Pressure test of industrial valves is a key link to ensure its performance and safety. Different types of valves need to use targeted pressure test methods due to structural differences. The following guidelines combine general principles with specific valve types to provide complete pressure test operations:

First, the general pressure test principle

Scope of application

New valves are usually only tested for tightness, but repaired or corroded valve bodies/caps should be tested for strength.

The safety valve should be tested according to the instructions and specifications, such as constant pressure and return pressure.

Inspection ratio

Low-pressure valve sampling 20%, unqualified is full inspection; Medium and high pressure valves need to be 100% inspected.

Test medium

Commonly used media include water, oil, air, steam, nitrogen and so on. The safety valve is selected according to the medium type (such as saturated steam for steam, air for gas).

duration

The strength/tightness test is generally 2-3 minutes, and the important valve is extended to 5 minutes; The small diameter valve time is shortened, and the large diameter is extended.

Two, the specific valve pressure test method

1. Ball Valve

Strength test: Ball half open state, from one end of the injection medium to the specified pressure, check the valve body/cap leakage.

Tightness test:

Floating type: semi-open rotating ball, check the packing and gasket when closed; Repeat the experiment from the other end.

Fixed: closed state injection medium, with pressure gauge (accuracy 0.5-1, measuring range 1.5 times test pressure) detection; Half open check inner cavity seal.

Three-way ball valve: Seal test at all locations.

2. Gate valve

Strength test: same as stop valve.

Tightness test:

Intermediate pressure test: open the ram pressure boost after closing, take out to check the seal on both sides; Or inject the medium to the plug detection (DN32mm below should not be used).

Blind plate inspection method: close the gate after pressure increase, open one end of the blind plate to check the sealing surface, repeat the test.

3. Check valve

Test status: lift valve disc axis is vertical, swing channel/valve disc axis is approximately horizontal.

Strength test: Inject medium from inlet end to check valve body/cap leakage.

Tightness test: Inject medium from the outlet end, check the inlet end sealing surface, packing and gasket.

4. Butterfly valve

Strength test: same as stop valve.

Tightness test: open the plate injection medium, check the packing and sealing; Check disc seal after closing.

Exception: Butterfly valves for regulating flow can be used without sealing test.

5. Plug valve

Strength test: Inject the medium from one end, close the rest of the way, rotate the plug to the full open position to check for leakage.

Tightness test:

Straight-through type: keep the pressure in the cavity equal to the path, rotate the plug to the closed position for inspection; Repeat the 180° test.

Three-way/four-way: Introduce pressure from the right Angle end and check other end seals.

Allow to apply non-acidic lubricating oil, test time 1-3 minutes; Gas plug valve needs 1.25 times the working pressure air seal test.

6. Diaphragm valve

Strength test: Inject the medium from either end, open the disc, and check the valve body/bonnet for leakage.

Tightness test: Close the valve disc after pressure reduction and check the leakage at the other end.

7. Pressure reducing valve

Strength test: single or assembled test, bellows after welding to 1.5 times the highest pressure air test.

Tightness test:

Air/Water: 1.1 times nominal pressure.

Steam: Maximum pressure at operating temperature.

Inlet and outlet pressure difference ≥0.2MPa, adjusting screw to make the outlet pressure sensitive change, no stagnation or blocking.

Steam reducing valve: The export pressure appreciation within 2 minutes after closing the cut-off valve shall meet the requirements, and the pipeline volume behind the valve shall meet the standards.

Water/air pressure reducing valve: Close when outlet pressure is zero, no leakage within 2 minutes.

8. Safety valve

Strength test: water test, the lower part of the valve body from the inlet end to introduce pressure, the upper part from the outlet end to introduce pressure.

Tightness test: nominal pressure value, not less than two times, no leakage within 5 minutes.

Method of leak inspection:

Butter tissue paper method: Tissue paper bulges to leak.

Irrigation method: no bubbling in water is qualified.

Constant pressure/return pressure test: not less than 3 times, in line with GB/T 12242 standard.

Three. Key points to note

Installation position: The valve should be placed in an easy to check direction.

Welded valves: When blind plate pressure test is not feasible, cone or O-ring sealing is used.

Hydraulic test: try to eliminate air to avoid errors.

Boost: Gradually boost the pressure to avoid damage to the device caused by sudden pressure increase.

Closing force: Only one person is allowed to close with normal physical strength, and two people are allowed to operate when the handwheel is ≥320mm.

Upper seal valve: take out the packing for sealing test, check the leakage after the upper seal is closed (observe the filling box during the gas test).

Record and mark: record and mark after pressure test (√ qualified, × unqualified), pile separately, cover protection.

Four. Special Instructions

Throttle valve: do not do closure seal test, but need to carry out strength test and packing/gasket seal test.

Test medium selection: according to valve type and medium characteristics (such as saturated steam with steam safety valve).

Holding time: the shell strength test holds the pressure for 5 minutes, and the upper seal test holds the pressure according to the DN size (15s-120s).

Following the above methods can ensure the standardization and effectiveness of various industrial valve pressure tests and ensure the safe operation of industrial equipment.