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Sealing Test Method for Dual Plate Check Valves

8

January

The sealing test of dual plate check valves can follow the three-core process of “Visual Inspection — Static Test —…

The sealing test of dual plate check valves can follow the three-core process of “Visual Inspection — Static Test — Dynamic Test” to verify the valve’s sealing performance step by step; professional testing can be supplemented for high-demand scenarios, while relevant test specifications and safety requirements must be strictly followed. The specific test methods are as follows:

I. Visual Inspection (Basic Screening)

  • Valve Body and Bonnet: Focus on checking the tightness of the connecting parts, and inspect the valve body and bonnet for structural defects such as sand holes, air holes, and cracks to ensure that the basic components have no damage affecting the seal.
  • Sealing Surface: Observe the contact surface between the valve core and the valve seat, which should be smooth and flat without damage such as wear, scratches, corrosion, or deformation; if there are slight scratches, it is necessary to evaluate whether they affect the sealing fit.
  • Sealing Material: Inspect according to the seal type — for soft-sealed valves, confirm that the sealing material has no aging, cracking, or peeling; for hard-sealed valves, verify that the hardness of the sealing surface meets the design and relevant standard requirements.

II. Static Test (Sealing Verification Without Working Conditions)

(I) Hydraulic Test
  1. Close the valve, connect a pressure water source that meets the test requirements to one end of the valve, and seal the other end with a sealing device to ensure no additional leakage points in the test circuit.
  2. Slowly raise the pressure to 1.5 times the nominal pressure of the valve and maintain the pressure for 15-30 minutes (the specific pressure holding time can be adjusted according to the valve diameter, and can be appropriately extended for large-diameter valves).
  3. Observation Points: Continuously check whether there is leakage on the valve body surface, valve stem stuffing box and other key parts; if there is no obvious pressure drop during the test and no leakage traces, it indicates that the static hydraulic sealing performance is good.

(II) Pneumatic Test

  1. Applicable Scenarios: Suitable for valves not suitable for hydraulic testing (such as valves afraid of water corrosion, low-temperature working condition valves) or precision working conditions with strict requirements on leakage.
  2. Test Process: Fill the valve with dry inert gas such as nitrogen (to avoid oxidative corrosion), apply soapy water to the sealing parts, or use professional leakage detection equipment for testing.
  3. Judgment Standard: If no bubbles are generated at the parts where soapy water is applied, or the professional detection equipment does not display leakage signals, it indicates that the static pneumatic sealing performance is qualified.

III. Dynamic Test (Sealing Verification Under Actual Working Conditions)

(I) Valve Opening and Closing Test
  1. Operation Method: Complete the valve opening and closing actions through manual, electric, pneumatic or other driving methods in multiple cycles (it is recommended that the number of cycles is not less than 5 to simulate the actual service frequency).
  2. Observation Points: First, check whether the valve opening and closing process is smooth, and whether there are jamming, abnormal noise or abnormal increase in resistance; second, after each closing, apply leak detector to the sealing parts or observe whether there is medium seepage.
  3. Judgment Standard: The opening and closing actions are smooth, and there is no leakage after each closing, indicating stable dynamic sealing performance.

(II) Flow Test

  1. Test Environment: Install the valve in the actual pipeline system or build a test circuit simulating actual working conditions.
  2. Test Process: Measure the medium flow rate of the valve at different openings, focusing on verifying the flow data in the fully closed state.
  3. Judgment Standard: When the valve is fully closed, the flow rate should be close to zero; if there is still obvious flow passing through, it indicates internal leakage and the sealing performance is not up to standard.

IV. Professional Testing (Supplementary for High-Demand Scenarios)

(I) Ultrasonic Testing
Use ultrasonic testing equipment to capture changes in ultrasonic signals generated by leakage at the valve sealing parts; accurately determine the leakage location and degree through signal analysis, which is suitable for micro-leakage that is difficult to detect by conventional testing.
(II) Helium Mass Spectrometry Testing
Applicable Scenarios: Mainly used in special working conditions extremely sensitive to micro-leakage such as high-vacuum systems, nuclear industry, and aerospace.
Test Principle: Place the valve in a sealed environment filled with helium, or fill the valve with helium, and use a helium mass spectrometer to detect whether there is helium leakage outside the valve or in the surrounding environment; helium molecules are small in size, which can accurately detect micro-leakage.

V. General Precautions

  • Selection of Test Medium: Should be selected according to the actual working medium type of the valve. Common test media include water, industrial oil, dry air, steam, nitrogen, etc., to avoid chemical reactions between the test medium and the valve material.
  • Test Pressure Control: The strength test pressure is usually 1.5 times the nominal pressure, and the sealing test pressure is generally not lower than the nominal pressure; overpressure testing is strictly prohibited to prevent damage to valve components.
  • Safety Protection Measures: Set up safety protection barriers during the test, and operators must wear protective equipment; during high-pressure testing, it is strictly prohibited to stand directly facing the valve sealing surface or connecting parts to avoid personal injury caused by high-pressure medium leakage.
  • Retention of Test Records: Detailedly record test time, test medium, test pressure, pressure holding time, test results and other data to form a complete test report, which is convenient for subsequent tracing and quality control.