LPG loading, treatment of residual liquid in flexible connections
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After the liquefied gas is loaded onto the vehicle, the liquid phase of the liquefied gas is sealed off in the pipeline at the pump outlet. Generally, there is a ball valve at the end of the pipeline connected to the flexible hose; what happens to that portion of the liquefied gas liquid phase that is sealed off by the ball valve? After all, when the ball valve is closed, the temperature of the liquefied gas in the flexible hose rises, which can likely cause the hose to burst (I’ve heard of similar safety incidents). Here, we don’t close the ball valve tightly, and instead rely on the internal leakage of the check valve at the pump outlet to absorb the pressure generated by the expansion of the flexible hose, but this isn’t considered a proper solution. Everyone is welcome to join the discussion.
Generally, there is a safety valve that can activate when overpressure occurs. Then jump back to the gas phase pipeline.
Without a safety valve, it can’t launch; I’ve encountered this before – several units broke down in the summer, which is very dangerous. Looking forward to introductions from experienced peers.
The loading hose does not have a safety valve; it only has a ball valve on the quick connector, and it is prone to leakage. The several types I have seen are as follows: 1. (LPG station) Connects to the gas phase line in the gas station to clean the liquid ； Place it in a well-ventilated and cool area that is free of vents, where the volume expansion of the liquid phase is 250 times that of the gas phase, which expands much less. It is a decent approach. II. (At the refinery) Install a nitrogen line at the front of the hose; after loading and unloading, a simple purge is sufficient. III. Install a constant-pressure check valve in the pipeline, which will automatically release pressure when it exceeds a certain level. However, the valve connected to the hose cannot be closed, as doing so would create a dead end at the hose. There’s nothing that can be done about internal leakage in the ball valve at the end; it has to be replaced with a new one.
Make a joint at the gas phase line; after loading and unloading are complete, discharge the liquid phase into the gas phase