chilled water piping system.pptx

7/27/2019 Chilled Water Piping System.pptx

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Prepared by

Chetan V Makwana


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Lets us first discuss What is a Pipe?

It is a Tubular item made of plastic, metal, etc used for

conveying liquids, gases or for that matter anything that flows.

It is further classified as Pipe & TubePipes are identified by NPS (Nominal Pipe Size ie; Inner

Diameter)

Tubes are identified by Outer Diameter (eg Copper tubes)


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What is Schedule of Pipe ?

Schedule is measure of internal pressure a pipe canwithstand without deflection or failure.

Standard Schedules of Pipes are 10, 40, 80, 120, etc. For eg

Schedule 40 pipe will be written as 40S where S stand for

Schedule. Sometimes 80X where X stands for extra strongpipe.

For a particular diameter of pipe, as the Schedule no

increases, its internal diameter decreases whereas Outer

Diameter remains constant.


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Chilled Water Pipe Material

Black Carbon Steel (ASTM A53 B, A106 B & API 5L)-generally

used for Chilled Water piping.

Stainless Steel (304/304L & 316/316L)-used where water

quality is poor or highly alkaline conditions exist. Copper Tubes (Type K,L,M)-hard/soft drawn copper tubes

with wall thickness decreasing from Type K (max wall

thickness) to Type M (least wall thickness).


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Manufacturing methods for Pipes

Seamless Pipe: It is manufactured by extruding the metal to the desired

length.

It can also be manufactured by Centrifugally pouring the

molten metal on the inside of the mould surface.

Thus seamless pipe does not have any joints in its cross

section through out its length.

Electric Resistance Welded Pipe:

It is manufactured by Rolling metal and then welded

longitudinally across its length.

Thus ERW Pipe has a welded joint in its cross section.


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Chilled Water Piping System

Once Thru System - here the water passes through the

equipment only once and is discharged.

Recirculation System - here the water is not discharged,but it continuously flows in a repeating circuit from

heat exchanger to equipment and back to heat

exchanger.


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Recirculating Systems are further classified as:

Open loop system It is the one in which water flows

into the reservoir open to atmosphere wherein the

Heat exchange occurs between the water and

atmosphere directly.

Closed loop system It is the one in which flow of

water is never exposed to the atmosphere at any point

during the heat exchange between pipe carrying water

and atmosphere.


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Recirculating systems are also classified wrt piping

arrangements as follows:

Direct Return piping (Refer fig 23)

Reverse Return Piping (Refer fig 21)

If Chilled water equipments have nearly the same

pressure drops then Reverse return method can be used.

However if units have different pressure drops then it is

more economical to use a Direct Return Piping method.


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Chilled Water Piping Design


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What is Friction?

Friction is the force resisting the relative motion of solidsurfaces, fluid layers etc against each other.

In the context of chilled water pipes, there is Frictional losswhich is loss of energy or head that occurs in pipe flowbetween the surfaces of pipe and layers of fluid.

This frictional loss depends upon the following factors:

1. Water velocity

2. Interior surface roughness

3. Pipe Diameter

4. Pipe LengthVarying any one of the above will influence the totalfrictional loss of pipe.


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Recommended Water Velocity for Chilled

Water Pipes:

Velocity (fps)

Pump Suction 4 to 7

Pump Discharge 8 to 12

Header 4 to 15

Riser 3 to 10


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Valves Accessories and AncillaryItems


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Ball Valve

Ball valves use a ball as the opening/closing mechanism to

control fluid flow.

The ball is rotated 90 degrees from full open to full closed;

therefore, it is well-suited for applications which require quickor frequent opening and closing. The ball seals by fitting

tightly against resilient seats located on each side of the ball.

Ball valves are generally selected for on/off service and are

most common in sizes 2 inches or less..


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Ball Valve


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Butterfly Valve

Butterfly valves in the chilled water system are most common

in the larger sizes due to the ease of operation, low cost, and

superior shutoff characteristics.

The butterfly valve usually consists of a wafer shaped bodywith a rotating disk that closes against a resilient seat located

within the valve body. Like the ball valve, a 90-degree rotation

of the operating mechanism results in valve travel from closed

to full open.

The butterfly valve is well-suited for on/off service.


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Butterfly Valve


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Globe Valve

Globe valves are primarily used for throttling service and are

not well-suited for full flow applications due to the high

resistance to flow designed into the valve.

The standard valve consists of a round disk or tapered plugthat seats against a round opening. Angle valves and needle

valves are variations of the standard globe valve and use a

similar method of closure.

Unlike the gate and ball valves, globe valves must be installed

in the proper direction of flow. Flow should enter through the

disk seat and push up against the valve disk. Reverse

installation will result in valve chatter, vibration, and

premature valve failure.


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Globe Valve


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Autoflow Balancing Valve

Autoflow balancing valve accurately and dynamically balances

the system with not more than +5% to -5% flow variation.

It reduces the manual work of adjusting the flow at each

terminal thereby reducing the time of Testing andCommissioning.

The valve is also fixed with Test ports to measure the flow,

pressure drop across the valve, etc.


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Autoflow Balancing Valve


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Non Return Valve/Check Valve

These are Unidirectional and allow flow of the fluid only

in a predetermined direction.

The most common application found is in the dischargepipeline of the pumps where there is more than onepump operating parallelly.


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Check Valve


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Y Strainer

Generally Y Strainers are installed in Chilled Water Supply line

of Equipments (AHU, FCU, Pump Suction) to remove debris,

foreign particles and to restrict them from entering the

Equipment Coil etc.

Pressure Guages are sometimes installed before and after

Strainer to keep a check on clogging of mesh.

Y strainers are sometimes provided with AutoBlow Valve

which helps in easy maintenance of strainer.


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Y Strainer


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Suction Diffuser

Suction Diffuser mounts either on vertical or horizontal

position which acts as an elbow, sometimes reducing elbow.

Also acts as strainer by removing hazardous material from

liquid before it enters into pump.

Suction Diffusers can be installed wherever there is space

constraint due to its ease of maintenance.


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Suction Diffuser


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Air Separator with & without Strainer

Due to the tangentially mounted connections, the water

inside the air separator is brought into rotation. The rotation

forces the heavy medium (water) against the wall of the air

separator while air is collected in the middle.

The collected air rises to the top and gets vented to the

outside by the float vent.

Impurities heavier than water, such as sand, welding debris

and the like are forced to settle down at the bottom


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Air Separator

chilled water piping system.pptx

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