How to test pressure for various valves?

Under normal circumstances, industrial valves are not subjected to strength tests when in use, but the body and bonnet or the valve body and bonnet damaged by corrosion should be tested for strength after repair. The valve strength test and valve sealing test should be done on the valve hydraulic test bench before the valve is installed. This paper will introduce the methods for various industrial valves.

 

Pressure test method for globe valve and throttle valve

 

In the strength test of the shut-off valve and the throttle valve, the assembled valve is usually placed in a pressure test rack. After the valve disc is opened, the medium is injected to the specified value, and the valve body and the valve cover are checked for sweat and leakage. The strength test can also be performed on a single piece. Only shut-off valves are used for sealing test. During the test, the valve stem of the hydraulic shut-off valve is in a vertical state, when the valve flap is opened, the medium is introduced from the bottom end of the valve flap to the specified value. Check the packing and gasket and close the valve flap after passing the test, and open the other end to check for leakage.  The strength test can be done first if both the valve strength and tightness tests are to be done, then reduce the pressure is to the specified value of the tightness test, and check the packing and gaskets, then close the valve flap and open the outlet end to check whether the sealing surface is leaking.

 

Pressure test method of gate valve

 

The strength test of gate valve is the same as that of globe valve. There are two methods for the sealing test of the gate valve.

 

① Open the gate to increase the pressure in the valve to the specified value, then close the gate and immediately take out the gate valve to check whether there is any leakage at the seals on both sides of the gate or directly inject the test medium into the plug on the valve cover to the specified value, and check the seals on both sides of the gate. The above method is called intermediate pressure test. This method is not suitable for sealing test on gate valves with nominal diameter below DN32mm.

 

② Another method is to open the gate to increase the test pressure of the valve to the specified value, then close the gate and open the blind plate at one end to check whether the sealing surface is leaking. Reverse the head and repeat the above test until it is qualified.

 

Pneumatic gate valve packing and gasket sealing test should be carried out before the gate sealing test.

 

Pressure test method of stainless steel ball valve

 

Stainless steel hydraulic ball valve and gate valve are the same type of valve. The difference is that its closing part is a sphere. The sphere rotates around the center line of the valve body to achieve opening and closing. The strength test of the hydraulic actuated ball valve should be carried out with the ball valve for hydraulic system half open.

 

① Stainless steel ball float valve tightness test: put the valve in a half-open state and introduce the test medium at one end, and close the other end. Rotate the ball several times, open the closed end when the valve is in the closed state, and check the sealing performance at the packing and gasket at the same time. There must be no leakage. Then introduce the test medium from the other end and repeat the above test.

 

② Ball check valve test state: lift check valve disc axis is in a position perpendicular to the horizontal; Swing check valve channel axis and disc axis are in a position approximately parallel to the horizontal line.

        

In the strength test, the test medium is introduced from the inlet end to the specified value, and the other end is closed. It is qualified to see if the valve body and bonnet have no leakage.

       

③ The3 way stainless ball valve should be tested for tightness at each position.