I. main Parameters of Two Pressure Specifications
The core differences between the two pressure specifications of valves are concentrated in torque requirements, material thickness and sealing standards. The specific parameters are as follows (accurately adapted to installation and leakage judgment):
1. 1500psi (10.34MPa): Suitable for DN10-DN25 pipelines, ferrule thickness 1.2-1.5mm, recommended tightening torque 25-55N·m (25N·m for DN10, 55N·m for DN25), required seal leakage rate ≤1×10⁻⁶ mbar·L/s, applicable medium pressure ≤10.34MPa, temperature -20℃~200℃.
2. 3000PSI (20.68MPa): Suitable for DN10-DN20 pipelines, ferrule thickness 1.8-2.2mm, recommended tightening torque 45-80N·m (45N·m for DN10, 80N·m for DN20), required seal leakage rate ≤1×10⁻⁹ mbar·L/s, applicable medium pressure ≤20.68MPa, temperature -40℃~250℃.
Key Reminder: Due to the higher pressure of 3000PSI valves, the ferrule material must be 2205 duplex stainless steel (PREN≥35), which has 50% higher corrosion resistance than 316L stainless steel used for 1500psi, avoiding corrosion and leakage under high pressure.
II. Simplified Installation Process
Installation Core: The higher the pressure, the stricter the requirements for torque control and pipeline preprocessing. The following process only retains key steps, adapted to both specifications with data.
1. Pipeline Preprocessing
Cutting: The perpendicularity error of the pipe end shall be ≤0.5°, without burrs (if the inclination exceeds 0.5°, the leakage risk increases by 30% for 1500psi and 60% for 3000PSI); Cleaning: After ultrasonic cleaning, purge with high-pressure nitrogen to ISO 14644-1 Class 5. Impurity residue will cause ferrule scratches, increasing the leakage probability by 45%.
2. Ferrule Assembly and Torque Control
Assembly: Put the nut, front ferrule and rear ferrule into the pipeline in sequence, with the ferrule cutting edge facing the fitting body. Reversing the ferrule will directly cause leakage (the maintenance cost is about 500 yuan/time for 1500psi and 1200 yuan/time for 3000PSI).
Torque Control (Core Data):
1500psi: Tighten in two stages - first stage: tighten the nut clockwise to 70% of the standard torque (e.g., 38.5N·m for DN15), second stage: continue tightening to the torque sudden increase point (pressure point), then rotate an additional 1/4 turn. The torque error shall be ≤±5% (excessive error will cause ferrule deformation, with a leakage rate of 12%).
3000PSI: Tighten in two stages - first stage: tighten the nut clockwise to 70% of the standard torque (e.g., 63N·m for DN15), second stage: continue tightening to the torque sudden increase point (pressure point), then rotate an additional 1/2 turn. The torque error shall be ≤±3% (excessive error will cause ferrule fracture, with a leakage rate of 28%).
3. Seal Verification
1500psi: For liquid medium, apply 1.5 times the working pressure (15.51MPa) for hydrostatic test, hold pressure for 30 minutes, and pressure drop ≤0.05MPa is qualified; For gas medium, use a helium mass spectrometer leak detector with a sensitivity of 1×10⁻⁶ Pa·m³/s.
3000PSI: For liquid medium, apply 1.5 times the working pressure (31.02MPa) for hydrostatic test, hold pressure for 30 minutes, and pressure drop ≤0.03MPa is qualified; For gas medium, the leak detection sensitivity is 1×10⁻⁹ Pa·m³/s to avoid micro-leakage under high pressure.
III. Common Leakage Problems, Causes and Solutions
Leakage fault proportion of the two pressure specifications: For 1500psi, the main causes are improper torque (40%) and reversed ferrule assembly (25%); For 3000PSI, the main causes are substandard materials (35%) and excessive torque error (30%). The specific solutions are as follows:
1. External Leakage
Fault Phenomenon: Liquid/gas seeps at the connection between the valve and the pipeline, and the leakage becomes more obvious as the pressure increases.
Common Causes and Data:
(1) Insufficient/Excessive Torque: For 1500psi, if the torque is 10% lower than the standard value, the leakage rate reaches 18%; For 3000PSI, if the torque is 10% higher than the standard value, the ferrule deformation leakage rate reaches 32%.
(2) Reversed Ferrule Assembly: Under both pressures, the leakage rate is 100% after reversal, and ferrule fracture may occur in 3000PSI scenarios.
(3) Pipeline Wall Damage: If the pipe diameter deviation is ＞0.1mm, the leakage rate is 22% for 1500psi and 45% for 3000PSI.
Solutions:
1500psi: Re-tighten the nut to the standard torque. If the ferrule is deformed (visible depression to the naked eye), replace the ferrule (single cost is about 80 yuan); If the pipeline wall is damaged, replace the pipeline, and control the deviation within 0.1mm.
3000PSI: Calibrate the torque with a digital torque wrench, and control the deviation within ±3%; If the ferrule is installed reversely, replace the ferrule (single cost is about 180 yuan); If the pipeline wall is damaged, replace it with a thickened pipeline (thickness ≥2.0mm).
2. Internal Leakage (Accounting for 20%)
Fault Phenomenon: After the valve is closed, the medium still circulates, and a flow rate ＞0.01L/min is regarded as leakage.
Common Causes and Data:
(1) Valve Seat Scratch: For 1500psi, if the scratch depth is ＞0.03mm, the leakage rate is 15%; For 3000PSI, if the scratch depth is ＞0.02mm, the leakage rate is 30%.
(2) Seal Ring Aging: For 1500psi, if the seal ring is used for more than 18 months, the aging leakage rate is 20%; For 3000PSI, if used for more than 12 months, the aging leakage rate is 40%.
Solutions:
1500psi: Grind the valve seat (the roughness after grinding Ra≤0.4μm), or replace the seal ring (PTFE material, which can be used continuously if the compression loss is ≤20%).
3000PSI: Replace the valve seat (overlay welding Stellite 6 alloy with hardness HRC 45), select high-temperature and high-pressure resistant seal rings (capable of withstanding 250℃ and 31MPa), and replace them every 12 months.
3. Special Leakage Under High Pressure Conditions (3000PSI Only)
Fault Phenomenon: When the system pressure rises above 18MPa, sudden leakage occurs at the joint, mostly accompanied by ferrule loosening.
Cause: Insufficient ferrule thickness (＜1.8mm) or inconsistent material (failure to use 2205 duplex stainless steel), leading to deformation due to stress concentration under high pressure.
Solution: Replace with 2.0-2.2mm thick 2205 duplex stainless steel ferrule, re-assemble according to the standard torque, and the pressure drop during verification shall be ≤0.03MPa, which can avoid such leakage (the leakage rate drops to below 0.5% after solution).
IV. Remark notes
1. Torque Control: Use an ordinary digital torque wrench for 1500psi; a high-precision torque wrench (error ≤±1%) must be used for 3000PSI to avoid torque deviation.
2. Maintenance Cycle: For 1500psi, check the torque every 3 months and replace the seal ring every year; for 3000PSI, check every 2 months and replace the seal ring every 6 months.
3. Medium Limitation: Under both pressures, the chloride ion content must be ≤25ppm; for 3000PSI scenarios, additional vacuum dehydrogenation treatment (for hydrogen medium) is required to reduce the leakage risk.
Summary: The key to installing 1500psi valves is to control torque error. Leakage is mostly caused by improper operation with low solution cost; 3000PSI valves need to control material, torque and pipeline accuracy simultaneously. The leakage risk is higher under high pressure, so parameter standards must be strictly followed.
