LNG Cryogenic butterfly valve with maintenance port

With the high attention paid by humans to environmental pollution in recent years, countries and even the world are striving to develop clean energy to gradually replace traditional energy sources with greater pollution Especially liquefied natural gas, as a clean energy source, is increasingly favored,even more explosive growth has been achieved. With its development, cryogenic valves, as the key control and cut-off parts, have put forward new requirements for it.
For this reason, we,JUDU noticed this as early as around 2008 and has developed LNG cryogenic butterfly valves (nominal diameter 8 "-42", pressure level 150LB-300LB) for multiple domestic and foreign companies.

Flange connection structure cryogenic butterfly valve

The commonly used flange connected cryogenic butterfly valve structure in China is modified based on the original conventional triple eccentric butterfly valve. There are two main derived structures. The first is to keep the internal structure unchanged and extend the bracket. The disadvantage of this structure is that the valve seat sealing structure cannot adapt well to micro deformations under cryogenic conditions, making it difficult to achieve effective sealing; The second method, as shown in the figure on the right, involves changing the valve seat to a movable structure and using positioning plates, valve seat pressure sleeves, etc. to press the movable valve seat into the inner cavity of the valve body. The secondary structure optimizes the valve seat structure, making it movable and compensating for the leakage problem caused by deformation under temperature cross changes; Disadvantage: It does not implement online maintenance. When the valve internals need to be replaced normally, the valve must be disassembled and replaced first.

Side mounted structure cryogenic butterfly valve with maintenance port

A side mounted structure with maintenance port ,that not only ensures reliable sealing even in an extreme environment of -196℃,but also can convenience of repairing and replacing internal components online. On the basis of the previous structure, a manhole is opened on the side, and the butterfly plate and sealing components are installed through the maintenance port. When the valve needs maintenance, open the maintenance cover to enter the inner cavity and replace the internal components.

Main features of side mounted structure cryogenic butterfly valve with maintenance port

Triple offset structure design

1st offset: Axial eccentricity, the sealing surface is placed on one side of the valve stem, and the sealing surface is eccentric to the valve stem.
2nd offset: Radial eccentricity, the centerline of the valve stem deviates from the centerline of the pipeline, and the valve stem is eccentric to the center of the channel.
3rd offset: The apex of the cone is eccentric, and the circumference of the elliptical sealing ring is extended to form a regular cone, with the apex of the regular cone eccentric to the center of the channel.

Packing

The packing adopts EagleBurgmann fugitive emission composite packing, and its end ring is woven with carbon fiber and expanded graphite. The inner edge of the end ring has a high-density graphite ring, and the middle is a cup-shaped high-density expanded graphite ring, which meets TA luft, ISO15848, API622, AP1589 and other standards.

Long Neck Valve Cover and drip board    

Adopting a long neck valve cover structure design, the position of the packing box is raised to enable the packing to work in an environment above 0 ℃. By combining theoretical calculations, finite element analysis, and experiments, the optimal valve cover extension length and wall thickness are determined to minimize heat loss as much as possible.
The drip board structure design effectively slows down the transmission of valve body temperature to the packing and upper end of the valve body, ensuring that the temperature of the packing and upper parts of the valve stem is above 0 ℃. The drip board effectively prevents low-temperature wavy water vapor from dripping onto the flange bolts and causing corrosion.

Floating sealing ring

A floating sealing ring is used, which can adjust its position on the valve body according to the thrust when the valve plate is closed. This floating seal can compensate for factors such as deformation and thermal expansion of the valve body under low temperature conditions, eliminate damage to the sealing surface, ensure uniform sealing pressure, extend the service life of the seal, and improve the sealing effect of the metal hard seal. This structure fundamentally solves the problem of sealing leakage caused by temperature changes.

Maintenance Port

The use of a valve body with maintenance port enables butt welded valves to be repaired without the need to remove the entire valve, butterfly plate, valve stem, and other related connectors from the fluid pipeline. The detachable sealing pair design makes maintenance and replacement of the sealing pair more convenient and efficient. The valve cover with lifting rings for inspection makes maintenance more convenient.

This structure of the new online maintenance butterfly valve can not only replace a large number of existing butterfly valves on LNG pipelines, but also be widely promoted and used in other places where it is inconvenient to disassemble valves on similar main pipelines. In fact, in various process pipelines such as petrochemicals in China, there are many places where work cannot be stopped 24 hours a day, or can only be temporarily stopped during emergency repairs. At this time, if the valve is dismantled and partial repairs are carried out, the time is long, the efficiency is low, and the cost is high, especially in the difficult positions of dismantling and hoisting large-diameter pipelines. This structure effectively avoids these problems, greatly saving time and reducing costs.