Liquefied gas: loading, excess amount
Thread Content
Have you encountered the problem of excessive loading of liquefied gas during actual production? For example, in summer the filling coefficient is relatively lower, which results in the actual amount loaded being higher than the safety requirements. If so, how is it handled? Experts in storage and transportation, as well as those working on the front lines of operations, are welcome to join the discussion.
Putting it back on the vapor line is more practical.
It’s okay to put back a small amount at the vapor phase line, but not a large amount. Moreover, when the gas phase pressure is high, it becomes difficult to return it to the tank. If there is a unloading line, unload it back into the tank. If not, it can only be placed on the vapor phase line. If it is at a liquefied gas station, it can be returned to the tank using a compressor. It’s always a problem, so strict control is necessary to prevent overloading.
1. If a compressor is available, use it to pump the excess amount back into the tank. 2. High-pressure nitrogen is injected through the gas line of the tank truck to force the excess amount back into the tank
Discharge the flare – using nitrogen is definitely not feasible, as it will cause overpressure in the tank truck
Reply to 2# liugui1998: Loading is complete; the pressure in the tank truck should now be the same as that in the spherical tank. No more gas from the tank truck will circulate into the spherical tank. In the structure of a tank truck, the upper part of the vapor phase line is close to the upper wall of the tank, whereas the liquid level allowed during filling generally does not reach this position. How can the liquid phase return to the vapor phase line? (Should the loading design include a cross-line between the liquid phase and the gas phase?) ）
Reply to 3# cityhummer: Is it necessary to take into account unloading requirements when designing the loading process? Can it be used for both loading and unloading?
Reply to 4# lhyln: What is the nitrogen pressure in your facility’s utility system? Can it get into the liquefied gas pipeline? Even if possible, the liquid phase returning along its original path would pass through the check valve at the pump outlet (unless an additional line is added in front of and behind the loading pump to bypass the check valve).
Reply to 5# cy0404020: Perhaps this is a more practical approach.
Reply to 6# Mysterious Beyond Mystery: Transfer the refineries and gas stations in the north to the south, especially in winter. All have reached an overloading level of 95% ； The heaviest I’ve seen was a 25-ton vehicle loaded to 30 tons, almost full. One can try to connect the gas phase and the liquid phase using a hose and quick connectors; by modifying the connectors, this can be achieved. After loading and unloading, once the gas phase and liquid phase are connected, air can be blown back in ； But a bypass needs to be added at the pump location (a check valve, as the pump can’t pass through it).
Now, loading systems are required to be equipped with quantitative loading systems to prevent overloading, but older enterprises did not have such designs at all. Driven by profits, some people will take risks out of a sense of luck, ignoring the dangers of overloading. In fact, only minor modifications to the pipeline are needed, so that the pressure difference can be used to push the excess volume back into the tank. Out of a sense of responsibility and in compliance with regulatory requirements, design institutes generally provide a designed quantity for loading, rather than making simple modifications.