Uses of Cryogenic Valves

Cryogenic valves are mostly found in industrial facilities to harness the benefits of undergoing processes at cryogenic temperatures. Thus, the following sections highlight some of these applications.

Liquid Nitrogen Gas (LNG) Terminals and Plants

In the oil and gas industry, cryogenic valves serve in the control of liquified gasses such as liquid nitrogen, methane, and helium. Because of the ease and safety of non-pressurized storage and transport, these elements cool to cryogenic temperatures, so they remain in the liquid state. As a result, larger volumes can be transported or stored for some time, while the piping system operates at much lower pressure levels. Before cooling these gasses into liquid, it is necessary to remove condensate, moisture, CO2, and H2S to prevent corrosion problems downstream.

From World War II, the field of cryogenics enjoyed accelerated development with its eventual commercialization in 1966 by Ed Busch. Busch increased metal tool design life by up to two to four times via cryogenic tempering rather than heat treatment. As a result, it is common to find cryogenic valves and accompanying equipment in steel production plants today. Another area of use is in the freezing of foods and biotech products such as vaccines.Aerospace Applications

In the aerospace industry, cryogenic fuels have gained wide acceptance over the years. Liquid hydrogen and liquid oxygen often serve as propellants for space shuttles, either alone or in combination with jet fuel. The presence of cryogenic valves is a must in such systems.

Types of Cryogenic Valves

As previous sections highlight, there are a variety of cryogenic applications. Similarly, there are a variety of valve types that can serve in these applications, with each having its own benefits. Thus, it is necessary to select the right type that suits an application. Generally, a basic feature of all cryogenic valves is having a tight shut-off. Cryogenic fluids are sensitive, and any leakage can cause harmful and expensive damage.

Cryogenic Butterfly Valves

The triple-offset butterfly valve is an ideal option for cryogenic service. This is due to its non-friction, metal-to-metal seal that provides bubble-tight shut-off and the long-term integrity of the sealing mechanism. Additionally, they offer quick opening and closing action and are the ideal choice for remote operation. The Durco TX3 butterfly valve provides such an example – with excellent shutoff capabilities, low torque, and reduced wear benefit.

Cryogenic Globe Valves

These valves have a spherical shape with a disc that rotates 90° to the plane of its body seat. Therefore, it provides effectiveness for long-term sealing. However, they may not resist erosion for long and are not recommended for systems with high flow rates. Ideally, globes should be provided with a full Stellite valve trim to protect against erosion. Cryogenic fluids tend to lose their lubricity, and the Stellite helps to reduce the wear and tear on the valve.

Cryogenic Ball Valves

The most common valves for liquid gas applications are the double-seal ball valves such as the L&T and AMPO Poyam. Generally, they offer better flow characteristics than globe valves. Also, they are very efficient in providing a tight seal. They also incorporate a vapor space of sufficient height that allows gasification in the area below the gland. Consequently, this keeps the gland packing near the ambient temperature as thermal conductivity between the inside and outside of the valve is limited. Yet, due to wear concerns along the seals and the ball, they find preference in applications with an unrestricted flow path.

Cryogenic Gate Valves

A typical cryogenic gate valve has a wedge-shaped gate, which opens and closes in line with the mating body seat. As a result, there is minimal pressure drop when in a fully open position. Thus, it provides desirable flow characteristics. For larger valve sizes, gate valves such as the Poyam, L&T, and the smaller forged NEWCO Douglas-Chero are preferred in place of ball valves, which can be more costly. However, gates are more difficult and expensive to actuate in comparison to butterfly valves, especially as their size increases, so they are not ideal for remote operation. Gates can be prone to wear and tear if they are subject to often repeated opening and closings. An advantage gate valves have is that due to the metal-to-metal sealing surfaces, they are not subject to the cold flow that Teflon seals in ball valves tend to see.