What are the requirements and methods for pressure testing of imported valves?

In general, industrial valves are not subjected to strength tests during use; however, strength tests should be performed on valve bo and bonnets after repair, or on those damaged by corrosion. For safety valves, their set pressure, reseating pressure, and other tests must comply with the specifications in the instructioand relevant regulations. Before installation, valves should undergo strength and seal tests. For low-pressure valves, a random check of 20% is conducted; if ny fail, 100% inspection is required. For medium and high-pressure valves, 100% inspection is mandatory. Common media used for valve pressure testing include water, oil air, steam, and nitrogen.

This article will analyze issues related to valve pressure testing by combining the standard requirements and procedures of the renowned imported valve brand, German LIT Valves.

I. irements for Imported Valve Pressure Testing:

1. Every valve must undergo pressure testing before leaving the factory. The renowned imported valve brand German LIT strictly adheres to this standar. Before the shell test is completed, it is not allowed to paint the valve or apply other coatings to prevent leakage; however, chemical rust prevention treatments without sealing effects and linings for d valves are permitted. For valves in inventory that have already been painted, if the user representative requests a retest, the coating does not need to be removed.

3. Befhe seal test, oil stains on the sealing surface should be removed; however, a thin layer of protective agent with a viscosity no greater than kerosene is allowed. For valves seald by grease, the grease specified by the design is permitted.

4. During the test, the valve should not be subjected to external forces that may affect the test results.

5. Unless otherwie specified, the temperature of the test medium should be between 5~40℃. However, for valves required to meet high-temperature medium operating conditions, the medium can  be used for seal testing.

6. The following test media are selected by the manufacturer but must comply with the provisions of Table 1 and Table 2: a) Liqu water (with rust inhibitor added), kerosene, or other suitable liquids with a viscosity no greater than kerosene; b) Gases: air or other suitable ga. When using a liquid for testing, the gas inside the valve cavity should be purged. When using a gas for testing, safety precautions must be taken.

8. During seal anr seal tests, the valve should be closed in the manner specified by the design.

9. The test pressure must comply with the 

II. Methods and Procedures for Import Valve Pressure Testing

Shell tests and upper seal tests shall be performed first, followed by sests.

Upper Seal Test

Close the valve inlet and outlet. Loosen the gland (if the valve is equipped with an upper seal inspection device and the upper seal performance can be reliably chewithout loosening the gland, the gland need not be loosened). Keep the valve in the fully open position and close the upper seal. Fill the body cavity with test medium and graduaincrease the pressure to the test pressure, then check the upper seal performance.

2. Shell Test

Close the valve inlet and outlet. Tighten the gland to maintain the test pre, and keep the closing member in a partially open state. Fill the body cavity with test medium and gradually increase the pressure to the test pressure (for check valves, pressure shall be applom the inlet end), then inspect the shell (including the packing box and the connection between the valve body and bonnet).

III. Understanding of Relevant Pressure Testing Terms

Test pressurdivided into shell test pressure and seal test pressure. The pressure specified for valve shell testing is called the excess pressure test pressure. The pressure specified for valve seal testing is called the seal t pressure.

The "Valve Testing and Inspection" standard stipulates:

1. Shell test pressure is 1.5 times the nominal pressure at 38°C. For , for German LIT import ball valves with a nominal pressure of 1.6 MPa, the shell test pressure is 2.4 MPa; for import globe valves winal pressure of 2.5 MPa, the shell test pressure is 3.75 MPa.

2. High-pressure seal test and high-pressure upper seal test pessure is 1.1 times the nominal pressure at 38°C. For example, for German LIT import gate valves and import solenoid valves with a nominal prere of 1.6 MPa, the high-pressure seal test and high-pressure upper seal test pressure is 1.76 MPa.

3. Low-pressure seal test and low-pressure upper seal t pressure is 0.5~0.7 MPa.

4. Butterfly valve seal test pressure is 1.1 times the rated pressure difference.

5. Check valve seal t pressure is the nominal pressure at 38°C.