Inspection | Pressure Reducing Valve Inspection Standards and Methods

1. Appearance quality inspection specifications

1. Surface integrity inspection

• Defect detection requirements:

  • Full surface visual inspection (light intensity ≥ 500 lux)

  • Use a 10x magnifying glass to check key areas

  • The following defects are prohibited:

    • Linear defect: crack length > 2mm

    • Area defects: pore/sand hole diameter>1.5mm

    • Dense defects: >3 defects per 100cm² area

• Surface treatment standards:

  • Non-machined surface roughness Ra≤12.5μm

  • Casting riser residual height <0.5mm

  • Anti-corrosion coating thickness 80-120μm (epoxy resin)

2. Dimensional accuracy verification

• Key dimensional tolerances:

  • Nominal diameter deviation: ±0.5mm below DN50, ±1% above DN50

  • Flange hole distance tolerance: ±0.3mm

  • Structural height deviation: ≤1% of nominal size

• Weight Control:

  • Casting weight tolerance: ±5% (relative to theoretical value)

  • Assembly weight records must retain traceability data

3. Identification system check

• Permanent marking on valve body:

  • Laser marking depth ≥0.3mm

  • Included elements: material brand, PN value, DN value, smelting batch number, flow direction arrow

  • Character height ≥5mm (DN≥50)

• Nameplate specifications:

  • 304 stainless steel substrate thickness ≥ 0.8mm

  • Etching content: working pressure range, medium temperature, factory serial number

  • The anti-counterfeiting QR code contains the complete product profile

2. Performance Testing Standard System

1. Voltage regulation characteristics test

• Test conditions:

  • Medium: Clean water or air (depending on the application scenario)

  • Inlet pressure: 1.25 times the nominal pressure

  • Test point: minimum/rated/maximum three-level outlet pressure

• Eligibility criteria:

  • Adjust linearity deviation <5% FS

  • Adjustment mechanism operating torque ≤ 50N·m

  • No sticking phenomenon (starting torque fluctuation <10%)

2. Dynamic characteristics test

• Flow rate mutation test:

  • When the step changes from 0.2Qmax to Qmax

  • Direct type: pressure overshoot <15%

  • Pilot type: recovery time < 3s

• Pressure disturbance test:

  • Inlet pressure ±10% step change

  • Outlet pressure fluctuation:

    • Direct type: Steady-state deviation <8%

    • Pilot type: Steady-state deviation <3%

3. Sealing performance grading test

• Low pressure seal (0.6MPa):

  • Bubble method detection: ≤12 bubbles/min (DN65-125)

  • Pressure test: 5min pressure drop < 0.02MPa

• High pressure seal (1.1×PN):

  • Metal seal: leakage rate <0.1%Qmax

  • Soft seal: zero visible leakage

4. Durability verification

• Accelerated life testing:

  • 100,000 pressure cycles (0.2PN→1.1PN)

  • 50,000 adjustment stroke tests

  • Performance degradation after the test is less than 5%

3. Material and process control

1. Key component inspection

• Valve body:

  • Radiographic inspection complies with ASME B16.34 Class B

  • Material spectrum analysis (PMI testing)

• Valve disc/seat:

  • Hardness test HRC35-45 (stainless steel)

  • Flatness ≤0.01mm

2. Assembly quality control

• Torque control:

  • Flange bolt preload deviation ±10%

  • Adjustment mechanism axial clearance <0.1mm

• Cleanliness:

  • NAS 1638 Class 6 (Hydraulic Systems)

  • Particle size ≤ 25 μm

4. Additional tests for special applications

1. Low temperature working conditions (-46℃)

• Material impact test: CVN ≥ 27J

• Cold sealing test (after LN2 immersion)

2. Corrosive environment

• Salt spray test: 1000h (ISO 9227)

• SCC stress corrosion assessment

3. Sanitary applications

• Surface roughness: Ra≤0.8μm

• Microbiological testing meets 3-A standards

5. Inspection Document System

1. Test report requirements

• Original data retention ≥ 10 years

• Calibration certificate traceability chain included

• Third-party witnessing of critical tests (such as blast tests)

2. Certification mark

• Compulsory certification: CE/PED/ASME, etc.

• Voluntary certification: API/UL/TÜV, etc.

3. Digital management

• Create product electronic resume

• Key parameter QR code traceability

• Big Data Analysis Quality Trends

Note: For pilot-operated pressure reducing valves, additional verification of the pilot valve response characteristics (step response time < 0.5s) is required. Ultra-high-pressure valves (PN > 420) should undergo full-scale burst testing in accordance with ASME B31.3. Manufacturers are advised to establish ANSYS simulation models and conduct virtual verification of new models before conducting physical testing.