Editor's note: The pressure relief valves, emergency shut-off valve and emergency valve is open and applications in recent years the development of valves, water supply has been building and fire circles, issues relating to its setting on the views of their own.
1 pressure relief valve
Pressure relief valve installed in the fire service pump outlet pipe, the normal shut down, the fire more than the pressure of water supply network settings automatically when turned on, water supply system in order to prevent damage due to overpressure.
Fire to the water distribution network of over-pressure was mainly due to the following reasons: ① design flow selected by the fire pump flow - lift curve is steep type, in a small flow of run-time (the initial self-test or fire) will appear overpressure; ② pumps due to a sudden it (such as power failure) stop transfer, delivery and did not take appropriate technical measures to stop pump water hammer caused by overpressure.
Pressure relief valve settings should pay attention to the location, caliber choice, pressure and the corresponding annex to configuration settings and so on.
① pressure relief valve may be located in the vicinity of the fire pump or water tank near the fire. Automatic sprinkler system design specifications "GBH84-1985 amendment to Article 10.3.3 of the送审稿requirements:" ... ... each pump control valve outlet pipe should be set up ... ... and, if necessary, pressure relief valve should be located. "Approval of the provision in the draft was changed to: "... ... when necessary, should be taken to control the pump outlet pressure for the measure." These measures which includes the pressure relief valve.
When the pressure relief valve installed in the outlet pipe when the fire pump can be located in a non-return valve before and after. Before a non-return valve located in a small flow of water running digestion caused by excess pressure, and after in a non-return valve (along the direction of flow) due to not only remove a small flow of water caused by running the overpressure, but also remove from the parked pump water hammer caused by excess pressure, even if the fire pump outlet pipe to stop the elimination of not taking other measures to pump water hammer (speed closed check valve, relief check valve closed, the buffer tank, etc.), will not cause harm and loss.
② There are two pressure relief valves caliber practice, a mains water supply with fire or with the Path 1, and the other is DN100 or DN150 using the pressure relief valve.
From the relief perspective, the greater the diameter of the pressure relief valve pressure relief sooner, the better. As shown in Figure 1, Q for the vent flow, large diameter pressure relief valve, Q value on big, RBC curve tend to the right, R and H curve curve intersection point M will be shifted to right, the pressure decreases. However, from the economic point of view, the larger caliber, higher prices, and more pressure relief valve, will inevitably increase the cost of project construction. Proceeding from reality and therefore, the current preference for a fixed diameter of pressure relief valves, pressure relief even when the actual pressure value slightly larger than large diameter of the actual relief valve pressure relief, but the effect is still feasible. Therefore, the pressure relief valve diameter can be used for the following: If the fire water mains diameter D ≤ 150mm, while the use of the pressure relief valve DN100; diameter mains water supply if the fire D> 150mm, while the use of the pressure relief valve DN150.
③ the pressure relief valve settings should be higher than the main fire pump and pressure regulator pump settings. When a regulator pump, the pump start and shut down two pressure regulator value (refer to regulator pressure pump run-time value). Regulators stopped pump pump water hammer pressure relief valve easily lead to misuse of open, so the stable high-pressure fire water supply system to eliminate a good reliable pump water hammer stop the technical measures, and should review the fire to the water distribution network in the water after the hammer residual pressure below the pressure relief valve settings to ensure that misuse does not open.
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