Abstract: Aiming at the problem of water hammer and boost in the use of check valve of common structure, a design scheme of adding auxiliary valve with slow closing is proposed. The improved product has the functions of smooth opening and closing and reducing water hammer pressure. The check valve is used as a valve which is opened when the pipeline system is downstream and closed when the counterflow is closed, which is mainly used to prevent reverse flow of the medium, prevent the pump and the driving motor from reversing and the medium in the container is discharged; The most common is the swing valve flap around the valve body rotation check valve and the valve flap along the vertical center line vertical movement of the lift check valve, but the above two kinds of structure of the valve are closed when the media Backflow speed from the maximum quickly dropped to zero, resulting in a rapid increase in pressure on the side of the pipe inlet, resulting in damage to the pipeline system of water hammer phenomenon, so the general check valve production diameter of 50 ~ 500 mm 〔1〕 . In order to reduce the water hammer effect of the check valve and expand the use range of the check valve, the author designs a slow closing auxiliary valve on the basis of the original product to solve the problem of water hammer boosting in the pipeline. 1, Swing check valve structure to improve the original Swing check valve flap slow relief valve (Figure 1). Deputy valve installed in the main valve flap on the side or both sides and threaded connection, the normal flow of medium valve is opened, the media pressure will open the deputy valve, medium flow through the deputy valve orifice into the main valve outlet, the main valve inlet end Pressure relief, the main valve flap open, the main valve before and after the pressure tends to balance; medium countercurrent, the main valve flap quickly closed under the action of counter-current medium, while the deputy valve body upper buffer cylinder, deputy valve cover screw valve The upper part of the body is covered with a small hole, the auxiliary valve disc and the piston rod are empty with a certain clearance, the piston and the buffer cylinder are sealed with an O-shaped rubber ring, and the plane between the lower part of the piston and the valve disc is sealed; When the valve closes with the main valve flap, the medium gradually flows into the upper chamber of the sub-valve buffer cylinder through the small hole due to the function of the orifice of the sub-valve cover, and part of the medium flows back through the gap between the sub-valve flap and the piston rod , So the secondary valve piston is slowly closed. The closing of the main valve of the structure is equivalent to the quick closing phase, and the slow closing of the auxiliary valve is equivalent to the slow closing phase. According to the hydraulic and mechanical transition mechanism of the pump station, the structure design can effectively prevent the water hammer from increasing. 2, the lift check valve structure Lift lift check valve, also known as the end of the valve, it can maintain pump pumping suction required water column 〔2〕; the valve structure is improved in the main valve flap valve body bracket Add a slow closing valve between the two shown in Figure 2. A pad ring is added between the valve body and the bottom net to increase the height of the valve flap rising; a rubber seal is adopted for the buffer piston and the buffer cylinder, the valve shaft and the piston are rigidly connected, and the gap between the buffer cylinder and the valve disc shaft is small. When the media downstream, the pressure medium to open the valve flap into the main valve cavity, while pushing the buffer piston up; when the media backwards, due to open the buffer cylinder is already full of media inside the opening, and buffer cylinder and valve shaft gap between the more Therefore, with the gradual discharge of the medium in the buffer cylinder through the gap, the main valve flap is closed to play a buffering effect, so as to control the water hammer in the pipe network (FIG. 2). 3, before and after the check valve slow closing structure improvement test results test device shown in Figure 3. Using a calibrated pressure gauge, the pressure transmitter sends the pressure signal to the oscilloscope for recording, and reads the change value of water hammer pressure at each moment on the oscillogram with a calibrated ratio. Figure 4 shows the comparison of the test results of normal structure check valve (a) and ordinary structure check valve with slow closing auxiliary valve (b). Test valve diameter of 100 mm, the system pressure 0.5 MPa, flow 5 L / s. When the pump suddenly stopped, indicating that after the power cut-off valve inlet side pressure - time curve 〔4〕. Figure 4 (a) shows the result of the main valve without slow closing auxiliary valve, the maximum water hammer is increased by 0.53 MPa; Figure 2 (b) is the result when the main valve is slowly closed with the auxiliary valve, the maximum water hammer is increased by 0.04 MPa . 4 Conclusions (1) Main valve flap opening and closing smooth, slow closure Deputy valve structure is compact, reliable performance. (2) The main valve flap slow closure after the first clearance, which can effectively prevent destructive water hammer, expanding the use of check valve. (3) Improve the structure is simple, easy to produce and exchange. (4) Slow closing vice valve can be repaired or replaced, without affecting the use of check valve. Reference book 1, Yang Yuanquan. Valve Design Handbook. Beijing: Mechanical Industry Press, 1992.15 ~ 20 2, Xu Ming Yang. Experimental study on the flow characteristics of liquid controlled retarder butterfly valve. Gansu Science Journal, 1997 (4): 12 ~ Lyons J L. Valve Technical Manual. Beijing: Mechanical Industry Press, 1991.69 ~ 75 4, Shenyang Valve Institute, Hefei Institute of General Machinery. Valve. Beijing: Mechanical Industry Press, 1994.75 ~ 80
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