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Evaporator Maintenance & Water Distribution Components Maintenance


Chiller Systems: Routine Maintenance: Chapter 3


Evaporator Maintenance


In this module, we will take a look at routine maintenance of the evaporator in the chiller system. Skip to quiz!


Introduction


Recall that chiller systems usually contain a shell and tube type of evaporator. Shell and tube evaporators consist of a bundle of copper tubes inside a large metal shell.


Chiller efficiency is greatly affected by the cleanliness of the evaporator tubes. Chiller efficiency declines rapidly if the evaporator tubes are not clean. After a period of time, the evaporator tubes become fouled with impurities picked up from the water system.


If evaporator maintenance is without correct methods and chemicals, it may damage the tubes. So, it is of most importance for the maintenance to be carried out by trained technicians.


We follow the same procedure as shell and tube condenser to clean shell and tube evaporator. This is because some water evaporates in the cooling tower, so scale forming minerals density increases. In the evaporator, the same water circulates for a long time. There will be no loss of water.


Most chiller manufacturers recommend cleaning the condenser tubes annually since they are typically part of an open system. They recommend cleaning evaporators tubes once every three years since they are part of a closed system.


For cleaning the shell and tube evaporator, we first turn off the power supply and shut off the evaporator inlet and outlet valves. We have to remove the front and back covers of the evaporator. Then we have to clean the evaporator tubes with the rodding machine.


We also clean the gasket surfaces. We replace the gaskets if they are damaged. Finally, we reassemble the evaporator and check its working.



Chiller efficiency declines rapidly if the evaporator tubes are not clean. If evaporator maintenance is without correct methods and chemicals, it may damage the tubes. They recommend cleaning evaporators tubes once every three years since they are part of a closed system.


 

Water Distribution Components Maintenance


In this module, we will take a look at routine maintenance of water distribution components in the chiller systems. Skip to quiz!


Introduction


Water pumps circulate cold water into a building. Centrifugal pumps are the most popular and commonly used for circulating water in chiller systems. Water pumps should be in good condition for the smooth running of chiller systems.


For performing the maintenance of the water pump, we first turn off the power supply. We check the stiffness of the water pump mountings. We have to tighten the nuts of the water pump if they are loose.


We check that all the electrical terminals of the water pump are tight. We have to check the pump and piping for leaks. We need to check for unusual vibration and excessive temperature during water pump maintenance.


When a centrifugal water pump overheats, it not only damages internal components but is also a hazard to technicians. It is important to ensure that pumps do not overheat.


We have to check the temperature of the pump with the hand by touching the outer casing. If it is overheated, we have to stop the pump immediately and let it cool. We need to rectify the problem before switching on the water pump.


Recall that vibration is simply a back and forth movement or oscillation of components in motorized equipment. Vibration in the water pump causes excessive noise. If we neglect vibration, it causes higher energy bills and even damage to the pump.


Major reasons for pump vibration are:

  • Damaged impeller,

  • Misalignment of shafts,

  • Water leakages, and

  • Weak foundation.

Let us look into how to resolve these problems of water pump vibration.


Recall that impeller is a component that rotates inside the casing of the centrifugal pump. Non-uniform wear or blade breakage of the impeller can increase the vibration in the pump. We have to replace the impeller if it is damaged.


We have to check the alignment of the pump with the motor. Misalignment of shafts is one of the key sources of vibration in centrifugal pumps.


Water leakages in the centrifugal pump due to deterioration of mechanical seals. Excessive pressure, temperature, or corrosion can loosen the seals, which allows water to leak. A seal is a device that is used to control leakage between a rotating shaft and a water filled vessel.


We have to tighten the fasteners around the joint to fix a leaking pump. If the water leakage from the pump does not fix by tightening the fasteners, we have to replace the seals.


The purpose of the foundation for a centrifugal pump is to help dampen the vibration. The foundation of a centrifugal pump should be capable of absorbing the vibration transmitted to it without shifting the pump’s position. Check the hold-down bolts for tightness and tighten if necessary.


We have to ensure that the pump’s foundation is flat with a spirit level. We have to check the hold-down bolts for tightness and tighten them if necessary.


Recall that lubrication is the action of applying oil or grease to the motor to minimize friction and allow smooth movement. Lubrication is one of the main factors that impact the pump’s operation. By lubricating moving parts such as bearings, we can minimize the friction that causes wear and tear.


We have to clean all the outer parts of the centrifugal pump with a brush and wipe them with a cloth. We also need to clean the surroundings of the water pump.



Strainer


A strainer is a pipe fitting used to filter the water flowing through a pipeline. Strainers have wire mesh inside them that traps dirt from the water. These protect piping equipment from potential damage caused by the dirt.


A clogged strainer creates a barrier for the water flow through it. It also increases the load on the water pump, thereby increasing the energy consumption. So we have to clean the strainer for smooth operation.


For cleaning the strainer, first, turn off the water pump and close the inlet and outlet valves. We remove the nuts of the strainer to remove the strainer cap. We then remove the mesh from the strainer and clean it with water. Finally, we have to reassemble the strainer and check for its proper working.



Valve


Recall that valves are a device used to decrease or stop the flow of a fluid. They’re a type of fitting that controls the flow inside the piping.


Some of the valves used in chiller systems are:

  • Ball valves,

  • Butterfly valves,

  • Gate valves,

  • Globe valves, and

  • Check valves.


Recall that lubrication is the action of applying oil or grease to the motor to minimize friction and allow smooth movement. Without lubrication, valve components wear out very fast. Lubricants reduce the friction between the moving parts of the valve. Let us see how to lubricate the ball valve with the grease gun.


For lubricating the ball valve, we have to connect the grease gun to the zerk fitting on the top of the ball valve. We then pump the grease by the handle of the grease gun.


We have to inspect for the water leakage in the valves. If there is any leakage of water, we have to tighten the nuts of the valve. If the leak is because of the failure of valve parts, we have to change the valve.



For performing the maintenance of the water pump, we first turn off the power supply. We remove the mesh from the strainer and clean it with water. A grease gun is used to lubricate the valves. If there is any leakage of water, we have to tighten the nuts of the valve.


 

Question #1: Which of the following components cleaning procedure is the same? (Select all that apply)

  1. Chiller evaporator

  2. Expansion valve

  3. Microchannel condenser

  4. Shell and tube condenser

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Answer: Chiller evaporator

Shell and tube condenser

We follow the same procedure as shell and tube condenser to clean shell and tube evaporator, but the frequency of cleaning is less.


Question #2: Which of the following two require frequent cleaning comparatively?

  1. Shell and tube evaporator

  2. Shell and tube condenser

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Answer: Shell and tube condenser

Shell and tube condenser requires frequent cleaning compared to shell and tube evaporator.


Question #3: A rodding machine is used to clean the ________.

  1. Chiller’s metering device

  2. Chiller’s evaporator tubes

  3. Chiller’s evaporator fins

  4. Chiller’s filter drier

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Answer: Chiller’s evaporator tubes

A rodding machine is used to clean the chiller’s evaporator tubes.


Question #4: Which of the following instrument is used to check the flatness of the centrifugal pump’s foundation?

  1. Spirit level

  2. Multimeter

  3. Magnehelic gauge

  4. Thermometer

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Answer: Spirit level

Spirit level is used to ensure that the flatness of the centrifugal pump’s foundation.


Question #5: Which of the following is the first action before starting the water pump maintenance?

  1. We have to remove the water pump end cap

  2. We have to turn off the power supply to the water pump

  3. We have to check the tightness of the electrical terminals

  4. We have to check the temperature of the water pump touching it

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Answer: We have to turn off the power supply to the water pump

For performing the maintenance of the water pump, we first turn off the power supply.


Question #6: Which of the following need to be done before cleaning the strainer? (Select all that apply)

  1. We have to apply coil cleaner and wait for ten minutes

  2. Water pump connected to the strainer should be switched off

  3. Inlet and outlet valves of the strainer should be in closed condition

  4. Water in the chilled water pipeline should be drained out

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Answer: Water pump connected to the strainer should be switched off

Inlet and outlet valves of the strainer should be in closed condition

For cleaning the strainer, first, turn off the water pump and close the inlet and outlet valves.


Question #7: Which of the following equipment is used to lubricate the valves?

  1. Thermometer

  2. Grease gun

  3. Manifold gauge

  4. Multimeter

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Answer: Grease gun

A grease gun is used to lubricate the valves.


Question #8: Which of the following action can stop the water leakage from the valve?

  1. Applying grease

  2. Tightening the nuts

  3. Lowering chiller water temperature

  4. Insulating the valve

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Answer: Tightening the nuts

We can stop the water leakage from the valve by tightening the valve nuts.



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