Quality Control & Testing Procedure Information Product Category: Pressure Relief & Pressure Control Valves

Quality Control and Testing Procedures for Pressure Relief and Pressure Control Valves

Pressure relief and control valves are critical for ensuring the safety and efficiency of systems by regulating pressure and preventing overpressure conditions. The following quality control (QC) and testing procedures ensure these valves meet performance, reliability, and compliance standards.

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1. Material Inspection

• Objective: Ensure all materials meet specified requirements for durability, compatibility, and performance.
• Procedure:
  • Review material test reports (MTRs) for components such as valve bodies, springs, diaphragms, and seats.
  • Conduct chemical composition analysis for metallic components (e.g., cast steel, stainless steel) to ensure compliance with ASTM, EN, or IS standards.
  • Test non-metallic materials (e.g., elastomers, polymers) for temperature and chemical compatibility.

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2. Dimensional Verification

• Objective: Confirm that all components meet design specifications and tolerances.
• Procedure:
  • Measure critical dimensions (e.g., orifice diameter, seat surface, spring length) using precision tools like micrometers, calipers, and CMM machines.
  • Verify flange dimensions and thread specifications conform to standards such as ASME B16.5 or ISO 7-1.

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3. Visual and Surface Inspection

• Objective: Detect surface defects and imperfections.
• Procedure:
  • Inspect all components for surface defects such as cracks, porosity, or rough finishes.
  • Use dye penetrant testing (DPT) or magnetic particle testing (MPT) for defect detection in critical components.

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4. Functional Testing

• Objective: Verify operational performance under simulated working conditions.
• Procedure:
  • Apply set pressure to confirm the valve opens at the specified pressure (pop-off or cracking pressure).
  • Monitor reseating pressure to ensure the valve closes properly after pressure normalization.
  • Test repeatability by cycling the valve multiple times.

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5. Leak Testing

• Objective: Ensure leak-tight performance under operating conditions.
• Procedure:
  • Perform seat leakage tests as per API 527 or equivalent standards.
  • Conduct hydrostatic and pneumatic pressure testing on valve bodies.
  • Submerge the valve under water or use a soap solution to identify leaks visually.
  • Ensure the valve meets allowable leakage rates for soft and metal-seated designs.

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6. Pressure and Flow Testing

• Objective: Verify valve performance under various pressure and flow conditions.
• Procedure:
  • Test the valve at maximum working pressure and flow rates using calibrated equipment.
  • Confirm the flow capacity aligns with manufacturer-specified Cv or Kv values.
  • Perform backpressure testing for pressure relief valves to ensure they operate correctly under backpressure conditions.

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7. Spring Testing

• Objective: Ensure the spring operates within specified load and compression ranges.
• Procedure:
  • Use a spring tester to measure the force at various compressions.
  • Verify spring compliance with design specifications for set pressure ranges.

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8. Environmental and Durability Testing

• Objective: Validate the valve’s performance in various environmental conditions.
• Procedure:
  • Conduct temperature cycling tests to simulate extreme operating temperatures.
  • Perform corrosion resistance testing (e.g., salt spray test per ASTM B117) for external components.
  • Conduct vibration and shock resistance testing as per IEC or equivalent standards.

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9. Seat and Seal Integrity Testing

• Objective: Ensure seals and seats prevent leaks under pressure.
• Procedure:
  • Inspect soft seats for deformation or wear after testing.
  • Perform bubble-tight leak tests for soft-seated valves using inert gases such as nitrogen or air.
  • Test metal-seated valves for allowable leakage rates as per API 598 or equivalent.

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10. Overpressure and Setpoint Testing

• Objective: Verify the valve’s ability to withstand and relieve overpressure safely.
• Procedure:
  • Gradually increase pressure in a controlled environment to verify set pressure (cracking pressure).
  • Monitor the valve’s behavior when exposed to overpressure conditions (e.g., 10% above set pressure for relief valves).
  • Ensure the valve reseats and closes within specified tolerances.

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11. Final Inspection

• Objective: Ensure the valve meets all quality standards before dispatch.
• Procedure:
  • Conduct a comprehensive visual and functional review.
  • Verify labeling, markings (e.g., pressure ratings, flow direction), and traceability information (e.g., serial numbers, material codes).
  • Ensure proper packaging to prevent damage during transportation.

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12. Documentation and Certification

• Objective: Provide customers with detailed quality assurance documentation.
• Procedure:
  • Prepare inspection and test reports, including material certificates, calibration results, and performance data.
  • Provide pressure test certificates and compliance documentation (e.g., ASME, API, ISO certifications).
  • Include operation and maintenance manuals with product delivery.

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Standards and Guidelines

• ASME Section VIII Division 1: Pressure relief device design and testing standards.
• API 526: Design and selection of pressure relief valves.
• API 527: Seat leakage testing for pressure relief valves.
• ISO 4126: Safety devices for protection against excessive pressure.
• ASTM B117: Salt spray corrosion testing.
• IEC 60068: Environmental testing standards for vibration and shock.

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Key Considerations

• Calibration and Certification: Use calibrated equipment for all tests and ensure certification traceability.
• Customization: Adjust QC and testing protocols to meet specific customer or application requirements.
• Continuous Improvement: Incorporate feedback and performance data into quality processes to enhance reliability.

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