Axial flow check valve has disc type and ring disc type structure. The valve should have a reasonable flow channel profile, small opening pressure and pressure drop, and large flow capacity. The disc type structure (Fig. 1) of the axial flow check valve spool is simple and easy to process, but the moving spool is a cantilever structure. When the valve diameter is large, due to the weight and volume of the spool disc, the spool will It is easy to get stuck when moving, so the axial flow check valve with DN≤250 is mostly disc type structure, and the axial flow check valve with DN≥300 is mostly ring disc type structure (Figure 2). The ring-disc structure overcomes the shortcomings of the disc type, the valve core is light and flexible, but the structure is complex, the valve core is annular, the sealing surface is large, the leakage surface is many, and it is not easy to seal.

Test plan

Large-diameter axial flow check valves are usually used at the outlet of large pump units and large compressor units to prevent backflow of media and protect pump units and compressor units. When the unit is stopped or switched, the time for the medium to change from the forward flow to the reverse flow is shorter, the flow rate is larger, and the kinetic energy of the reverse flow of the medium is larger, which is easy to form an initial seal and an effective seal. Flow capacity, cracking pressure, and pressure drop are the key performance indicators of check valves. The opening pressure and pressure drop are small, and the power consumption of the unit is less. In order to obtain a small opening pressure and pressure drop for the axial flow check valve, the stiffness of the return spring on the spool is designed to be as small as possible. This results in low initial sealing force, high leakage, and difficulty in establishing differential pressure. Therefore, the sealing performance of the high-pressure large-diameter axial flow check valve cannot be tested by the conventional pressure test method.

The sealing test plan of the axial flow check valve should be combined with the actual working conditions and standard test methods to truly assess the sealing performance of the check valve and other performance indicators. The test protocol should consider three aspects. ①Simulate the operating conditions of the check valve, and quickly fill the outlet port of the check valve with a medium with a certain pressure and flow. ②Use the isolation valve to seal the outlet of the check valve. ③Pressurize the outlet of the check valve to 1.1PN for sealing test.

test system

(1) Test system

The test system (Fig. 3) consists of water pump, safety valve, surge tank, quick-opening valve, isolation valve, pipeline and pressure gauge. Use a water pump to fill the surge tank with water, so that the pressure of the air in the upper chamber of the surge tank rises to 0.8MPa. Open the quick-open valve to quickly fill the outlet of the axial flow check valve with water, and maintain a pressure difference of ≥0.5MPa. Close the isolation valve, turn on the booster pump, increase the pressure in the outlet chamber of the axial flow check valve to 1.1PN, and check for leaks.

(2) Test bench equipment parameters

A special test bench is required for the detection of high-pressure large-diameter axial-flow check valves (Figure 4).

Tested check valve class900, 36in. (PN150, DN900)

Initial sealing pressure 0.5MPa

Voltage Stabilizer V=5m3, Ps=1.0MPa

Water pump Q=350m3/h, H=100m

Inlet pipe diameter DN=150mm

Quick opening valve PN=1.6MPa, DN=150mm

Isolation valve class900, 8in. (PN150, DN200)