What is the reason for the low ball collection rate of condenser rubber ball cleaning?

The basic task of rubber ball cleaning system is to ensure the normal circulation of rubber balls, so that rubber balls can be exported and recovered smoothly (the system is shown in figure 1). Due to system problems, the low ball collection rate will directly affect the cleaning effect of condenser.

The possible problems of rubber ball cleaning system are various, depending on the system structure and action mechanism. According to the modification of rubber ball cleaning system for previous unit overhaul, the rubber ball cleaning system of condenser in Yangpu Power Plant has the following problems: rubber ball circulating unit problem, ball catching screen problem, primary and secondary filter screen influence, operation influence, etc.

1. 1 rubber ball circulation unit problem

The rubber ball circulation unit consists of a ball collector, a rubber ball pump and corresponding pipes. The ball collector is a vertical cylindrical container with a glass window for observation on the top cover of the container. The ball collector has a built-in filter screen, which is driven by an electric actuator and can rotate to the rubber ball collection position or the rubber ball circulation position. Problems in operation of rubber ball circulating device;

(1) One side of rubber ball pump has serious fever.

(2) There is more air in circulating water, which leads to insufficient suction capacity of rubber ball pump.

(3) There is a shell in the ball receiver.

For the above problems, after comprehensive analysis, we found that the equipment foundation position is too compact, which is not conducive to equipment installation. At the same time, the installation unit did not install the equipment in strict accordance with the design drawings, and the commissioning and acceptance were not strict. Therefore, during the overhaul, the installation position of the rubber ball pump was moved from directly below the original turbine spindle to the inlet and outlet pipes of the condenser. In this way, the layout of the ball receiving pipeline is reasonable, the number of pipeline elbows is reduced, the pipeline is no longer bulky, the pipe fittings are reduced, the resistance loss along the pipeline is reduced, and the pressure difference between the two rubber ball pumps is roughly equal, thus solving the problem of heating of the pump body of a single rubber ball pump.

1.2 the problem of receiving network board

The ball receiving net consists of two net plates, which are of A-shaped structure, with the water facing end at the top, and completely block the whole pipeline section. The bottom of each sieve plate is provided with a rubber ball outlet through which the rubber ball is led out to the circulation unit. Each sieve plate is driven by a rotating shaft, which can rotate to a certain angle in the non-operating state, forming an H-shaped structure slightly inclined to the direction of water flow. At this time, the water flow backwashes the screen plate to remove impurities on the screen plate, and the screen plate changes back to an A-shaped structure during operation.

After opening the cover of the on-site catching net tube section, it can be seen that there is a big gap between the side plate of the catching net and the shell, and the shielding plate at the bottom of the net plate is deformed to some extent. In actual operation, due to the deformation or backwashing of the mesh plate, it can not be restored in place, the gap is too large, and the ball runs away. The transformation measures are as follows:

( 1)? By adding welding slats, the top clearance of the ball catching net plate and the clearance between the side plate and the shell are eliminated, and the ball escape is avoided. The bottom of the net plate has been deformed, and its structure has been properly reformed to strengthen its rigidity and make it cooperate well with the shell of the catch net.

(2)? The electronic actuator of the ball-collecting net adjusts the mechanical limit switch and the torque limit switch of the electronic actuator after the ball-collecting net plate is tightly closed, thus realizing the compression of the torque switch during the operation of the ball-collecting net plate, avoiding the vibration of the net plate under the impact of water flow, being beneficial to ball collection and prolonging the service life of the net plate. Similarly, when the screen plate is opened in the backwashing state, the negative influence caused by vibration can also be avoided by keeping the torque pressed on the limit pillar. Carve a line on the dial of the electronic actuator to indicate the correct opening and closing position of the net, so as to avoid the ball running because the net catching plate is not in place.

1.3? Influence of primary and secondary filter systems

At the beginning of the unit operation, due to frequent tripping and untimely detection of the chemical chlorine production device and the shutdown of the cathodic protection device after shutdown, the seawater system pipeline was seriously corroded, and there was sand hole leakage in the seawater outlet pipe section connecting the condenser. During the overhaul, the seawater pipeline was completely anticorrosion, the damaged primary and secondary filter screens were replaced, and the shell in the ball catcher was cleaned. Through the transformation of electrical circuit, the hidden trouble of chlorine production device tripping caused by the start-stop impact of seawater pump is completely solved, and the normal operation of chlorine production system is ensured. At the same time, reinstall the cathodic protection device.

1.4? Operational impact

Since the rubber ball cleaning system was put into operation, the phenomenon of unstable ball collection rate has appeared. Therefore, the Operation Technology Department stipulated that the operation procedures should be strictly implemented, the training of operation technical skills should be strengthened, the operation ability of operators should be improved, and a typical operation ticket was formulated. Before the rubber ball cleaning system is put into operation, the primary and secondary filter screens must be cleaned to ensure that impurities such as garbage will not block the pipeline, and the rubber ball should be put into operation after the pumps on both sides of the Taiwan Strait are turned on. When there is more air in the circulating water, resulting in insufficient suction capacity of the rubber ball pump, stop one rubber ball pump, close the main exit door, and use another pump to pour water to remove the air in the pipeline until there is no air bubble in the return pipe observation window, and then start the pump to throw rubber balls. The new rubber ball must be soaked for a specified time before being put into use, and the damaged and deformed rubber ball must be removed in time.

Second, the improvement effect and follow-up problems After several years of operation practice, it is proved that the measures we have taken are effective. The recovery rate of rubber ball cleaning system has been kept above 90%. Now it is not a time-consuming and laborious thing to put the rubber ball system into operation. Due to the normal operation of the rubber ball cleaning system, the high thermal efficiency and economy of the unit are ensured. While the transformation has achieved remarkable results, it is also recognized that improvements need to be made in the following two aspects:

1, install baffle to reduce the influence of turbulence at the outlet elbow of condenser;

2. Install deflector to eliminate dead angle of condenser water chamber and reduce spherical aberration rate.