How to set up pressure relief valve, emergency shut-off valve and opening valve

Summary of the design of pressure relief valve, tight closing valve and pressing open valve: Pressure relief valve, tight closing valve and tight open valve are the valves developed and used in these years. They are highly valued by the construction and fire water supply industry. The question talked about one's own opinion.
 Key words: Pressure relief valve, tight closing valve, tight opening valve, hydraulic control valve, fire protection
    1 pressure relief valve
    The pressure relief valve is arranged on the fire water pump outlet pipe, which is normally closed. When the pressure of the fire water supply pipe network exceeds the set value, it is actively opened to avoid damage to the water supply system due to overpressure.
    The overpressure of the fire water supply network is mainly due to the following reasons: 1 The flow rate of the pump is selected according to the fire plan flow rate—the head curve is attributed to the steep type, and the overpressure will be presented during the small flow operation (self-test or pre-fire); Therefore, (such as power outage) stop, the outlet pipe has not adopted the corresponding technical measures, stop pumping water hammer to form an overpressure.
    Pressure relief valve settings should pay attention to the orientation, caliber selection, pressure setting and corresponding accessories and equipment.
    1 Pressure relief valve can be located adjacent to the fire pump or adjacent to the fire water tank. The Code for Planning of Active Water Spray Rescue System GBH84-1985 Revised Article 10.3.3 Rules for the review: “Each group of pumps...The outlet pipe should be equipped with a control valve... If necessary, a pressure relief valve should be provided.” In the approval draft, it was changed to: "... When necessary, the method of controlling the outlet pressure of the water supply pump should be adopted." These methods include a pressure relief valve.
    When the pressure relief valve is installed on the fire pump outlet pipe, it can be placed before and after the check valve. It is set before the check valve to eliminate the overpressure generated by the small flow of the pump, and after the check valve (in the direction of the water flow), it can not only eliminate the overpressure caused by the small flow of the pump, but also eliminate the pump stop. The overpressure formed by the water hammer does not cause damage or loss even if the fire pump water outlet pipe does not adopt other methods for eliminating the water hammer of the pump (speed closed check valve, slow closing check valve, buffer tank, etc.).
    2 The pressure relief valve has two methods, one is the same diameter as the fire water supply main pipe or the first one, and the other is the pressure relief valve of DN100 or DN150.
    From the point of view of pressure relief, the larger the diameter of the pressure relief valve, the faster the pressure relief and the better the effect. As shown in Fig. 1, Q is the discharge flow, the diameter of the pressure relief valve is large, the Q value is large, the RBC curve tends to the right side, and the intersection point of the R curve and the H curve is also shifted to the right, and the pressure value thereof decreases accordingly. However, from an economic point of view, the larger the caliber, the higher the price of the pressure relief valve, which inevitably increases the construction cost. Therefore, starting from practice, it is now preferred to use a fixed-diameter pressure relief valve. Even if the actual pressure value during pressure relief is slightly larger than the actual pressure value of the large-diameter pressure relief valve, the induction effect is still feasible. Therefore, the pressure relief valve diameter can be made as follows: If the fire water supply pipe diameter D ≤ 150mm, the DN100 pressure relief valve is used; if the fire water supply pipe diameter D> 150mm, the DN150 pressure relief valve is selected.
    3 The pressure setting of the pressure relief valve should be higher than the pressure setting of the fire main pump and the constant pressure pump. When there is a constant pressure pump, there are two pressure values for the starting and closing voltage regulator (refer to the pressure value when the pressure pump is running). The pressure of the pump stop water hammer pressure is easy to form the pressure relief valve is open, so the technical solution for eliminating the pump water hammer should be perfected for the steady high pressure fire water supply system, and the fire water supply network should be reviewed in the water hammer. If the residual pressure is lower than the pressure setting of the pressure relief valve, it can be guaranteed not to open.
    4 The pressure relief valve shall be placed on the branch pipe connected to the fire water supply main pipe. In order to facilitate the maintenance of the pressure relief valve and to avoid misclosing of the control valve, a signal gate valve or a signal butterfly valve should be provided before the pressure relief valve. In order to maintain the flow of water when the pressure relief valve is repaired, a bypass pipe should be provided.
2 pressing closed valve
    The tight closing valve is normally open, and the pipe network pressure is actively closed when the pressure exceeds the set value of the pressure to avoid the fire water entering the water tank when the fire pump is running. Together, the water supply fittings in the day-fire-fighting water supply system can be avoided. Damaged by overpressure.
    China's referral days and fire water sharing system. The pressure value of the pump is usually low when the system is started. The pressure value of the fire pump when the fire is fired is much higher than the pressure value when the pump is started. According to the fourth rule of Article 8.6.3 of the Fire Code for Repairing Construction. "After a fire, the fire water supplied by the fire pump should not enter the fire water tank." To solve this problem, a tight closing valve should be placed on the pipe entering the fire water tank (Figure 2). In order to avoid overpressure of the water supply fittings when the fire pump is started, an urgent closing valve should be provided on the water supply pipe.
    The problem with pressing the closed valve is the pressure setting. If the pressure is set too low, the tight closing valve will be closed when the pump is started; if the pressure is set too high, the closed valve will not be closed when the fire pump is started. Generally, the pressure setting value should be higher than the pressure value at the zero flow of the day pump and lower than the pressure value when the fire pump is planning the flow value. A technical approach to the water main must be adopted together to avoid water hammer.
    3 pressing open valve
    The urgently open valve is used in the water spray rescue system and has not yet been implemented in the project. The urgently open valve is normally closed, and the water is actively opened when the pipe network pressure reaches the pressure set value, in order to avoid the water spray phenomenon caused by the low pressure before the fire pump reaches the extra speed before the fire pump reaches the extra speed.
    The valve provided by the fire water supply pipe is mostly open, and the open open valve requires normally closed, that is, the additional speed is reached after the fire pump is started, and the pipe network pressure is open when it reaches the planned pressure value, which requires the valve to open and close. Normal, OK*. The tight open valve is similar in nature to the pressure relief valve and is open when the pressure value is reached. The difference is that after the pressure relief valve is opened, the water discharges or returns to the fire pool to relieve pressure; after the open valve is opened, the water flows into the water spray to save. The living system is used for saving. Both are attributed to the field of hydraulic control valves, which are provided with a needle valve for the pilot, and the needle valve is easy to block due to the obstruction of impurities; there are barriers for operating the valve flap, the rubber is raw material, easy to aging and wear. The corresponding measures adopted for these two components are: 1Set multi-stage filter in front of the needle valve, the filter mesh hole is gradually reduced to intercept solid particle impurities; 2The rubber barrier is made of high quality products, and the barrier is regularly viewed. And the case of hydraulically operating the valve in the spring.
    Now, the pressure relief valve, the tight closing valve and the urgently open valve are treated as general-purpose valves, but not included in the field of fire-fighting valves, and need not be inspected by the fire product quality supervision and inspection center. The author believes that this situation should be changed. Pressure relief valves, tightly closed valves and tightly open valves are only used in fire water supply systems, and should be classified as fire protection products as soon as possible.