three-way valve

Remove the sides first, and finally the ones that are not visible. After removing the three fastening bolts, they may be able to be taken off with a gentle tap using a hammer.

Three-way valve for the safety valve of cryogenic liquid storage tanks, when no other valves are available to shut it off； Look at the direction of the arrow on the valve: when the valve is closed all the way, the left passage is open while the right one is closed; at this point, the safety valve on the right side can be removed ； When the valve is opened to the fullest extent, the right-side path is closed while the left side remains open; at this point, the right-side safety valve can be removed. Only one can be removed at a time; after the safety valve has been tested and found to be in good condition and reinstalled, then the other one can be removed. These valves are part of the low-temperature tank assembly; the gaskets (O-rings) removed from them need to be kept properly, as it is difficult to replace them if they are lost. The original manufacturer must be approached to obtain suitable replacements.

Thank you; the explanation was very professional\ud83d\udc4d\ud83d\udc4d\ud83d\udc4d. The three-way valve is connected to the gas vent pipeline, and there is no shut-off valve at its upstream end. The arrows on the valve are not clear, so I can only disassemble it according to the method you suggested

However, when the three-way valve is opened, frost can occasionally be observed on the lower left branch pipe, while no frost appears on the right side; from this it can be inferred that the left side is the open path