How to Ensure the Safety of Dry-Type Valve Loading Arms for Diesel and Gasoline
I. Safety Design and Selection of Core Components
Safety Features of Dry-Type Valves
Zero-Leakage Mechanism: Adopts API-standard self-sealing structure. The valve core automatically closes during disconnection to prevent liquid or vapor leakage (e.g., the spring force of the valve core must be regularly calibrated to ensure the sealing surface pressure ≥ 0.5MPa).
Corrosion-Resistant Materials: Made of 316L stainless steel or Hastelloy to withstand chemical erosion from gasoline and diesel, preventing valve body perforation. (Materials must comply with NACE MR0175 for sulfide stress corrosion cracking resistance).
Pressure Relief Function: Equipped with a pressure relief valve (set at 1.2 times the working pressure) to prevent pipeline overpressure and rupture.
Protection for Swivel Joints and Pipeline System
Enhanced Sealing Structure: Uses double-lip PTFE seals + stainless steel retaining rings for wear and aging resistance (seal test pressure must reach 1.5 times the working pressure with no pressure drop after 30 minutes).
Anti-Fatigue Design: Pipeline welds must undergo 100% non-destructive testing (UT/RT). The outer arm rotating shaft sleeve uses self-lubricating bearings to reduce mechanical wear risks.
Configuration of Safety Protection Components
Breakaway Valve: Installed at the connection between the vertical pipe and outer arm. It automatically disengages when subjected to a tensile force of 500-800kg, preventing pipeline rupture and liquid spillage during emergency situations (re-engagement torque should be ≤ 30N·m for quick reset).
II. Safe Installation and Commissioning Standards
Installation Alignment Requirements
Verticality tolerance of the main pipeline: ≤ 2mm/m, ensured by laser leveling to prevent stress concentration at swivel joints.
Horizontal clearance between the loading arm and tank truck interface: maintained at 100-150mm to avoid collision during operation.
Grounding and Static Control
Equip conductive braided wires (cross-sectional area ≥ 6mm²) at each swivel joint, with the entire system grounding resistance ≤ 10Ω (tested quarterly using a grounding resistance meter).
Install static eliminators at the liquid outlet, reducing static potential to < 100V during loading.
III. Operational Safety Protocols
Pre-Operation Inspections
Check for visible damage (e.g., cracked seals, loose fasteners) and test the dry-type valve's self-sealing function with a manual lever before each use.
Verify that the balance system (spring cylinder/counterweight) allows the outer arm to float freely without (sticking).
Loading Process Controls
Limit the initial loading velocity to ≤ 1m/s, gradually increasing to ≤ 4.5m/s after the liquid covers the vertical pipe outlet to prevent static accumulation.
Implement interlocking systems: the dry-type valve cannot be opened unless the quick connector is fully locked (verified by proximity switches).
IV. Regular Maintenance and Safety Testing
Preventive Maintenance Schedule
Seal replacement: Conduct annually to replace PTFE seals, ensuring they show no signs of aging or cracking.
Spring force calibration of dry-type valve: Perform biannually to maintain the force within 0.5-0.8MPa, ensuring the self-sealing mechanism functions correctly.
Breakaway valve tensile test: Carry out triennially to verify that the valve disengages at a tensile force of 500-800kg, as specified.
Leakage Testing
Soap bubble test: Annually apply a test pressure of 1.1 times the working pressure to all joints, checking for bubbles; no bubbles should appear within 5 minutes.
Infrared gas detection: Use an infrared detector to monitor vapor emissions around the loading arm, ensuring the concentration remains below 1000ppm.
V. Emergency Response and Safety Devices
Fire and Explosion Prevention
Install flame arresters at the gas phase pipe outlet, with a fire resistance rating meeting API 2000 standards.
Equip emergency shutdown systems (ESD) that can cut off the liquid supply within 10 seconds of a flame or gas leak alarm.
Personnel Protection Measures
Require operators to wear anti-static clothing and grounding wrist straps, with all tools made of non-sparking materials (e.g., copper alloy).
Design operation platforms with guardrails (height ≥ 1.2m) and anti-slip surfaces to prevent falls.
Key Safety Indicators
Leakage rate: ≤ 0.1L/h at any joint under working pressure.
Static potential: ≤ 500V during the entire loading process.
Response time for emergency shutdown: ≤ 15 seconds from alarm activation.
