The exhaust steam of the 300MW feed pump steam turbine is directly connected to the main engine condenser through the exhaust steam pipeline. In order to ensure the reliable isolation of the feed pump steam turbine during the operation of the main engine, an isolation valve is set in the exhaust steam pipe. Because the exhaust pipe has a large diameter and is in a vacuum state, an electric vacuum butterfly valve is selected. The sealing of the valve must be good due to the importance of the location. Otherwise, the vacuum of the unit will be decreased and the economy will decrease.
The steps for adding water are as follows:
(1) After confirming that the exhaust valve is closed well, open the exhaust valve on the upper part.
(2) Open the inlet valve of the sealing water at the bottom and add water to the chambers of the two sealing valves. When the exhaust pipe overflows, close the exhaust valve to keep the sealing water pressure in the chamber.
The maintenance of vacuum butterfly valves
After the unit has been out of service, the maintenance of the vacuum butterfly valve can be started. The maintenance steps are as follows:
(1) Open the manhole door beside the valve.
(2) Open the valve electrically to a fully open position.
(3) Relevant staff shall enter the pipeline to check the valve under the condition of ensuring sufficient lighting. At this time, there should be a person outside the manhole door to supervise and be contacted at any time. If portable lights are used, the voltage should be 12V, and the transformer for portable lights should be placed outside the pipes.
(4) Check the double sealing surface of the valve and the sealing ring on the valve plate. If the sealing ring is seriously damaged during the use of the valve and affects the sealing of the valve, the spare sealing ring should be replaced in time.
(5) After checking that the valve's sealing is in a good condition, check the valve switch stroke and high and low limit. At this time, the staff in the pipeline should carefully check, and after confirming that the limit of the valve's electric switch is fine, take out the tools and other items in the pipeline; evacuate the personnel, and install the manhole door.
The steps for adding water are as follows:
(1) After confirming that the exhaust valve is closed well, open the exhaust valve on the upper part.
(2) Open the inlet valve of the sealing water at the bottom and add water to the chambers of the two sealing valves. When the exhaust pipe overflows, close the exhaust valve to keep the sealing water pressure in the chamber.
The maintenance of vacuum butterfly valves
After the unit has been out of service, the maintenance of the vacuum butterfly valve can be started. The maintenance steps are as follows:
(1) Open the manhole door beside the valve.
(2) Open the valve electrically to a fully open position.
(3) Relevant staff shall enter the pipeline to check the valve under the condition of ensuring sufficient lighting. At this time, there should be a person outside the manhole door to supervise and be contacted at any time. If portable lights are used, the voltage should be 12V, and the transformer for portable lights should be placed outside the pipes.
(4) Check the double sealing surface of the valve and the sealing ring on the valve plate. If the sealing ring is seriously damaged during the use of the valve and affects the sealing of the valve, the spare sealing ring should be replaced in time.
(5) After checking that the valve's sealing is in a good condition, check the valve switch stroke and high and low limit. At this time, the staff in the pipeline should carefully check, and after confirming that the limit of the valve's electric switch is fine, take out the tools and other items in the pipeline; evacuate the personnel, and install the manhole door.
Next: Common Failures of Butterfly Check Valves
Previous: Problems Occurred in High-temperature and High-pressure Valves
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