06. June 2016 · Comments Off · Categories: Uncategorized

Why cryogenic ball valves prone to pull stuck motionless phenomenon, how should it be solved?

A: The low temperature ball valve(cryogenic ball valve) installed at room temperature, work at low temperatures large temperature range. If the design, improper installation, it is prone to heat stress or strain. At the same time, the ball valve is in the normal operating portion, circulation portion is low. To reduce cold damage, stem often do very long, it is easy to be deformed and stuck. Cryogenic ball valves(low temperature ball valves) are often rotated at room temperature flexibility at low temperatures is very tight, and even open. Valve stuck at low temperatures the main reasons are:
1)The installation, low temperature ball valve(cryogenic ball valve) and pipeline configuration unreasonable generate prestressing; or poor pipe cold compensation, at a low temperature ball valve(cryogenic ball valve) position change; or lack valve stent deformation at low temperature; or ball fixed properly, cold box at a low temperature deformation The influence of concentricity with the valve stem.
2)In the design, because of the different stem and the low temperature ball valve(cryogenic ball valve) sleeve material, the linear expansion coefficient is different. Usually the stem stainless steel, linear expansion coefficient of 1.73 × 10-6 ℃ -1; brass sleeve, linear expansion coefficient of 19.9 × 10-6 ℃ -1, i.e., greater than the contraction brass stainless steel, low temperatures may the threaded bite. Especially when using fine thread, threaded a temperature range of large and small thread gap, the phenomenon is more prone to bite.
3)In the operation, due to the low temperature heating is not complete at the ball, or valve packing at the water, causing freeze, or at room temperature, the valve is closed tight at low temperatures, making threaded chewed like.
To prevent hypothermia valve stuck phenomenon, the design should be broad trapezoidal screw threads; there should be a firm stand in the valve at the installation to prevent the valve with the stem pipe displacement and bending. Ball and low temperature cold box can be elastically fixed connection to prevent deformation of the stem and the body different heart; during the cold bare, to check and adjust the cryogenic valve installation in the cold state, when it was found jammed valve cooling When the phenomenon, adjustable valve mounting flange on the cylinder housing, so that the switch easily.
In operation, before the start of the heating should be complete, close the low temperature ball valve (cryogenic ball valve) when the principle of not leak, do not use excessive force.

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