What should be noted in cutting and bending?
It is recommended to use a band saw (low speed) or laser cutting for cutting to avoid hardening of the pipe end by the grinding wheel. The minimum bending radius during cold bending is ≥3 times the outer diameter (≥5 times for stainless steel) to prevent wrinkling. The bending mold needs to be polished and coated with lubricant (such as molybdenum disulfide) to reduce scratches. For thick-walled pipes (＞6mm), hot bending (heating to 600-800℃) and controlled cooling rate are recommended. After bending, roundness detection (ovality ≤5%) is required, and correction with a mandrel is required if necessary.
How to avoid deformation when welding precision pipes?
TIG welding (tungsten inert gas shielded welding) is preferred, with a small heat-affected zone and no spatter. Liner rings (fusible type) are required for butt welding to ensure the flatness of the inner wall. Before welding, the groove needs to be cleaned (acetone degreasing) and the fixture is fixed (spacing ≤300mm) to control shrinkage. The segmented back welding method (50-80mm per segment) is used to disperse heat. After welding, stress relief annealing is required (such as heating stainless steel pipes to 550℃), and finally the weld quality is checked with an endoscope.
How to clean the hydraulic system pipeline?
Before installing the new pipe, it needs to be circulated and pickled with 20% nitric acid + 3% hydrofluoric acid solution for 2 hours to remove the oxide scale. Flushing uses high-pressure oil (≥40℃) until the particle size meets the standard (NAS 1638 Class 6). Pipeline assembly must be carried out in a clean room, and the interface is sealed with a plastic cap. A temporary filter (β≥200) should be installed during the system trial operation, and the filter element should be replaced regularly. Long-term shutdown requires nitrogen protection to prevent condensation water corrosion.
Anti-corrosion measures during long-term shutdown?
The inner wall of the carbon steel pipe can be coated with anti-rust oil (such as MIL-PRF-16173E Grade 2), and the outer wall is covered with VCI anti-rust film. Stainless steel pipes need to be kept dry (humidity ≤40%) to avoid chloride ion accumulation. It is recommended that the pipeline system be filled with dry air (dew point ≤ -40℃) or inert gas (such as argon). Check the surface condition every 3 months, and the cycle needs to be shortened in coastal areas. Wipe with alcohol and perform pressure test before reactivation.
Quick diagnosis tips for leakage failure?
External leakage can be located by fluorescent penetrant (UV light detection). Internal leakage requires segmented pressure maintenance test (pressurized to 1.5 times the working pressure), and hissing sound is identified with a stethoscope. Hydraulic system should first check the pipe joints (accounting for 70% of the failure rate) to confirm whether the sealing ring is aged. Microporous leakage can be observed by applying soapy water. For fatigue cracks caused by vibration, it is necessary to check whether the support spacing is too large (recommended ≤1.5m) and add shock-absorbing rubber pads.
