1. Purpose of Pressure Test
The fundamental purpose of pressure testing is to verify the integrity and sealing performance of the valve, ensuring that it will not leak or fail under operating conditions. It mainly includes shell strength testing and sealing performance testing.
Strength testing: Verifies whether pressure-bearing components such as the valve body and valve cover can withstand the operating pressure without deformation or damage.
Sealing testing: Verifies whether the valve's closing components (such as the valve seat and valve disc) and sealing structures (such as the stuffing box) can effectively prevent media leakage under operating pressure.
2. Main Test Types and Methods
2.1 Shell strength test：
Objective: To test the strength and tightness of fixed components such as valve body and valve cover.
Methods
1) Position the valve half-open.
2) Fill the valve cavity with pressurized liquid (usually water) to purge air.
3) Slowly increase the pressure to the specified test pressure (usually 1.5 times the nominal pressure).
4) Maintain the pressure for a period of time.
|
Minimum Holding Time for Strength Test |
|
|
Nominal Diameter（DN）/mm |
Minimum Holding Time/s |
|
≤50 |
15 |
|
65~200 |
60 |
|
≥250 |
180 |
Acceptance criteria: No visible leakage, dripping, or deformation in any part of the valve body (especially at the thinnest part of the wall).
2.2 Sealing test
Objective: To test the sealing performance of the valve in the closed state, including the valve seat seal and the valve stem packing seal.
2.2.1Top sealing test
Applicable to valves with a top sealing structure—gate valves, globe valves, etc.:
1) Fully open the valve and tighten the top sealing seat.
2) Pressurize the valve cavity and check for leaks at the valve stem packing.
2.2.2Low-pressure sealing test & High-pressure sealing test：
The valve is in the fully closed position.
Introduce the test medium into one end of the valve and check for leaks from the other end. Typically, both ends of the valve need to be tested separately.
Sealing Test Pressure：
|
Nominal Diameter（DN）/mm |
Nominal Pressure（PN）/MPa |
Test Pressure |
|
≤50 |
≤5.0 |
a) Hydraulic test: 1.1 times the valve's maximum working pressure at 20℃; or 1.1 times the valve's nominal pressure. b) Pneumatic test: 0.5~0.7MPa |
|
≥65 |
All Pressure Values |
Hydraulic test: 1.1 times the valve's maximum working pressure at 20℃; or 1.1 times the valve's nominal pressure. |
Test Time：
|
Nominal Diameter（DN）/mm |
Minimum Test Time/S |
|
|
Valves with Metal seat |
Valves with flexible valve seats or valve seats made of polymer materials |
|
|
≤50 |
15 |
15 |
|
65~200 |
30 |
|
|
250~450 |
60 |
30 |
|
≥500 |
120 |
60 |
Acceptance criteria: Sealing performance includes the sealing performance of the valve seat sealing surface, valve disc sealing surface, valve body flange sealing surface, and valve cover packing cavity sealing surface. Except for swing check valves, plug valves, and valve cover packing cavity sealing surfaces, which are allowed to have a leakage of (0.01*DN) mm³/s during liquid testing, there should be no visible leakage in any of the other types of valves.
Test Media:
Liquid: Can be fresh water, water containing preservatives, kerosene, or other suitable liquids with a viscosity no greater than water.
Gas: Usually air or an inert gas (such as nitrogen) is used. It has low pressure (e.g., 0.5-0.7 MPa), high sensitivity, and is used to detect extremely small leaks; when selecting a gas as the test media, the manufacturer should have strict safety measures in place.
Test Medium Temperature: Unless otherwise specified, the temperature of the test medium should be between 5°C and 40°C.
Standards and Specifications to be Followed: Pressure testing of marine valves must strictly comply with international, national, and classification society standards.
Internationally Recognized Standards: GB/T600, API 598, MSS SP-61: These are authoritative standards for valve inspection and testing and are widely cited.
Major Classification Society Specifications: Standards such as ABS, DNV, LR, BV, and CCS all have requirements for valve testing.
Test Execution and Documentation
1）Factory Testing: Every valve must undergo testing before leaving the factory.
2）Testing Equipment: A professional pressure testing bench capable of precisely controlling pressure and holding time.
3）Test Report: The report should include at least the following information:
4）Valve model and serial number
5）Nominal diameter and pressure rating
6）Test medium, test pressure, and holding time
7）Test results (pass/fail)
8）Test date
9）Signatures/stamps of the operator and inspector, etc.