Comprehensive Guide to Industrial Valve Pressure Testing
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Valve pressure testing is a critical step in verifying the performance and safety of industrial valves under actual operating conditions. The testing methods vary depending on the type, structure, and application of the industrial valve. Generally, valve pressure testing is divided into two main categories: strength tests and sealing tests. These tests ensure that the valve can withstand operational pressures and prevent leaks. Below, we introduce the pressure testing methods and specific steps for several common types of valves to help you understand how to properly conduct these key tests.
Pressure Testing Methods for Ball Valves
A ball valve is a valve that controls the flow of fluid through a ball, suitable for frequent on-off occasions and has good sealing performance. The pressure testing process of a ball valve is usually divided into strength tests and sealing tests.
1. Ball Valve Strength Test
The strength test of a ball valve should be carried out with the ball in a semi-open state to ensure the strength of the entire valve body under pressure.
2. Ball Valve Sealing Test
The sealing test for ball valves depends on the valve’s structure and includes two main types:
Floating Ball Valve Sealing Test
With the valve half-open, introduce the test medium from one end and seal the other. Rotate the ball several times, then close the valve. Open the sealed end to check for leaks, while also inspecting the seals at the packing and gaskets. No leakage indicates a pass. Repeat the test from the other end.
Fixed Ball Valve Sealing Test
Before testing, rotate the ball a few times without load. With the valve in a closed position, introduce the test medium from one end to the specified pressure. Check the sealing performance at the inlet end with a pressure gauge. If there is no pressure drop within the specified time, the valve passes. Repeat the test by introducing the medium from the other end.
For three-way ball valves, conduct sealing tests in all positions to ensure compliance in all directions.
Pressure Testing Methods for Globe Valves
A globe valve is a straight-line motion valve, mainly used for opening and closing fluid channels. In the pressure testing process of a globe valve, strength tests and sealing tests need to be carried out separately.
1. Globe Valve Strength Test
The purpose of the strength test is to detect the pressure resistance of the valve body and valve cover under high pressure, ensuring that the material strength is sufficient to withstand working pressure. The test steps are as follows.
Place the assembled globe valve on the test frame, open the valve disc to avoid forming a cavity pressure inside.
Introduce the test medium into the valve, gradually increase the pressure to the specified test value.
Under the specified pressure, carefully check the surface of the valve body and valve cover to ensure there is no leakage or sweating.
2. Globe Valve Sealing Test
The sealing test checks the sealing performance of the globe valve when closed. The steps are:
During testing, keep the valve stem vertical with the disc open.
Introduce the medium from below the valve disc to the specified pressure, checking the seals at the packing and gaskets. No leakage indicates a pass.
Then close the valve disc and open the other end to check for leaks at the valve seat.
If both strength and sealing tests are required, usually perform the strength test first, then reduce the pressure to the sealing test value and follow the above steps.
Pressure Testing Methods for Gate Valves
A gate valve is a valve with a gate as the closing part, mainly used to cut off the fluid. Its pressure testing method is similar to that of the globe valve, but the sealing test is slightly different.
1. Gate Valve Strength Test
The strength test method for gate valves is the same as that for globe valves. It detects the pressure resistance of the valve body and valve cover under high pressure conditions to ensure that the material performance meets the requirements.
2. Gate Valve Sealing Test
The sealing test for gate valves includes two main methods.
Intermediate Pressure Test
Open the gate to increase the internal pressure to the specified value, then close the gate and remove the valve. Check for leaks on both sides of the gate. This method is suitable for gate valves with a nominal diameter greater than DN32mm.
Repeated Testing Method
First, open the gate and increase the test pressure to the specified value. Then, close the gate, open one end’s blind flange, and check the sealing surface for leaks. Repeat this process until the valve passes.
Before conducting the sealing test for gate valves, a separate sealing test should be performed at the packing and gaskets to ensure good sealing.
Pressure Testing Methods for Plug Valves
A plug valve is a valve that regulates the flow of fluid by rotating the plug, suitable for occasions that require quick opening and closing and tight sealing.
1. Plug Valve Strength Test
The steps for the strength test of a plug valve are as follows:
Introduce the medium from one end and seal the other passages.
Rotate the plug to each fully open working position for testing, and check for leakage in the valve body. If there is no leakage, it is considered qualified.
2. Plug Valve Sealing Test
The sealing test for plug valves is divided into straight-through and multi-way types.
Straight-through Plug Valve Sealing Test
Maintain equal pressure between the chamber and passage, rotate the plug to the closed position, and check from the other end. Then rotate the plug 180° and repeat the test.
Multi-way Plug Valve Sealing Test
Maintain equal pressure between the chamber and one end of the passage, rotate the plug sequentially to each closed position, and introduce pressure from the right-angle end, checking all other ends simultaneously.
A thin layer of non-acidic dilute lubricant may be applied to the sealing surfaces before testing. The plug valve test duration is usually short, typically 1-3 minutes depending on the nominal diameter.
Pressure Testing Methods for Butterfly Valves
A butterfly valve is a valve that regulates the flow of fluid by rotating the valve plate, widely used for flow regulation and cutting off.
1. Butterfly Valve Strength Test
The strength test method for butterfly valves is the same as that for globe valves, mainly used to verify the pressure-bearing capacity of the valve body.
2. Butterfly Valve Sealing Test
The sealing test steps for butterfly valves are as follows:
Introduce the test medium from the inlet side of the butterfly valve with the disc open and seal the other end. Increase the pressure to the specified value.
After checking that there are no leaks at the packing and other seals, close the disc, open the other end, and check the disc seal for leaks.
Butterfly valves used for flow regulation may not require a sealing test.
Pressure Testing Methods for Check Valves
Check valves are tested for strength and sealing to ensure they can effectively prevent backflow while having sufficient pressure resistance during operation.
1. Check Valve Strength Test
The strength test checks whether the check valve body and bonnet can withstand the specified pressure without leaking or breaking. During testing, keep the swing check valve disc axis vertical and the swing check valve’s channel axis and disc axis approximately parallel to the horizontal. Introduce the test medium from the inlet and gradually increase the pressure to the specified test value. Maintain pressure for a period, usually 2 to 5 minutes, and observe whether the valve body and bonnet leak. If no leaks occur, the strength test passes.
2. Check Valve Sealing Test
The sealing test checks the check valve’s sealing performance when closed, ensuring it effectively stops backflow when the flow direction changes. Introduce the test medium from the outlet and gradually increase the pressure to the specified value. Observe the sealing surface, packing, and gaskets at the inlet for leaks. During the test, ensure the medium completely fills the valve chamber and maintains pressure for a period, typically 2 to 3 minutes. If no leaks or pressure drops are observed, the sealing test passes.
Valve pressure testing is an indispensable step in the manufacturing and usage of valves, ensuring safety and reliability under various conditions through rigorous strength and sealing tests. Choosing the appropriate testing method based on the valve type and application can effectively identify and resolve potential issues, extend the valve's service life, and ensure the safe operation of pipeline systems.
