Turbine overhaul is a systematic and meticulous work. High quality overhaul work is the premise and guarantee of normal and safe operation of turbine speed limit device. Therefore, in the process of overhaul, it is necessary to improve the quality and efficiency of overhaul while ensuring the speed of overhaul, so as to make the overhaul work more efficient and effective. The following are the matters to be paid attention to in the maintenance of the steam turbine speed limit device for the 600MW unit:

(1) If the relevant parts are to be disassembled and assembled during the overhaul of the speed governing system, the size and position of each part should be marked and measured during disassembly and assembly, and the relevant records should be made to avoid errors in assembling affecting the performance and characteristics of the regulating system, and the operation effect of the steam turbine cannot be improved. The parts to be marked and measured mainly include adjusting bolts, spring tightness, connecting rods and gaskets.

(2) In dismantling and repairing the speed limit device, the gap distance between each component and component should be measured and recorded to ensure the accuracy of installation. Gaps to be measured and recorded include adjusting valve stroke, adjusting valve rod clearance and bending, piston clearance and stroke, misaligned valve core clearance and over-sealing, etc.

(3) The internal components of the dismantled system should be classified and placed in different parts boxes, especially in the storage of precision parts. Special attention should be paid to the use of clean and soft cloth to wrap them, and the dismantlement and assembly should be handled lightly to avoid damage caused by collision.

(4) In the course of overhaul, the oil chambers and orifices on the slide valves, sleeves, pistons and piston rods should be carefully cleaned and wiped with clean cloth to ensure the cleanliness of these components. At the same time, carefully check whether there are corrosion or cracks in the slide valve, piston ring, piston rod and spring to ensure smooth and complete shoulder of the slide valve.

(5) When installing sliding valves and pistons, lubricate the sliding parts with turbine oil to ensure that the sliding and rotating parts of the parts can operate flexibly without loosening or jamming, so that they can operate flexibly at work and promote the normal play of the speed governing system function of the system.

(1) When installing the sliding sleeve and bushing in speed limit device, first accurately press the ball bearing into the bushing, and then press into the sliding sleeve; after fixing the sliding sleeve, care should be taken to check whether the rotation of the bushing is smooth.

(2) When the flying block is installed, the nut must be tightened by 58.5N. M torque.

(3) The gear stroke adjusting bolt can be temporarily installed for use during commissioning.

(4) When the speed governor is mounted on the pump body, the bonding surface should be coated with a binder to avoid oil leakage.

(5) Because the speed governor is a dual-purpose governor, an operating arm is added to control the speed, so the adjusting bolt on it should not be loosened at will before debugging.

Here are some examples of defects when improperly install the speed governor.

There is a truck crane, after the repair and commissioning of the fuel injection pump installed after the commissioning of the following defects: engine middle speed turpentine throttle, not only cannot reduce the speed, but also faster and faster, like a “flying” mark. After the collapse of the fuel injection pump, it was found that the plunger was misaligned 180 degrees in the direction of the plunger when the plunger was mounted on the sleeve, resulting in the opposite direction of fuel supply and shutdown. When receiving throttle, the fuel supply control rod moves toward the direction of reducing fuel supply, while the plunger moves toward the direction of adding fuel supply, forming that the fuel injection pump cannot operate. After the plunger changes to 180 degrees, the machine is retested and everything is normal.

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