The pipe diameter of the circulating water system is quite large due to the large amount of cooling water required by thermal power plants. The nominal diameter of the main pipe of the circulating water of the 300MW unit is DN2600. The nominal diameter of the inlet and outlet valves of the circulating water of the main condenser is DN1800. Butterfly valves have become the first choice for opening, closing and regulating valves in low-pressure and large-diameter pipeline systems due to their compact structure, small sizes and good sealing performance.
The working pressure of DF47DH-1.0 butterfly valves of DN1800 is less than and equal to 1.0MPa, and it is suitable for water with temperatures less than and equal to 50℃. The valve and the pipeline are connected by flange, and the secondary reduction device is adopted. The valve is arranged vertically. The butterfly valve is mainly composed of a valve body with a positioning block, a butterfly plate, an upper and lower valve shaft and a transmission device.
The working principle is that the motor drives the valve stem to rotate, and then drives the valve shaft and the butterfly valve to rotate within a range of an angle of 90 relative to the valve body to achieve the purpose of controlling flow and opening and closing.
Because most of the isolation valves of the circulating water main pipe are arranged in the outdoor valve wells, the working environment in the valve wells is very poor, and there is a lot of steam, which makes the control circuit of the electric device fail, making the limit of the valve ineffective, and causing the valve to be over closed. In actual use, the electric device should be replaced with an outdoor type to ensure reliable switching and adjustment of the valve in harsh environments.
The overhaul of butterfly valves of circulating water
Before the system is isolated, the appearance of the valve can be checked. First, the water in the valve well should be removed. Then, check the tightness of the connecting flange of the valve. At this time, the pipeline should be filled with water and there is pressure; the flange of the valve should be connected tightly without leakages. After the system is reliably isolated, the valve can be overhauled. The repair steps are as follows:
(1) Make sure that the water in the pipeline has been removed.
(2) Open the valve to the fully open position electrically, and turn the power off.
(3) The staff enters the pipeline through the condenser's manhole door to check the sealing surface of the valve (sufficient lighting should be ensured). At this time, there should be a special guardian outside the manhole door, and they should be able to be called at any time. Portable lights with 12V or explosion-proof power supply should be used in the pipeline to ensure the safety of personnel.
(4) If the valve's sealing ring is seriously damaged, it should be replaced. Prepare the spare parts of the same type of sealing ring. Then, remove the bead screw of the original sealing ring; remove the bead and take out the damaged sealing ring. Install the spare sealing ring, the sealing ring bead and bolts.
After making sure the sealing ring is not damaged and the valve is well sealed, the valve can be turned on to check the high and low limits of the valve. At this time, there should be personnel staying in the pipeline to observe the valve limit, especially the lower limit. If the valve limit is not accurate, it should be re-calibrated.
(5) Check the limit of the valve. After it can be opened and closed, the personnel should be evacuated and take out the tools; the manhole door should be installed, and the valve inspection is completed.
The working pressure of DF47DH-1.0 butterfly valves of DN1800 is less than and equal to 1.0MPa, and it is suitable for water with temperatures less than and equal to 50℃. The valve and the pipeline are connected by flange, and the secondary reduction device is adopted. The valve is arranged vertically. The butterfly valve is mainly composed of a valve body with a positioning block, a butterfly plate, an upper and lower valve shaft and a transmission device.
The working principle is that the motor drives the valve stem to rotate, and then drives the valve shaft and the butterfly valve to rotate within a range of an angle of 90 relative to the valve body to achieve the purpose of controlling flow and opening and closing.
Because most of the isolation valves of the circulating water main pipe are arranged in the outdoor valve wells, the working environment in the valve wells is very poor, and there is a lot of steam, which makes the control circuit of the electric device fail, making the limit of the valve ineffective, and causing the valve to be over closed. In actual use, the electric device should be replaced with an outdoor type to ensure reliable switching and adjustment of the valve in harsh environments.
The overhaul of butterfly valves of circulating water
Before the system is isolated, the appearance of the valve can be checked. First, the water in the valve well should be removed. Then, check the tightness of the connecting flange of the valve. At this time, the pipeline should be filled with water and there is pressure; the flange of the valve should be connected tightly without leakages. After the system is reliably isolated, the valve can be overhauled. The repair steps are as follows:
(1) Make sure that the water in the pipeline has been removed.
(2) Open the valve to the fully open position electrically, and turn the power off.
(3) The staff enters the pipeline through the condenser's manhole door to check the sealing surface of the valve (sufficient lighting should be ensured). At this time, there should be a special guardian outside the manhole door, and they should be able to be called at any time. Portable lights with 12V or explosion-proof power supply should be used in the pipeline to ensure the safety of personnel.
(4) If the valve's sealing ring is seriously damaged, it should be replaced. Prepare the spare parts of the same type of sealing ring. Then, remove the bead screw of the original sealing ring; remove the bead and take out the damaged sealing ring. Install the spare sealing ring, the sealing ring bead and bolts.
After making sure the sealing ring is not damaged and the valve is well sealed, the valve can be turned on to check the high and low limits of the valve. At this time, there should be personnel staying in the pipeline to observe the valve limit, especially the lower limit. If the valve limit is not accurate, it should be re-calibrated.
(5) Check the limit of the valve. After it can be opened and closed, the personnel should be evacuated and take out the tools; the manhole door should be installed, and the valve inspection is completed.
Next: Problems Occurred in High-temperature and High-pressure Valves
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