9.2.1. Pre-commissioning

A pre-commissioning program includes but is not limited to the following tasks that the operator should check them before startup of the CCHP system. It is recommended to use the operation manuals provided by the manufacturers, as these manuals are the main source of O&M information. A more professional method is to provide a checklist of actions that should be completed before startup and follow the checklist for each pre-commissioning of the CCHP system.

1. Always follow the safety procedures and use safety equipment such as proper boots, clothing, gloves, goggles, etc.

2. Make sure that no tag-out/lockout is applied to equipment such as motors, valves, etc.

3. Make sure that all of the electrical connections are safe and correct (check for correct grounding, check electrical insulation for uncovered wires, connection to the grid, correct direction of rotation of the electrical motors used for driving pumps, fans, and other rotary equipment, etc.).

4. Check the lubrication system (check the oil level in the oil reservoir, look for oil leakage in the oil piping, connections, and components that are supposed to be lubricated, make sure that the oil recommended by the manufacturer is used, make sure that the oil filters are not clogged, make sure that the oil coolers can operate properly, if oil is water cooled make sure water is there and look for water leakage and if it is air cooled make sure that fans are installed correctly, if some components are lubricated by grease check that the grease meets standards and is sufficient and clean).

5. Make sure that all the mechanical connections are well connected. (look for loose-fitting, misaligned couplings, belts, and pipe connections, avoid incorrect positioning of valves, etc.)

6. Check the fuel, the fuel pressure, and temperature requirements.

7. Check the sealing system and its auxiliary subsystems (pump flushing line, gas sealing lines of compressor and gas turbine, oil seal line, steam sealing line, etc.).

8. Check the cooling systems (jacketing of engines, motors, bearings, lube oil cooling, etc.).

9. Check all of the filters and strainers for clogging or failure (air intake filters of gas turbines and compressors, lubrication system filters, suction pump strainer, fuel filters, etc.).

10. Look for closed inlet air baffles that provide enough fresh air for combustion in the prime mover, boiler, etc.

11. Make sure that all of the measurement instrumentation is calibrated and that the calibration date has not expired.

12. Check the condition of thermal insulation used for hot or cold lines, TES systems, etc. Never press the insulation; this reduces the thickness and as a result the thermal resistance decreases and energy loss increases.

13. If the CCHP system has a liquid-type solar collector, make sure it is protected from freezing in a cold climate. Also make sure it is placed in the optimum direction to receive maximum solar heat.

14. Check the hot and cold connections to heat exchangers and make sure they are not connected incorrectly. In the shell and tube exchangers water flows on the tube side most of the time, because fouling cleaning on the tube side is much easier than on the shell side.

9.2.2. Commissioning

After pre-commissioning of the CCHP system, startup is the next step. The commissioning in general includes but is not limited to the following steps. Make sure that the pre-commissioning steps are completed correctly and completely.

1. Inform your supervisor and other colleagues about the commissioning.

2. Run the lubrication system correctly. The lubrication system is the first system that should be run during startup because most of the component wear happens due to incorrect startup. The lubrication system usually includes a reservoir, oil heater, strainer, main and auxiliary pump, recirculation pump, main and auxiliary filter, main and auxiliary cooler, pressure gages, thermometer level controls, etc. Check the oil temperature; usually the best temperature for lubrication oil is about 40°C. If the oil temperature is low, start the oil heater and circulation pump to increase the oil temperature homogeneously. Prime the auxiliary components of the lubrication system by starting the auxiliary pump. Priming includes venting, filling with oil, and making the components ready for use in standby. After priming, follow the manufacturer recommended steps to run the main pump to start lubrication. If the lube oil pump is a positive displacement type (reciprocating, gear, screw, etc.) make sure that the discharge valve is open to avoid extreme pressure that may cause damage to the components. If the pump is centrifugal, the discharge valve should be closed at the startup and opened slowly and gradually; in this step the min flow line should stay open until the discharge valve is fully open.

3. Bring the cooling systems into operation. The cooling systems may include the air cooler or cooling tower and heat exchangers. The cooling towers have a fan and pump, but air coolers usually have two fans. This rotary equipment should be run according to the manufacturer guidelines. Always check the water quality, scale formation in the heat exchangers, and the cooling tower’s fill packing.

4. Bring the sealing systems into operation. Running the prime mover, pumps, and other rotary equipment before running the sealing systems can cause serious damage to the sealing systems and other components. Make sure that enough flow with proper pressure will be used in the flushing and sealing systems.

5. Bring the heat recovery heat exchangers into operation. In the heat exchangers the cold fluid should flow first into the heat exchanger and then the hot fluid. Hot and cold lines should be opened gradually to avoid thermal stress in the exchanger.

6. If cooling is required, the auxiliary systems of the cooling system should be operated. For absorption chillers the refrigerant and solution pumps, vacuum pump, cooling tower pumps, cooling water pump, chilled water pump, etc. should be operated. At this stage the auxiliary systems use grid electricity for operation. When the prime mover is operated, the auxiliary systems can use the CCHP electricity and become disconnected from the grid. The compression chillers use electricity, therefore they can stay offline until the CCHP can provide enough electricity to use the cooling system. It is very important to follow the manufacturer instructions for the startup of the cooling systems.

7. Run the prime mover. The startup procedure of prime mover very much depends on the prime mover type. The procedure recommended by the manufacturer must be followed to run the prime mover safely and correctly.

8. The auxiliary boiler starts working automatically whenever needed. But it should be ready for operation.

9. If the CCHP system has a solar collector, the solar systems enter into operation to use solar heat when the sun is shining.

10. If the CCHP system has a TES system, bring it online so it can charge.

11. If the CCHP system uses electricity storage systems, bring them online to store surplus electricity for selling or using during electrical peak hours.

9.2.3. Post-commissioning

After startup or commissioning of the CCHP system, the operator still has very important duties. Some of these tasks should be done just after the commissioning and others should be done at certain times when the CCHP system is operating. The following procedure can be considered a guideline, but the operators should be aware that these guidelines are general; they may need to revise and extend them for their own CCHP system and its components.

General routine checks in the first hour after commissioning are recommended as below; the operator may need to check some of these items several times in the first hour of operation to confirm the safe operation of the system.

1. Make sure that all the commissioning steps are taken correctly and completely. It is more convenient to provide a checklist for this purpose and tick the commissioning procedure step by step.

2. Listen for cavitation noise in the pumps. It sounds like small sand particles circulating inside the pump.

3. Check the bearings temperature. An unusually hot bearing is a sign of bearing failure, wrong oil type, oil pollution, oil corruption, shaft misalignment, excessive vibration, shaft run out, mass unbalance, etc.

4. Check for excessive vibration in the bearings, casings, and couplings. Vibration may be due to misalignment, bearing damage, shaft run out, cavitation, mass unbalance, etc.

5. Check for sudden shaking in the piping, fittings, and valves that may be a sign of water hammering.

6. Check for any type of leakage in the heat exchangers, lube oil systems, hot and cold pipelines, etc. Check the permissible leakage of packing-type pump sealing systems. Packing-type sealing systems need cooling. If water is used for to cool the packing, 60 droplets of water per minute is required for proper cooling. Less leakage results in packing overheating and burning and finally excessive leakage. Leakage of more than 60 droplets per minute may be due to a loose gland, packing failure, and incorrect placement of packing rings and lantern rings in the stuffing box.

7. Check that the amperage of electrical motors is in range. High amperage is a sign of improper operation or overloading of rotary equipment connected to the motor.

8. Check the pressure gages for fluctuating pressure at the pump discharges. Fluctuating pressure may be due to cavitation, impeller failure, etc.

9. Check the pumps for fluctuating flow rate. Fluctuation in the pump flow rate may be due to cavitation, impeller failure, low level fluid in the fluid source (cooling tower basin, oil reservoir, etc.).

10. Check the oil temperature and pressure before entering the bearings.

11. Check that the cooling water flow and temperature is in the correct range.

12. Check the differential pressure of the filters and strainers.

13. Check the oil temperature and pressure before and after lubrication.

14. Check the differential pressure (DP) of heat exchangers; high DP is a sign of excessive scale formation and fouling in the heat exchangers.

15. Check that the min flow line of pumps is closed to avoid wasting of energy.

16. Check that all the measurement instruments are working and none of them is stuck or stopped.

17. Check all of the fans, and their coupling and motors. Listen for unusual noise.

18. Check the cooling tower for excessive drift and for any nozzles that may not be working; also check the PH and hardness of water.

19. Check the electrical, heating, and cooling terminals of the consumer and make sure they receive the required energy type with the best quality.

20. Make sure that you have checked all the tasks given to you in the checklists for equipment. When you are certain about pre-commissioning, commissioning, and post-commissioning procedures you can plan your next visit to the CCHP system equipment to check the operating log sheets.

9.2.4. Operating Log Sheets

After completing the pre-commissioning, commissioning, and post-commissioning checklists a successful operator follows up on the operation of the CCHP cycle to avoid the development of technical problems. Recognizing a problem when it starts to show up lets us fix the problem before it develops and become a bigger problem that may cause an unscheduled shutdown or emergency.

Operation log sheets contain some parameters that should be read or checked by the operators from the control system or measurement instruments. Usually a permissible variation range is defined for parameters such as pressure, temperature, vibration, etc. Continuous records of these parameters can reveal the trend of parameters (i.e., if they are steadily increasing, steadily decreasing, fluctuating, or steadily constant). These trends help us to recognize what parameters are going to make trouble in the CCHP system and its components. Therefore, in addition to reading the correct data from the CCHP components, analyzing the log sheets is the most important task of the operator and supervisor in recognizing the problems before development of potential cause emergencies.

Here three simple but different examples are presented to show that detecting them as they start gives us the opportunity to repair them at the right time without paying extra costs or causing an unscheduled shutdown.

Example 1: The suction strainer of a pump is clogged.

A DP increase through the pump’s suction strainer can be solved easily by cleaning the strainer; this is what a successful operator does. However, if the pressure drop across the suction strainer increases further it can result in low-pressure cavitation in the pump suction eye. Cavitation erodes the internal parts of the pump; generates noise and vibration; makes the discharge pressure and flow fluctuate; increases the axial and radial forces, thus overheating and damaging bearings; increases the oil temperature; and also creates problems for the sealing system. As can be seen timely recognition of the problem and repairing it promptly avoids all the negative consequences.

Example 2: The water level in the cooling tower is decreasing.

Decreasing water level in the basin of a cooling tower can be simply recognized using the recorded data on the log sheets of the cooling tower. A successful operator is one who undertakes prompt action to increase the water level to avoid the hazardous effects of low water level, and at the same time starts a troubleshooting procedure to find the main reason for water loss in the system to remove the problem completely.

It should be mentioned that accurate troubleshooting avoids repetition of the same trouble in the CCHP cycle. For example, prompt action to increase the water level in the cooling tower in this example is an introductory action to avoid further damage, but if we do not find the main reason for the water loss, the water consumption of the cooling tower increases steadily, which is unfavorable. A favorable action is to remove the main reason for water loss in the system, and at the same time doing prompt actions to avoid damage in the CCHP components due to low water level in the cooling tower.

Example 3: Water flow of heat recovery systems at constant load is increasing.

Increasing water flow rate of a heat recovery system can be easily recognized according to the recordings in the log sheets. Extra water flow means higher pump energy consumption. Over the long term, the pumping cost increases significantly. In addition, in the design step, pumps are selected based on the best efficiency point (BEP) operation. This means that the pump is chosen to operate as close as possible to the operating point with the highest efficiency. When the flow rate has changed significantly, the operation point would be displaced and moves away from the pump BEP. In this condition the loss of pumping energy due to low efficiency operation of the pump will be added to the costs of a high flow rate in the heat recovery system.

Operators always should look for the easy explanations first. This means the reasons that do not require any shut down or disassembling of equipment from the CCHP system.

Increased flow rate may be due to leakage in the pump sealing, piping, or exchangers; installation of new consumer terminals such as fan coils; uncalibrated flow measurement instruments; increased heat loss energy from the prime mover due to increasing water jacketing, oil cooler, or exhaust temperatures, etc.

As can be seen, an increase in the water flow rate for heat recovery can occur for a span of reasons that ranges from easy to difficult. The troubleshooter and operator should categorize the reasons from simple to difficult and investigate the solutions in that order. If solving a problem requires shutdown or disassembling equipment it should be done only with written permission from the supervisor, owner, and consumers of the CCHP system. To investigate the trouble and conduct the troubleshooting in as effective a manner as possible, a guideline is presented below.

9.2.5. Troubleshooting

Successful troubleshooters can save significant maintenance and part replacement costs. They analyze the log sheet data and operator reports to find trouble points. They find the main reason for problems and propose possible solutions while avoiding any extra maintenance jobs that may result in extra cost and cause other problems for the components.

A general procedure for troubleshooting of equipment is proposed in the following:

1. First of all define the problem clearly. What exactly is the problem? What is the expected situation? What is the current condition? And what was the previous situation?

2. Find out about the history of the equipment. How long it has been working? When was the last overhaul of the CCHP system and its components? What changes have been made to the CCHP system and its components? In comparison with the previous overhauls were there repetitive changes and part replacement? When did the current problem start? Was it just after overhaul or after a long period of operation after the overhaul? How has the problem developed? Was it quick or gradual? Look for trends of different parameters, such as temperature, pressure, flow rate, vibration, etc. Are these parameters constant, steadily increasing, steadily decreasing, or fluctuating? Is the problem increasing, decreasing, fluctuating, or constant?

3. Verification. Make sure that all of the readings are correct. Make sure that the calibration date has not expired. Make sure that no measurement instrument is broken or stuck or has stopped working.

4. Requirements for troubleshooting. Everything that may assist you for troubleshooting should be available including operation log sheets; pre-commissioning, commissioning, and post-commissioning checklists; P&I diagrams; cross-section drawings of equipment; operation instructions from the manufacturer; operator reports; reports of previous overhaul and maintenance jobs; and last recoded data from the equipment.

5. Make a list of reasons that may cause the current problem in the CCHP system and categorize them from simple to hard according to cost, maintenance job, shutdown requirement, equipment disassembly, etc.

6. Apply for maintenance after you have informed your supervisor, CCHP owner, and consumers.

As a sample, in the following some general troubles that may occur in the equipment are analyzed.

Example 4: The lubrication oil temperature has increased.

Possible reasons, corrective actions, and recognition method:

1. Incorrect oil type is possibly used; check the certificates of the recommended oil and compare it with the newly used oil.

2. Oil is foaming excessively due to losing its anti-foam additives, or water and air leakage into the oil system. Oil analysis can be done to find out about it. Water leakage into the oil can be tested by getting sample oil from the drain valve of the oil reservoir. Excessive foam can be pumped into the lubrication system. As a result not enough oil will be used for lubrication and oil temperature increases rapidly. Excessive foam can even create fire in hot areas especially those in contact with some flammable insulation.

3. Oil is polluted due to oxidation, ambient pollution such dust particles, etc. This pollution decreases the lubrication properties of oil and the oil temperature increases accordingly. Oil analyses can reveal the pollution type.

4. If the oil cooler is a water-type exchanger, it may have been fouled and the cooling process may not have been conducted properly. This can be recognized by looking at the oil temperature difference variation and water pressure drop change across the oil cooler. In this case the power consumption of the electromotor increases as well.

5. If there is a water-type oil cooler, the water temperature has possibly increased due to incorrect operation of the cooling tower. If this is the reason, the cooling tower must be analyzed to find the main reason for its incorrect operation. For example, it may be due to loss of pump capacity, excessive drift, insufficient make-up water, fouling in the fill packing, improper distribution of water by the tower’s nozzles, etc. It should be noted that if the loss of pump capacity is the main reason, it should be analyzed as well

6. If there is an air-cooled oil cooler, the fans are probably off or not working properly. Visit the fans and check to find out.

7. If an air-cooled oil cooler is used, the elevated ambient air temperature can decrease the cooler efficiency and increase the oil temperature. Check the ambient temperature. If it is high, you can increase the fan speed or use water spray between the exchanger and fans as auxiliary evaporative cooling during hot times of the day.

8. Failure of bearings. Failure of a bearing also creates noise and vibration. Therefore it can be recognized based on the noise or vibration. If a bearing has failed, corrective actions must be taken as soon as possible because it can produce serious problems for other parts as well. For example the vibration due to bearing damage may cause damage to the sealing system with very narrow clearances, hazardous vibration for rigid couplings, wearing of labyrinth and wearing rings, etc.

9. Misalignment in the couplings or bearings. Misalignment generates vibration in the bearings and couplings as well.

10. Oil filters have clogged. Due to clogging the filters, less oil flows to the bearings and as a result the oil becomes hotter. This can be recognized according the pressure drop across the filters.

11. The oil heater inside the reservoir is working while it should be off. Check if the heater is on or off.

12. Thermometer is out of calibration. Check the oil temperature with a portable thermometer in the oil reservoir.

13. Other possible causes.

After listing the possible reasons, classify them into 3 classes of “only small change or adjustment is required, no shutdown, no disassembling,” “shutdown is required, no disassembling is needed,” and “shutdown and disassembling are required” and check the reasons from the first class to the third class.

Example 5: Chilled water temperature from the absorption chiller to the fan coils has increased.

1. Heat source energy is insufficient. If the chiller is indirect fire, the heat source temperature, pressure, or its flow rate has probably decreased and vaporization of the refrigerant in the generator has decreased accordingly. Check the flow rate, temperature, and pressure of the heat source entering the generator.

2. Heat source is not sufficient. If the chiller is direct fire there may be insufficient fuel or oxygen for completing the combustion process. Check the inlet air baffle positions and fuel pressure.

3. Vacuum inside the evaporator is broken. The vacuum pump has probably failed or the chiller has air leaking from ambient to the chiller. Check the vacuum pump operation, and use leakage discovery methods.

4. The temperature of return water from the cooling tower is high. High temperature water from the cooling tower is a problem for the condenser and absorber of the chiller. This can be easily checked by using thermometers to check the return water temperature. This problem can occur due to scale formation on the fill packing or in the spray nozzle, improper working of the tower fan, etc.

5. The flow rate of water to the condenser is low. To find out about this problem you can check the pump discharge valve position, check for cavitation, check the water level in the tower basin, and check the pump suction strainer for clogging,

6. Cooling load has increased. This can be checked by looking at the outdoor temperature and return water temperature from the terminal consumers. This may happen due to newly installed terminal consumers, increase in outdoor temperature, etc.

7. Cold line insulation have been removed, cut, scratched, or compressed. Check the insulation for any deformation or removal.

8. The thermometer is not calibrated. Check the calibration of the thermometer.

9. Refrigerant pump is leaking and the refrigerant level in the chiller has decreased. Check the refrigerant pump for leakage from the sealing system, connections, and flanges.

10. The condenser tubes are fouled from the inside. Check the amperage of pump’s electromotor. Increase in the electromotor amperes is a sign of increasing friction head loss of the pump. In addition you can check the hardness and PH of water in the cooling tower. PH higher than 7.5 can increase scale formation rapidly, while PH smaller than 6.5 increases chemical corrosion.

More information about the operation and maintenance of CCHP equipment can be found in the manufacturer documents and [1–5].