CE certification review team to hebei tongli company for review!2019-07-23
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First, the installation
1. When installing the pressure reducing valve, the filter must be installed in front of the valve, and the filter screen should use stainless steel mesh of 60 mesh or more;
2. A trap should be installed before the pressure reducing valve to remove the condensate from the pipeline. If the pipeline behind the pressure reducing valve is turned upward, the trap must also be installed at a low position.
3. The pressure relief valve should be connected to the bypass valve (connected to the filter) before and after the pressure relief valve. The bypass valve line should be lower than the pressure relief valve.
1. The differential pressure before and after the pressure reducing valve should be ≥0.2MPa;
2. When the medium in the pressure reducing valve is steam, before starting the commissioning, first open the bypass valve to remove the accumulated water in the pipeline, then pass the steam. After the whole valve has become hot, slowly turn the uppermost adjusting bolt slowly. Adjust the valve;
3. For pressure reducing valve with diameter ≥ DN65, open the bypass valve before adjusting, so that the pressure behind the valve is close to the required pressure value, then close the bypass valve and adjust the pressure reducing valve. This avoids valve flap hopping (repeated humming) due to sudden changes in pressure behind the valve, which can damage the valve sealing surface.
Third, the problems that are easy to occur in the use of pressure reducing valves
1. The gas or pressure behind the valve does not reach the required value. The reason is that:
1. The filter can not effectively filter the impurities, so that the small air holes (feedback holes) in the valve are blocked, resulting in the small amount of air passing, which makes it difficult for the piston to push open the main valve flap;
2. The bypass line is higher than the pressure reducing valve, and the impurities therein fall into the pressure reducing valve, blocking the small through hole;
3. The gasket used when the flanges at both ends of the pressure reducing valve are connected to the pipeline is blown into the small air passage by the pressurized steam to cause blockage.
4. Due to the sudden receipt of high temperature steam, the piston ring expands too much and causes a plug.
5. Since the trap is not installed in the pipeline, the water in the inlet or outlet pipeline is blown into the upper part of the piston by the airflow, which causes the upper pressure of the piston to be low, and it is difficult to push open the main valve.
2. The pressure before and after the valve is the same (no decompression). The reason is that:
1. The filter mesh has a large aperture, which cannot effectively filter the impurities in the pipeline, so that impurities or gaskets are stuck at the sealing surface of the main valve disc to cause leakage;
2. The valve failed to preheat effectively before commissioning. The sudden increase of temperature caused the expansion ratio of the piston ring to be too large, which caused the piston to move up and down inflexibly, blocked the up and down movement of the main valve flap, and could not perform decompression and pressure regulation.
3. The piston ring is jammed so that the piston cannot move up and down in the cylinder.
4. The downward compression of the adjusting bolt is too large, which causes the diaphragm to lose its elasticity.
3. The pressure behind the valve is unstable. The reason is that:
1. There is no trap installed in the pipeline. There is too much condensed water in the pipeline, which is accumulated in the valve body cavity and causes pressure instability.
2. The diameter of the pressure reducing valve is not suitable, and the input steam quantity is too different from the steam consumption.