The installation of low-temperature trunnion ball valves must adhere strictly to operational specifications to ensure sealing integrity, mechanical stability, and service life in cryogenic environments. Below is a detailed breakdown of critical installation considerations:
1. Pre-Installation Preparation
Material and Service Condition Verification
Confirm that valve materials (e.g., LCB/LC3 low-temperature steel for bodies, PTFE or metal seals for seats) are compatible with cryogenic media (e.g., LNG, liquid oxygen) and rated for the specified pressure/temperature range (typically -46°C to -196°C).
Validate compliance with standards (e.g., ASME B16.34, API 6D) by reviewing test reports, including low-temperature impact testing and pressure testing results.
Cleaning and Protection
Thoroughly clean the valve interior, sealing surfaces, and pipeline to remove contaminants (oil, welding slag, rust) that could damage seals or obstruct flow.
Protect threaded and flanged connections from impact or corrosion during storage and transportation.
2. Installation Location and Orientation
Positioning Requirements
Install in accessible locations to facilitate operation, maintenance, and inspection; avoid confined spaces or pipeline dead-ends.
For vertical installations, ensure the stem is oriented upward; for horizontal setups, maintain stem mobility to prevent uneven sealing surface loading due to gravity.
Flow Direction and Body Markings
Align the valve with the pipeline according to the arrow marking on the 阀体 (valve body) to ensure correct media flow. While most low-temperature ball valves are bidirectional, single-seat designs may have specific flow requirements-always reference the manual.
3. Connection Methods and Tightening Protocols
Flange Connections
Use gaskets matched to the valve's flange rating (e.g., CL150, CL300). In low-temperature applications, specify metal wound or expanded PTFE (ePTFE) gaskets to avoid rubber gasket embrittlement.
Tighten bolts symmetrically in 2–3 stages to ensure uniform flange loading and prevent leakage. Use low-temperature alloy steel bolts (e.g., 35CrMoA) with anti-seize compound to mitigate cold welding.
Threaded Connections
Ensure threads are undamaged and sealed with PTFE tape or cryogenic-rated sealant to compensate for thermal contraction.
Avoid over-tightening to prevent 阀体 (valve body) or component damage.
4. Cryogenic Environment Considerations
Pre-Cooling and Condensation Control
Prior to media introduction, gradually pre-cool the valve with low-temperature gas/liquid to minimize thermal shock and prevent seal damage from rapid contraction.
Inspect insulation integrity to prevent surface condensation or icing, which can impair operation and sealing.
Static and Fire Protection
For flammable media (e.g., LNG), ensure anti-static components (e.g., conductive springs between stem and body) are installed to dissipate electrostatic charges.
Verify fire-safe design compliance (e.g., API 607) with metal-to-metal seating to maintain integrity during fires.
5. Operation and Commissioning
Actuation Testing
Manually cycle the valve 2–3 times to check stem mobility and ensure no binding or abnormal resistance.
For powered actuators (electric/pneumatic), perform full-stroke tests to validate position limits and signal feedback accuracy.
Leak Testing
Conduct hydrostatic/pneumatic testing (shell and seat tests) using nitrogen or dry air at specified pressures.
Inspect high-risk areas (flanges, packing glands, welds) for bubble leaks using soap solution or ultrasonic detection.
6. Additional Best Practices
Avoid Forced Alignment: Never use the valve to rectify pipeline misalignment, as this can induce stress leading to deformation or leakage.
Labeling and Documentation: Mark flow direction, operating status, and safety warnings on or near the valve. Maintain an installation log with dates, test data, and component serial numbers for traceability.
