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Maintenance method and steps of power plant traps 2020-03-30


1 Introduction

 

The steam drainage system of the steam turbine is an important part of the thermal system of the steam turbine, especially the steam turbine body, main steam, reheat steam, high and medium pressure valves, and steam steam to the pump steam turbine. Some important steam drain valves are required when the unit starts the warming pipe. It can be drained in time and normally, and when the unit is in normal operation, the valve must be reliably isolated without leakage. If these traps leak, the effect on the efficiency of the unit is very obvious.

 

In view of this, some important traps are imported valves, and their structure is a two-position globe valve with air control operation. The globe valve has the advantages of simple structure, good sealing and more maintenance. The globe valve is equipped with a pneumatic control mechanism to make the valve operate quickly and sensitively, which can better meet the requirements of unit automation control.

 

2, Trap maintenance

 

Because the valve is composed of the operating mechanism and the valve body, disassembly is performed in two steps.

 

(1) Removal of the operating mechanism.

 

 Remove the compressed air pipe inlet connector, solenoid valve, action switch and other peripheral components connected to the air control operating mechanism, and place them in a fixed position.

 

Remove the manual operation device of the operating mechanism and set it up.

 

All spring compression bolts on the top of the operating mechanism are loosened.

 

Loosen the fastening bolts where the operating mechanism is connected to the valve stem, and move the fastening ring slightly upwards.

 

Loosen the connecting bolts on the Huff lock block that fixes the operating seat to the valve body, remove the two lock blocks respectively, connect the two lock blocks with bolts, and place them.

 

Use a wrench to loosen the connecting nut of the valve door rod and the operating mechanism until the operating mechanism is disconnected from the valve body, and the operating mechanism is set and placed.

 

(2) Disassembly of the valve body.

 

Use an Allen wrench to loosen and remove the fastening bolt on one side of the bonnet, screw in the fastening bolt from the other side through the thread, and place a piece of iron about 1mm thick in the middle slot of the bonnet fastening. Plate (diameter 3535 ~? 40), tighten the fastening bolts with an Allen wrench, and further open the slot of the valve cover to increase the gap.

 

 Using a special wrench (or rubber hoe) to pull (or knock) the door cover, make the door cover rotate counterclockwise until it is removed and placed.

 

Tap the outside of the stuffing gland with a copper rod until it is loose, and remove the stuffing gland.

 

Remove the door rod and door core and place them in a fixed position.

 

(3) Check. After the valve is completely disassembled, the sealing surface of the valve and other parts should be inspected.

 

 Valve line inspection on valve seat and door core: Visual inspection The valve line seal should be in contact with the entire circumference, and there should be no grooves, blowouts and other defects affecting the seal.

 

The sealing surfaces between the valve stem, the valve housing and the packing gland shall be in good contact.

 

The inlet and outlet of the valve should be free of foreign matter and impurities.

 

(4) Maintenance treatment.

 

If the valve line is blown, the valve core and the valve line in the valve seat should be treated differently: the valve line on the valve core is turned out on the lathe at the original angle; the valve line on the valve seat is repaired exclusively The tool repairs the hard alloy sealing surface in the valve seat. The amount of each repair is about 0.05 ~ 0.08mm. The amount of repair is determined according to the actual situation of the valve line defect. After observing that there are no dents on the sealing surface, the valve wire is finely ground with an abrasive paste. After the valve wire is polished, the blue oil (or red dandelion powder) is evenly applied on the sealing surface on the door core, and it is fixed with a special sleeve and sent to the valve seat for sealing contact test. The sealing surface should be uniform and uninterrupted throughout the entire circumference.

 

If the filler in the stuffing box is non-flexible graphite filler, it should be replaced with flexible graphite filler. If the original graphite filler is flexible, it should be inspected for damage, and if it is damaged, it should be renewed.

 

The sealing surface (contact with the packing) on ??the door stem should be bright and rust-free, and the self-sealing surface in the valve seat and the lower part of the stuffing box should be polished.

 

 The connecting thread surface on the top of the door rod should be clean and the connection should be flexible.

 

The threaded connection of the packing compression sleeve should be cleaned to make it easy to move. To ensure that it can be easily adjusted during normal operation of the unit.

 

(5) Reinstall. After the cleaning and inspection work is completed, all the connecting threads are coated with anti-biting paint, and then the valve can be replaced. Reassembly is performed in the reverse steps of the disintegration procedure.

 

(6) Adjustments and precautions.

 

 After the control mechanism is connected to the valve stem, the lower limit of the valve (the direction of closing) is adjusted at the beginning. When in the connecting nut of the screw-rotation mechanism of the door rod, directly connect the compressed air to the inlet of the operating mechanism, switch the valve, and adjust the connecting nut until the valve is closed. A gap of 3 to 5 mm is left in the lowermost section. At this point, the preliminary adjustment is completed (at this time, the Huff lock block is not installed).

 

After the air control opens the valve to make the control seat and valve body tightly connected, install the Hada lock block and tighten the fastening bolts.

 

Pneumatic control opens and closes the valve, and adjusts the opening indicator of the valve so that the position of the pointer of the valve matches the actual position of the valve.

 

After the peripheral equipment such as the solenoid valve and the action switch are installed, work with the thermal control professional to adjust and verify the switch signal indication, confirm that the opening and closing directions are correct, and the adjustment is complete.


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