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Chilled water pumps that are commonly used in HVAC industry are the centrifugal pumps. It basically consists of a pump impeller which is connected to the shaft of a motor. The centrifugal force created when the motor turns causes the liquid to be drawn towards it and discharged to the opening of the volute.
The pump create a differential pressure between the water inlet and outlet of the pump. This pressure differential enables the water to flow through the pipes.
The motor used can be single speed, dual speed or variable speed. The more complicated variable speed motor which can vary its speed and connected to the building management system is increasingly being used due to its better efficiency and control. By varying the speed of the pump motor, the impeller speed can be optimized to the load of the system.
The moving parts of the pumps are usually made of bronze or other non-ferrous material to prevent corrosion. The body is made from cast-iron for stability and durability.
These pumps are used in:
In-Line Pumps and the Closed Coupled Pump
There are two main design of the chilled water pumps. They are the In-Line Pumps and the Closed Coupled Pump.
The in-line type is smaller which is used for a lower head applications. It is also known as booster pumps. The suction and discharge are connected in a straight line making it light in weight and hence can be supported directly by the piping. It is also less costly and simpler to install.
The closed coupled pump has its impeller mounted on and supported by the motor shaft. It has mounting flange with base that supports the motor and pump. There is also an end suction connection. It is available from small to medium capacities and is not too costly.
Blade Angle
The design of the blade has different effect on the Pump Head vs Discharge. If the design is forward-curved where the outlet blade angle > 90°, the positive slope is obtained. This positive condition is not stable and cause the pump to surge. The pump surge is a condition where it oscillates to find the proper operating point. Due to this, this design is seldom used.
If the design is backward-curved where the outlet blade angle < 90°, the negative slope is obtained. This is the most stable pump characteristics and hence is the most preferred design in centrifugal pumps.
In the design and installation consideration of chilled water pumps, it is always a good practice to provide for venting air from the system to prevent air from blocking the proper operation of the fluid flow. Efficiency of the pump will be reduced with the introduction of air in the piping system.
When selecting pump, choose one with 60-80% of the maximum flow as it is not advisable to operate at its maximum capacity. This is to cater for the sudden increase in flow when extra capacity is needed.
For more info contact ebara pump suppliers in uae or call us at +971 4 252 2966
The pump create a differential pressure between the water inlet and outlet of the pump. This pressure differential enables the water to flow through the pipes.
The motor used can be single speed, dual speed or variable speed. The more complicated variable speed motor which can vary its speed and connected to the building management system is increasingly being used due to its better efficiency and control. By varying the speed of the pump motor, the impeller speed can be optimized to the load of the system.
The moving parts of the pumps are usually made of bronze or other non-ferrous material to prevent corrosion. The body is made from cast-iron for stability and durability.
These pumps are used in:
- Condenser water system where the hot water from the condenser is pumped to the cooling tower which is located a distance away from the condenser. The hot water is then cooled at the cooling tower before being circulated back to the condenser. This process is done repeatedly.
- Chilled water system where the chilled water from the chillers are being pumped and circulated to the various sections of a building before being used to cooled the space.
- Hot water system where the hot water from the boiler is circulated to the heat transfer units and back.
In-Line Pumps and the Closed Coupled Pump
There are two main design of the chilled water pumps. They are the In-Line Pumps and the Closed Coupled Pump.
The in-line type is smaller which is used for a lower head applications. It is also known as booster pumps. The suction and discharge are connected in a straight line making it light in weight and hence can be supported directly by the piping. It is also less costly and simpler to install.
The closed coupled pump has its impeller mounted on and supported by the motor shaft. It has mounting flange with base that supports the motor and pump. There is also an end suction connection. It is available from small to medium capacities and is not too costly.
Blade Angle
The design of the blade has different effect on the Pump Head vs Discharge. If the design is forward-curved where the outlet blade angle > 90°, the positive slope is obtained. This positive condition is not stable and cause the pump to surge. The pump surge is a condition where it oscillates to find the proper operating point. Due to this, this design is seldom used.
If the design is backward-curved where the outlet blade angle < 90°, the negative slope is obtained. This is the most stable pump characteristics and hence is the most preferred design in centrifugal pumps.
In the design and installation consideration of chilled water pumps, it is always a good practice to provide for venting air from the system to prevent air from blocking the proper operation of the fluid flow. Efficiency of the pump will be reduced with the introduction of air in the piping system.
When selecting pump, choose one with 60-80% of the maximum flow as it is not advisable to operate at its maximum capacity. This is to cater for the sudden increase in flow when extra capacity is needed.
For more info contact ebara pump suppliers in uae or call us at +971 4 252 2966
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Purchasing the best pump in the world for your HVAC or chilled water system could be done, if it is installed improperly, additional costs in replacement parts, labor expenses and equipment down time. If you want to keep commercial chilled water pumps running for the long haul, you need to insure that best practices are followed, starting with the initial installation.
- Don’t add additional stress to your pumps. Be sure to include flexible connectors to prevent external piping loads. Additionally, ensure that adjacent piping hangers are properly installed!
- Mechanical Seals. When seals go bad, it’s often due to other issues, the majority of which are caused by improper installation. First of all, be sure to select the correct seal for the application. Also, NEVER run the pump dry and never operate at a “dead head” (at shut-off condition) for more than a couple minutes. For flexible coupled pumps, ensure that the pump shaft is properly aligned during installation and again during startup.
- Most bearing failures are caused by misaligned pump shafts (have we stressed alignment enough yet?), excessive heat (usually from OVER-lubrication), and dirt or moisture contamination.
- Keep your balance. Base mounted end pumps must be properly aligned to maintain balance and decrease pump vibration. For other pumps, be sure that the impellers are appropriately balanced prior to startup. You don’t want that impeller wobbling around like a ceiling fan in the old saloon!
- Proper pressure gauge installation. A lot of people think that if one pressure gauge is good, then two is better. However, installing two gauges will not be accurate for pump performance. Install only one gauge according to the O&M manual.
- Install external seal flush lines. An external flush will keep damaging solids away from the seal, isolate the seal from pumped fluid, cool the seal and carry away seal generated heat. Adding a sediment separator on the seal flush line will also significantly boost the life expectancy of your mechanical seals.
- Bleed the air from the volute. Air has no business there.
- Drain pans. Always use drain pans for chilled water condensation and for all pumps to catch water any time you have to open up the volute. Piping the drain pan to a floor drain will help keep your mechanical room clean and safe from stray puddles!
- Protect the pump from foreign debris. Utilize a suction strainer or some other form of solid/sediment separator to clean your system and keep trash from ruining your impellers and mechanical seals. And don’t forget that suction diffusers have fine mesh temporary screens that should ALWAYS be removed after initial startup and system flush. Hang it on the inlet valve handle so everyone knows it’s done!
