1. LNG Cryogenic Ball Valve - This is the most widely used and most common valve in the LNG system.
Structural Features
Long Neck Bonnet: Comes Standard.
Anti-blowout stem: Helps prevent the stem from being blown out when pressure is inside.
Dual shut-off and venting function: When the valve is turned off, a venting valve helps release the LNG that is locked in the valve chamber. This action prevents any abnormal pressure rise caused by vaporization.
Special Ball Seat Design: Usually involves a metal to metal seal or soft seal with compensation for cryogenic shrinkage.
Applications:
Natural Gas Liquid storage tank Inlet/Outlet
Connections to the loading arm
BOG (Bottle-Off Gas) handling
Starting and stopping pressure regulator skids as well as vaporizers
Closing general process pipelines
2. LNG Cryogenic Shut-off Valve - For use where a high degree of flow control or shut-off is desired.
Riemann Surface
Angle or Y type valve body: Low flow resistance, easy discharge, no media retention.
Disc-shaped bonnet: Able to support stress due to changes in temperature.
Bellows Seal: One of the key components. The bellows, which is strongly welded to the valve stem, creates a metallic sealing barrier to ensure the complete impossibility of leakage of the valve stem packing at low temperatures, giving the highest guarantee for the 'zero external leakage' function.
Uses: Pipelines that need accurate fluid control (analytical sampling systems, for example)
Toxic applications with high sealing demands
BOG COMPRESSOR INLET/OUTLET
Instrument air and Nitrogen Pipelines
3. Cryogenic Gate Valve-LNG - In large-scale LNG transmission lines where a full-bore, low resistance, and full closure functionality is demanded.
Structural features: Rigid wedge or resilient gate: This is used for adjusting the differences in the rate of contraction between the valve body and the gate at low temperatures.
Full bore design: Least resistance to flow, thus smooth passage of the pigs.
Also features long neck bonnet, anti-blowout valve stem.
Applications: Trunk pipelines handling LNG requiring full-bore operation.
Bulk inlet and/or outlet piping in an LNG reception plant or liquefaction plant.
4. LNG Cryogenic Safety Valve/Relief Valve - An extremely important safety relief device protecting equipment and pipelines from overpressure damage.
Structural Features: Primarily developed for gas-liquid two-phase flow mediums.
The spring chamber is isolated from the cryogenic fluid and hence the performance of the springs is not affected by the low temperature.
The sealing surface and the actuating mechanism have to be highly reliable; they must open just at the set pressure and close firmly when re-seating.
Applications:
LNG storage tank components (main & spare safety valves)
Overpressure Protection of LNG Pipelines and Storage Tanks
Bog systems
5. LNG Cryogenic Check Valve - This will prevent backflow of the fluid and will safeguard several critical components on the LNG
Structural Features: Mainly found in swing and lift configurations.
Its valve disc is lightweight, thus quick-acting when handling small flows.
High-quality seal, with no leakage from back pressure. Applications: Prohibiting backflow of media during pump shutdown, LNG pump outlet. Compressor Inlet & Outlet. Pipelines where backflow is possible. 6. Other Special Valves Cryogenic Butterfly Valves: For the regulation or isolation of the large diameter, low differential pressure circuits used for ventilation and BOG lines. Needle Valves: These control small flow rates and are commonly found in instrument pressure lines and sampling lines.