The exhaust gas from the 300MW pump turbine is directly connected to the main condenser through the exhaust pipe. In order to ensure that the pump turbine can be reliably isolated during the operation of the main engine, the exhaust pipe is provided with an isolation valve. Because the diameter of the exhaust pipe is large and in a vacuum state, an electric vacuum butterfly valve is selected.
Due to the importance of its location, the tightness of the valve must be good, otherwise the vacuum of the unit will be reduced and the economy will be reduced.
The steps for adding water are:
(1) After confirming that the exhaust valve is closed, open the exhaust valve on the upper part of the valve.
(2) Open the sealed water inlet valve at the bottom of the valve to add water to the chambers of the two sealed valves, and when the exhaust pipe overflows, close the exhaust valve to maintain the sealed water pressure in the chamber.
(II) Vacuum butterfly valve maintenance
After the unit has been decommissioned and the valve has the maintenance conditions, the maintenance of the vacuum butterfly valve can be started. The steps of the maintenance work are as follows:
(1) Open the manhole door next to the valve.
(2) Open the valve electrically to the fully open position.
(3) Under the condition of ensuring sufficient lighting, the relevant personnel enter the pipeline to inspect the valve. At this time, there should be special guards outside the manhole door and contact at any time, and you must not leave. If a running light is used, the voltage should be 12V and the running light transformer should be placed outside the pipe.
(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 seal ring should be replaced in time.
(5) After checking that the valve is intact, check the valve switch stroke and the high and low limits. At this time, the staff in the pipeline should carefully monitor and check to confirm that the normal operation of the valve electric switch is correct. Then remove the tools, appliances and other items in the pipeline, evacuate the personnel, and reinstall the manhole door.