Chilled Water Piping
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Chilled Water Piping
J.ILANGUMARAN
Chilled Water Piping The following organizations in the United States issue codes and standards for piping systems and components ASME — American Society of Mechanical Engineers ASTM — American Society for Testing and Materials NFPA — National Fire Protection Association BOCA — Building Officials and Code Administrators, International MSS — Manufacturers Standardization Society of the Valve and Fittings Industry, Inc. AWWA — American Water Works Association
Steel Pipe Steel pipe is manufactured with wall thick nesses identified by schedule and weight. Although schedule numbers and weight designations are related, they are not constant for all pipe sizes. Standard weight (STD) and Schedule 40 pipe have the same wall thickness through 10 in. NPS. For 12 in. and larger standard weight pipe, the wall thickness remains constant at 0.375 in., while Schedule 40 wall thickness increases with each size. A similar equality exists between Extra Strong (XS) and Schedule 80 pipe through 8 in.; above 8 in., XS pipe has a 0.500 in. wall, while Schedule 80 increases in wall thickness.
Steel Pipe Joints in steel pipe are made by welding or by using threaded, flanged, grooved, or welded outlet fittings. Unreinforced welded-in branch connections weaken a main pipeline, and added reinforcement is necessary, unless the excess wall thickness of both mains and branches is sufficient to sustain the pressure.
Copper Tube Because of their inherent resistance to corrosion and ease of installation, copper and copper alloys are often used in heating, air-conditioning, refrigeration, and water supply installations. There are two principal classes of copper tube. ASTM Standard B88 includes Types K, L, M, and DWV for water and drain service. ASTM Standard B280 specifies air-conditioning and refrigeration (ACR) tube for refrigeration service.
Copper Tube Types K, L, M, and DWV designate descending wall thick nesses for copper tube. All types have the same outside diameter for corresponding sizes. Usually Tables are used to know the properties of ASTM B88 copper tube. In the plumbing industry, tube of nominal size approximates the inside diameter. The heating and refrigeration trades specify copper tube by the outside diameter (OD). ACR tubing has a different set of wall thick nesses. Types K, L, and M tube may be hard drawn or annealed (soft) temper.
Copper Tube The heating and air-conditioning industry generally uses Types L and M tubing, which have higher internal working pressure ratings than the solder joints used at fittings. Type K may be used with brazed joints for higher pressure-temperature requirements or for direct burial. Type M should be used with care where exposed to potential external damage
Joining methods
Soldering and Brazing Flared and Compression Joints Flanges Welding Steel pipe joints over 2 in. in diameter that have been welded offer the following Other Joints Unions Plastic piping systems
WATER PIPING SYSTEM Open System In this system, the water flows thru heat exchanger and then exposed to atmosphere. such as in Cooling tower and air washer.
Closed system In this system, the water flow is not exposed to the atmosphere at any point. But some times contains an expansion tank that is open to the atmosphere but water area exposed is insignificant. Such as Chilled water system
Closed Water Piping System Parallel Piping System Reverse return piping Reverse return header with direct return risers Direct return piping
Compound Piping system (Primary & Secondary System)
Reverse Return Piping
Reverse Return Headers with Direct Return Risers
Direct Return Water Piping
Primary & Secondary Piping
FRICTION LOSSES When water flows in a pipe, friction is produced by the rubbing of water particles against each other and against the wall of the pipe. This friction produced by the flowing water causes a loss in pressure, which is called Friction Loss. The Friction losses depends upon: Water velocity Interior surface roughness Pipe length Pipe diameter
Flow Rate Limitation Services Erosion Noise Installation Cost Operating Cost All above limit Maximum and minimum velocities in piping system.
Recommended Water Velocities Based on Services Pump Discharge
8-12 FPS
Pump Suction
4-7 FPS
Header
4-15 FPS
Riser
3-10 FPS
Drain Line
4-7 FPS
General Service
5-10 FPS
City Water
3-7 FPS
Erosion Erosion in water piping system is the impingement on inside surface of pipe of rapidly moving water containing air bubbles, sand and other solid matter. Due to this impingement, pipes gets eroded over a period of time if Recommended velocity not maintained in piping systems.
MAXIMUM WATER VELOCITY TO MINIMIZE EROSION Normal Operation
Velocity Range
1500 Hrs/Year
15 FPS
2000 “
14 FPS
3000 “
13 FPS
4000 “
12 FPS
6000 “
10 FPS
8000 “
8 FPS
Noise Generation Velocity-dependent noise in piping systems results from any or all of four sources: Turbulence Cavitation Release of entrained air Water hammer
In investigations of flow-related Noise, Marseille, Ball and Webster and Rogers reported that velocities on the order of 10 to 17 fps lie within the range of allowable noise levels for residential and commercial buildings.
Ashrae Recommendations For Hydronic System Friction Loss Rate should be taken as 1 to
4 Feet/100 feet of Pipe Eq.Length. A Value of 2.5 Feet/100 Feet is the mean to which most systems are designed. For 2 Inch and below pipes, Velocity limit is 4 FPS. For above pipes, FLR limit is 4 Feet/100 Feet. And As per Carrier Guide Line FLR is 8-10 feet /100 feet and velocity limit 10 FPS.
PIPE SIZING CRITERIA Water Flow Based on Cooling load on respective AHU /FCU/BCU Can be calculated as: Tonnage X 24 Flow In GPM= --------------------------------Temperature difference
Friction Loss Rate / Velocity Limitation specified by consultant or ASHRAE.
Pipe Sizing Method Step -1 Make a layout sketch showing individual AHU,FCU and BCU on Master layout plan.
Step - 2 Mark selected /design flow on individual AHU, FCU and BCU.
Step - 3 Review layout sketch w.r.t. space available , other services,economy and consultant concurrence. Conclude layout.
Pipe Sizing Method…….. Step -4 Starting from most remote terminal working towards the pump, Mark the Cumulative flow in mains and branch circuits.
Step -6 Select pipe size for required Flow and as per selected Friction Loss Rate from Friction chart for respective application. Re-check Chart water velocity with recommended velocity. If within limit.Selection is ok. Repeat
for other flow requirements.
Friction Loss Rate Vs Flow Charts -
Sch. 40 pipes
Head Loss & Calculation It is the total loss of pressure energy due to friction/resistance offered by Pipes & Fittings in the piping system The Head Loss is equal to the Total Frictional Losses in highest resistant circuit of piping system. To Calculate Head Loss, Calculate the Total Frictional Losses of pipes of fittings of equipments
Valve & Fitting Losses Valves & Fitting cause pressure losses greater than those caused by the pipe alone. Fitting Losses are frequently expressed in Equivalent length of pipe, It can be expressed as per following equation h = K x V2/2g h- Head/Pressure loss in Feet K - Geometry & Size dependent loss coefficient V - Average velocity of water g - Gravitational force as 32.20
K Factors-Screwed Fittings
K Factors-Flanged Fittings
Fitting Losses in Equivalent Length of Pipe
Valves Losses in Eq. Length of Pipes
System Friction Losses Relation between Flow & Head Losses for a system: 1.85 -1.9 H2/H1 = (Q2/Q1) Q1& Q2 = Flows H1 & H2=Head Losses
Water Piping Diversity When the air conditioning load is determined for each exposure of a building, it is assumed that the exposure is at peak load. Since the sun load is at a maximum on one exposure at a time, not all of the units on all the exposures require maximum water flow at the same time to handle the cooling load. Units on the same exposure normally require maximum flow at the same time; units on the adjoining or opposite exposures do not. Therefore, if the individual units are automatically controlled to vary the water quantity, the system water quantity actually required during normal operation is less than the total water quantity required for the peak design conditions for all the exposures.
Diversity Application The principle of diversity allows the
engineer to evaluate and calculate the reduced water quantity. For applying diversity two conditions must be satisfied: The water flow to the units must he
automatically controlled to compensate for varying loads. Diversity may only be applied to piping that supplies units on more than one exposure.
J.ILANGUMARAN
Chilled Water Piping The following organizations in the United States issue codes and standards for piping systems and components ASME — American Society of Mechanical Engineers ASTM — American Society for Testing and Materials NFPA — National Fire Protection Association BOCA — Building Officials and Code Administrators, International MSS — Manufacturers Standardization Society of the Valve and Fittings Industry, Inc. AWWA — American Water Works Association
Steel Pipe Steel pipe is manufactured with wall thick nesses identified by schedule and weight. Although schedule numbers and weight designations are related, they are not constant for all pipe sizes. Standard weight (STD) and Schedule 40 pipe have the same wall thickness through 10 in. NPS. For 12 in. and larger standard weight pipe, the wall thickness remains constant at 0.375 in., while Schedule 40 wall thickness increases with each size. A similar equality exists between Extra Strong (XS) and Schedule 80 pipe through 8 in.; above 8 in., XS pipe has a 0.500 in. wall, while Schedule 80 increases in wall thickness.
Steel Pipe Joints in steel pipe are made by welding or by using threaded, flanged, grooved, or welded outlet fittings. Unreinforced welded-in branch connections weaken a main pipeline, and added reinforcement is necessary, unless the excess wall thickness of both mains and branches is sufficient to sustain the pressure.
Copper Tube Because of their inherent resistance to corrosion and ease of installation, copper and copper alloys are often used in heating, air-conditioning, refrigeration, and water supply installations. There are two principal classes of copper tube. ASTM Standard B88 includes Types K, L, M, and DWV for water and drain service. ASTM Standard B280 specifies air-conditioning and refrigeration (ACR) tube for refrigeration service.
Copper Tube Types K, L, M, and DWV designate descending wall thick nesses for copper tube. All types have the same outside diameter for corresponding sizes. Usually Tables are used to know the properties of ASTM B88 copper tube. In the plumbing industry, tube of nominal size approximates the inside diameter. The heating and refrigeration trades specify copper tube by the outside diameter (OD). ACR tubing has a different set of wall thick nesses. Types K, L, and M tube may be hard drawn or annealed (soft) temper.
Copper Tube The heating and air-conditioning industry generally uses Types L and M tubing, which have higher internal working pressure ratings than the solder joints used at fittings. Type K may be used with brazed joints for higher pressure-temperature requirements or for direct burial. Type M should be used with care where exposed to potential external damage
Joining methods
Soldering and Brazing Flared and Compression Joints Flanges Welding Steel pipe joints over 2 in. in diameter that have been welded offer the following Other Joints Unions Plastic piping systems
WATER PIPING SYSTEM Open System In this system, the water flows thru heat exchanger and then exposed to atmosphere. such as in Cooling tower and air washer.
Closed system In this system, the water flow is not exposed to the atmosphere at any point. But some times contains an expansion tank that is open to the atmosphere but water area exposed is insignificant. Such as Chilled water system
Closed Water Piping System Parallel Piping System Reverse return piping Reverse return header with direct return risers Direct return piping
Compound Piping system (Primary & Secondary System)
Reverse Return Piping
Reverse Return Headers with Direct Return Risers
Direct Return Water Piping
Primary & Secondary Piping
FRICTION LOSSES When water flows in a pipe, friction is produced by the rubbing of water particles against each other and against the wall of the pipe. This friction produced by the flowing water causes a loss in pressure, which is called Friction Loss. The Friction losses depends upon: Water velocity Interior surface roughness Pipe length Pipe diameter
Flow Rate Limitation Services Erosion Noise Installation Cost Operating Cost All above limit Maximum and minimum velocities in piping system.
Recommended Water Velocities Based on Services Pump Discharge
8-12 FPS
Pump Suction
4-7 FPS
Header
4-15 FPS
Riser
3-10 FPS
Drain Line
4-7 FPS
General Service
5-10 FPS
City Water
3-7 FPS
Erosion Erosion in water piping system is the impingement on inside surface of pipe of rapidly moving water containing air bubbles, sand and other solid matter. Due to this impingement, pipes gets eroded over a period of time if Recommended velocity not maintained in piping systems.
MAXIMUM WATER VELOCITY TO MINIMIZE EROSION Normal Operation
Velocity Range
1500 Hrs/Year
15 FPS
2000 “
14 FPS
3000 “
13 FPS
4000 “
12 FPS
6000 “
10 FPS
8000 “
8 FPS
Noise Generation Velocity-dependent noise in piping systems results from any or all of four sources: Turbulence Cavitation Release of entrained air Water hammer
In investigations of flow-related Noise, Marseille, Ball and Webster and Rogers reported that velocities on the order of 10 to 17 fps lie within the range of allowable noise levels for residential and commercial buildings.
Ashrae Recommendations For Hydronic System Friction Loss Rate should be taken as 1 to
4 Feet/100 feet of Pipe Eq.Length. A Value of 2.5 Feet/100 Feet is the mean to which most systems are designed. For 2 Inch and below pipes, Velocity limit is 4 FPS. For above pipes, FLR limit is 4 Feet/100 Feet. And As per Carrier Guide Line FLR is 8-10 feet /100 feet and velocity limit 10 FPS.
PIPE SIZING CRITERIA Water Flow Based on Cooling load on respective AHU /FCU/BCU Can be calculated as: Tonnage X 24 Flow In GPM= --------------------------------Temperature difference
Friction Loss Rate / Velocity Limitation specified by consultant or ASHRAE.
Pipe Sizing Method Step -1 Make a layout sketch showing individual AHU,FCU and BCU on Master layout plan.
Step - 2 Mark selected /design flow on individual AHU, FCU and BCU.
Step - 3 Review layout sketch w.r.t. space available , other services,economy and consultant concurrence. Conclude layout.
Pipe Sizing Method…….. Step -4 Starting from most remote terminal working towards the pump, Mark the Cumulative flow in mains and branch circuits.
Step -6 Select pipe size for required Flow and as per selected Friction Loss Rate from Friction chart for respective application. Re-check Chart water velocity with recommended velocity. If within limit.Selection is ok. Repeat
for other flow requirements.
Friction Loss Rate Vs Flow Charts -
Sch. 40 pipes
Head Loss & Calculation It is the total loss of pressure energy due to friction/resistance offered by Pipes & Fittings in the piping system The Head Loss is equal to the Total Frictional Losses in highest resistant circuit of piping system. To Calculate Head Loss, Calculate the Total Frictional Losses of pipes of fittings of equipments
Valve & Fitting Losses Valves & Fitting cause pressure losses greater than those caused by the pipe alone. Fitting Losses are frequently expressed in Equivalent length of pipe, It can be expressed as per following equation h = K x V2/2g h- Head/Pressure loss in Feet K - Geometry & Size dependent loss coefficient V - Average velocity of water g - Gravitational force as 32.20
K Factors-Screwed Fittings
K Factors-Flanged Fittings
Fitting Losses in Equivalent Length of Pipe
Valves Losses in Eq. Length of Pipes
System Friction Losses Relation between Flow & Head Losses for a system: 1.85 -1.9 H2/H1 = (Q2/Q1) Q1& Q2 = Flows H1 & H2=Head Losses
Water Piping Diversity When the air conditioning load is determined for each exposure of a building, it is assumed that the exposure is at peak load. Since the sun load is at a maximum on one exposure at a time, not all of the units on all the exposures require maximum water flow at the same time to handle the cooling load. Units on the same exposure normally require maximum flow at the same time; units on the adjoining or opposite exposures do not. Therefore, if the individual units are automatically controlled to vary the water quantity, the system water quantity actually required during normal operation is less than the total water quantity required for the peak design conditions for all the exposures.
Diversity Application The principle of diversity allows the
engineer to evaluate and calculate the reduced water quantity. For applying diversity two conditions must be satisfied: The water flow to the units must he
automatically controlled to compensate for varying loads. Diversity may only be applied to piping that supplies units on more than one exposure.
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