The pneumatic cryogenic emergency shut-off valve does not return to its original position
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The newly installed LNG cryogenic storage tanks recently have pneumatic cryogenic emergency shut-off valves of model KDJ661F with code T206DA50A. These valves experience the problem of failing to return to their closed position after being opened by air pressure; moreover, the pressure of the medium inside the valves is not high. Such emergency shut-off valves are of the air-operated type. There is a hero who has experience in handling such emergencies; I hope he can offer some help.
One more thing: it’s a pneumatic low-temperature emergency shut-off valve with a single-acting piston actuator that resets using a spring. The model is KDJ661F, and the code is T206DA50A. Yesterday, as the temperature dropped and frost formed, there was again an issue where the valve remained open after the air supply was cut off; however, by noon, when the temperature rose, the valve returned to its original position on its own. No faults were found upon inspection, but it seems that the spring force isn’t sufficient.
It’s likely that the spring material cannot withstand low temperatures, gets frozen and loses its elasticity, which prevents it from returning to its original shape. It was originally a spring, but it froze and hardened until it became like a thin iron rod
Hello, Valve Mingming! The spring is installed inside the pneumatic actuator. Low-temperature valves have long stems, and the temperature of the actuator should not reach a level that would affect the elasticity of the spring. I suspect that the design of the spring’s pushing force is too idealized – if the force is a little too strong, it won’t be able to function properly. But this emergency shut-off valve needs to remain closed at critical moments, which is really concerning
It is recommended to check whether there is any freezing blockage in the gas supply pipes or the exhaust outlets! Seemingly breathless, but in reality not completely emptied. For reference!
Thank you! The inlet connector of the actuator’s air supply pipeline was removed, but it still did not return to its original position; the instrument air had been treated with adsorption drying, and there were no issues of blockage at the exhaust port.
6# hcwang12345 is not very familiar with the specific structure of pneumatic actuators; if a picture could be sent, it would make the analysis more accurate. It’s recommended to check the exhaust valve again! For reference!
This post was last edited by QHDKD on 2009-11-26 at 01:15. It would be best to check the areas where dry ice has frozen on the outside, and also to examine the piston shaft of the actuator – condensed water might have flowed into the piston and frozen there. Check for any signs of dry ice formation; use manual heating methods for inspection. There may also be leaks in the lower seal of the valve, which could lead to the accumulation of condensed water, with this water rising to colder areas. I have been selling low-temperature valves for many years; if you are interested, we can discuss this further.
Personally, I think the view on the 8th floor is the most likely one. If it happens again, try blowing air into the cylinder with steam to see if it returns to its original position. Also, what is the medium inside the valve when it is in normal condition? Is there a orifice plate behind this valve?
The 7# clguan pneumatic actuator is of the piston type with a straight stroke; the valve body is of the globe valve type. The valve operates in an air-actuated mode and is reset by a spring.
The valve contains liquefied natural gas at a temperature of -165°C, and there is no orifice plate downstream of the valve.