LPG loading operation
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Everyone, when loading LPG at your plant, is the vapor equilibrium line connected to the tank truck or is it closed?
Theoretically, it should be connected.....
If the nitrogen content inside the tank truck can be ensured, then the gas phase can be connected in order to speed up the loading process and increase the filling efficiency. If it is not certain or there are concerns about nitrogen entering the storage tank, then no connection is made; however, this will result in incomplete loading or insufficient pressure at the pump outlet.
From the perspective of the balance line, it is necessary to ensure connectivity; the main purpose is to guarantee a smooth unloading process with thorough drainage, otherwise a very high pump pressure would be required.
It is determined based on actual conditions; if there are no quality requirements, the gas phase can be connected to ensure the loading volume； If there are requirements for gas-phase quality, it is recommended not to connect them.
Our factory is interconnected, which improves the efficiency of loading and unloading vehicles; meanwhile, if the pressure in the tank trucks becomes too high, the drivers refuse to work
Recently, I conducted investigations at two large Sinopec facilities in Jiangsu and Zhejiang. When using mass flow meters for measuring liquefied gas during loading (rather than unloading), the gas-phase equilibrium lines are always set to a closed state. There are two reasons for this: 1) Some tank trucks deliberately fill them with nitrogen before loading, in order to cheat and replace higher-value products; nitrogen entering the liquefied gas storage and transportation system increases the operating pressure of the entire system, creating potential hazards； 2. During loading operations, the gas-phase flow meter often shows a significant deviation compared to the liquid phase, which can lead to measurement issues. Regarding the above two questions, I would like to seek advice from the experts here.
Check the pressure inside the tank truck; it should be turned on when the pressure is higher than or equal to the pump outlet pressure. Also, check the flow meter reading – if the reading increases too slowly, then vapor should be introduced; it cannot be turned on in advance. Poorly trained drivers may use nitrogen or other non-condensable gases to displace the liquefied gas!
Dear sea friends: The procedures for balancing the gas phase in liquid hydrocarbon storage tanks are as follows: (1) Tanks containing the same medium are connected together at the upper part of the spherical tank, that is, in the gas phase section, via pipelines to form a gas phase balance line. It should be kept closed at all times. (2) When the pressure in the static tank or receiving tank is too high, pressure can be relieved to a lower-pressure tank by means of the vapor line. Too low pressure in the feed tank may cause the pump to experience vacuum; in such cases, a tank with higher pressure can be used to increase the pressure in the feed tank via the gas line. (3) When a new tank is put into use, a qualified medium of the same type is used for gas-phase equilibrium. Close the gas phase valve after pressure balance is achieved. Pre-pressurize the storage tank to prevent pressure and temperature shocks caused by rapid vaporization of the feed gas. If loading occurs, the pressure inside the tank will surely increase toward the end of the loading process; at this point, it is necessary to open the vapor equilibrium line to release pressure into the tank containing the same medium, thereby ensuring smooth loading.