diversity may only be applied to piping that supplies units on more than one that supplies units on more than one exposure.exposure.