Russia low temperature valve in the industry application

The shipyard is very simple. As a result, there is little room on board. The operator must reduce the volume to make the natural gas tank as small as possible. They do this through liquefied natural gas (LNG, LNG). By cooling to approximately convert natural gas into liquid. -165°C. At this temperature, the main isolation valve must still work.

What influences valve design?

Temperature has an important impact on the design of the valve, and the environment will affect the tightness and durability of the valve. Components of these valves include body, cover, stem, stem seal, ball valve and seat. Due to differences in material composition, these parts expand and contract at different temperatures.

Cryogenic application options

Option 1:

Operators use valves in cold environments, such as oil RIGS in polar seas.

Option 2:

Operators use valves to manage fluids with temperatures well below freezing.

In the case of highly flammable gases, such as natural gas or oxygen, the valve must also operate correctly in the event of a fire.

Pressure problem

There is a build-up of pressure during normal handling of refrigerant. This is due to the increase in heat from the environment and the subsequent formation of steam. Special attention is required when designing valve/piping systems. This allows pressure to build up.

Temperature problem

Drastic temperature changes can affect the safety of workers and factories. Due to the different material composition and the length of time they are subjected to the refrigerant, each component of the cryogenic valve expands and contracts at a different rate.

Another big problem when handling refrigerant is the increase in heat from the surrounding environment. These heat increases are the reason manufacturers isolate valves and pipes.

In addition to the high temperature range, valves also have to deal with considerable challenges. For liquefied helium, the temperature of the liquefied gas drops to -270°C.

Functional problem

Conversely, if the temperature drops to absolute zero, valve function becomes very challenging. Cryogenic valves connect pipes and liquid gases to the environment. It does so at ambient temperature. The result can be a temperature difference of up to 300°C between the pipe and the environment.

Efficiency problem

The temperature difference creates a flow of heat from the warm zone to the cold zone. It can impair the normal function of the valve. It can also reduce the efficiency of the system in extreme cases. This is of particular concern if ice forms on the warm end.

But in low-temperature applications, this passive heating process is also used deliberately. This process is used to seal the stem. Usually, the stem is sealed with plastic. These materials can't withstand low temperatures, but the high-performance metal seals of two components, which move a lot in the opposite direction, are just very expensive and almost impossible.

Sealing problem

There is a very simple solution to this problem. Bring the plastic used to seal the stem to a relatively normal temperature area. This means that the stem sealant must be kept at a distance from the fluid.

The hood is like a tube. If the fluid rises through this pipe, it will warm from the outside temperature. When the fluid reaches the stem sealant, it is primarily at ambient temperature and is gaseous. The hood also prevents the handle from freezing and failing to start.

Select valves for low temperature service

Selecting valves for low-temperature applications can be complex. The buyer must consider the conditions on board and in the factory. Moreover, the specific properties of cryogenic fluids require specific valve performance. The right choice ensures plant reliability, equipment protection and operational safety. The global LNG market uses two main valve designs. Valves are designed to meet the global LNG market

Three bias rotary tight isolation valve

These offsets allow the valve to open and close. They operate with little friction and friction. It also uses stem torque to make the valve more sealable.

Single-flapper and double-flapper check valves

These valves are critical components in liquefaction equipment as they prevent damage caused by flow reversals. Material and size are important considerations because cryogenic valves are expensive. The results of an incorrect valve can be harmful.