Testing of reducers shall cover four core aspects: dimensional accuracy, material compliance, structural integrity, and pressure resistance performance. Different testing items correspond to different methods, and testing priorities shall be adjusted according to the material (metal/plastic) and pressure rating (high pressure/low pressure).
I. Material Testing: Ensuring Material Compliance
1. Chemical Composition Testing
- Testing methods: Spectrometer (portable/benchtop), X-ray Fluorescence Spectrometer (XRF)
- Testing content: Verify the content of elements such as carbon (C), chromium (Cr), nickel (Ni), molybdenum (Mo) to meet grade requirements (e.g., 20# steel, 304 stainless steel, PE100)
- Application scenario: Random inspection of each batch of raw materials to prevent material mixing (e.g., carbon steel counterfeited as stainless steel)
2. Mechanical Property Testing (for Metal Reducers)
- Testing methods: Tensile test, hardness test
- Testing content:
- Tensile test: Sampling to test tensile strength and yield strength (e.g., tensile strength of 20# steel ≥ 415 MPa)
- Hardness test: Measured by Brinell hardness tester (HB); carbon steel ≤ 180 HB, stainless steel ≤ 200 HB
- Application scenario: Random inspection of 1 piece per batch for high-pressure reducers (PN ≥ 10 MPa)
II. Pressure Resistance Testing: Verifying Service Safety
1. Hydrostatic Test (Core Testing Item)
- Testing equipment: Hydrostatic testing machine, pressure gauge (accuracy ≥ 0.4 class)
- Testing procedure:
- Plug both ends of the reducer, fill with water and exhaust air completely
- Pressurize slowly to the test pressure (1.5 times the design pressure) and hold for 30 minutes
- Inspect for no leakage and no deformation (no obvious plastic deformation for metal reducers, no rupture for plastic reducers)
- Acceptance criteria: No pressure drop, no leakage, and no visible deformation during pressure holding
2. Pneumatic Tightness Test (for Reducers in Gas/Vacuum Pipelines)
- Testing equipment: Pneumatic tightness tester, soap solution
- Testing procedure:
- Charge compressed air (or nitrogen) to the test pressure (1.15 times the design pressure)
- Hold pressure for 24 hours and apply soap solution to inspect joints/welds
- Acceptance criteria: Pressure drop ≤ 1% and no bubble formation
3. Burst Test (Type Test)
- Testing method: Increase pressure gradually until the reducer ruptures and record the burst pressure
- Acceptance criteria: Burst pressure ≥ 2.5 times the design pressure
- Application scenario: Product finalization and batch random inspection (1 piece per 1000 pieces)
III. Special Testing: Adapting to Scenario Requirements
1. Wear Resistance Testing (for Reducers in Slurry/Particle-Containing Fluid Pipelines)
- Testing method: Wear test bench (simulating particle erosion)
- Testing content: Measure wear rate and verify adhesion of wear-resistant layer (e.g., ceramic lining)
- Acceptance criteria: Wear rate ≤ 0.1 mm/1000 hours
2. Aging Testing (for Plastic Reducers)
- Testing methods: Thermal aging test (100 ℃, 168 hours), ultraviolet aging test
- Testing content: Measure retention rate of tensile strength and elongation at break after aging
- Acceptance criteria: Performance retention rate ≥ 80%
3. Soil Corrosion Testing (for Buried Reducers)
- Testing method: Soil corrosion test (simulating buried environment)
- Testing content: Measure corrosion rate and verify adhesion of anti-corrosion coating (e.g., PE coating)
- Acceptance criteria: Corrosion rate ≤ 0.01 mm/year
IV. Testing Procedure and Sampling Rules
Sampling Rules
- Mass production: 5% random inspection per batch (minimum 3 pieces), 100% inspection of critical dimensions
- High-pressure reducers: 100% hydrostatic test + 20% non-destructive testing
- Plastic reducers: 10 pieces random inspection per batch for pressure resistance test
Acceptance Judgment
- A batch is accepted if all sampled items are qualified
- If 1 piece is unqualified, double the sampling quantity for re-inspection; the batch shall be rejected if still unqualified
V. Common Testing Misconceptions
- Only appearance inspection is performed while wall thickness/material testing is ignored → leading to insufficient pressure resistance of thin-walled reducers
- Air is not completely exhausted during hydrostatic test → false high pressure leading to misjudgment of qualification
- No intergranular corrosion testing for stainless steel reducers → prone to corrosion failure in chemical media
