Transformation of the control system of the hottes

2022-08-18
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The total installed capacity of Shajiao C power plant is 3 × 660 MW。 The compressed air source system of the plant is equipped with four centrifugal air compressors and two sets of adsorption dryers, which are cooled by closed circulating cooling water

in recent years, due to the reasons of design, operation and maintenance, the failure rate of the air compressor system is high, and it has led to the shutdown accident of the unit. For this reason, the power plant has formulated and implemented a series of technical transformation schemes

1 improve the safety and reliability of the system

less moisture absorption

due to design and other reasons, there are some potential safety hazards in the air compressor system. For example, such a failure occurred once. Because the air compressor tripped, the pressure of the instrument compressed air tank after the dryer gradually decreased. After a period of time, the air compressor could be started normally, and the outlet pressure of the air compressor soon reached the set value, but the inspection found that the pressure of the air tank after the dryer was still declining. The inspection found that the two inlet pneumatic valves of the dryer were all closed, and the compressed air could not pass through. The reason is that the air source of the pneumatic valve cylinder at the inlet of the dryer originally designed is from the outlet pipeline of the dryer. When the system pressure drops to a certain extent, the torque provided by the pneumatic actuator cannot open the closed valve. Even after the air compressor runs, the compressed air cannot pass through the dryer, and the pneumatic valve at the inlet of the dryer cannot obtain the power source with sufficient pressure. To this end, take a gas source from the inlet header of the dryer, pass through a small filter, combine it with the original gas source, and supply it to the inlet pneumatic valve, so as to ensure that when the system pressure decreases, as long as the air compressor can operate, the dryer can work normally

other measures include: increasing the capacity of the high-level cooling water tank and installing water level monitoring instruments; Strengthen the management of the cleanliness and service life of the air compressor cooler; Operators conduct anti accident drills on a regular basis

2 reduce the failure rate of equipment

in daily maintenance, focus on tracking the equipment with high failure rate sponsored by China Plastics Processing Industry Association at this meeting, analyze the reasons, and then implement improvement. For example, there are many faults that the bypass valve of the air compressor cannot be closed, which greatly reduces the air supply volume and efficiency of the air compressor, and is easy to cause the instability of the system pressure. The main reasons are:

(1) the IP converter and pilot valve spool are polluted by water and rust, the air hole of the IP converter is blocked or the pilot valve spool is blocked, resulting in the failure of the valve. To this end, DSM, the air compressor instrument air supply main, increased the global production capacity of optical fiber and cable materials business (originally carbon steel pipe) and replaced it with 316 stainless steel pipe; And install a filter on the air compressor air source main pipe to improve the quality of air source for air compressor control

(2) controller output error. The air compressor used in Shajiao C power plant controls the opening of the bypass valve according to the motor current. When the ambient temperature is very high or the cooling effect of the air compressor cooler is not good, the density of compressed air is small, the motor output is small, the motor current will be low, and the controller will mistakenly recognize that the air flow is low. In order to prevent the machine from surging, the controller outputs a command to open the bypass valve to circulate the compressed air in the machine, so that the external air supply of the compressor is greatly reduced. Find out the root of the problem and take corresponding solutions: strengthen the monitoring of the closed cooling water system of the air compressor; Clean or replace the air cooler of the air compressor regularly; Clean the cooling tower regularly; Install water level instrument to monitor water level; Ensure the cooling effect of the air cooler. When the ambient temperature is very high or the machine performance drops, if the bypass valve still cannot be closed after taking the above measures, the lower current limit parameter can be modified, and the opening (closing) point of the bypass valve can be changed to make the air compressor bypass valve operate normally

in addition, the device is upgraded from the original MP3 controller to CMC controller. The new controller adds the control signal output indication of the inlet valve/bypass valve, which has higher reliability. In the use of single chip microcomputer, the working curve of the air compressor is optimized, so that the working efficiency of the air compressor is higher

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