Regarding the quantitative loading of propylene
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Propylene belongs to liquefied hydrocarbons. When loading it in quantified amounts, it is necessary to install mass flow meters on both the liquid-phase pipe and the gas-phase pipe. Since the initial pressure of tank trucks varies, and propylene tends to vaporize easily, mass flow meters are installed on both pipes; the cumulative flow value from the liquid-phase pipe is then subtracted from that of the gas-phase pipe to obtain an accurate amount loaded. I would like to discuss with everyone whether it is really necessary to install a flow meter on the gas-phase pipe
It needs to be weighed before leaving the factory, right? If that’s the case, there’s no need to add it to the gas phase tube
I don’t think it’s necessary to install a flow meter in the gas pipeline; the flow meter is there merely to monitor the amount loaded and to prevent overloading or underloading. Even for liquefied gas, the quantity is determined by weighing. Calculating in the gas phase is too troublesome.
Due to the special properties of liquefied gas media such as propylene, the accuracy of the quantitative loading system for propylene is not high; therefore, the significance of such a system is limited. It goes without saying then that installing a mass flow meter in the gas phase is unnecessary (as it would lead to waste).
I’m currently working on a loading project, which involves installing a mass flow meter on the vapor line, as mentioned by the original poster. This issue has to be discussed with the user; what’s the point of adding it if there isn’t enough budget for it? As long as the quantitative loading system supports this application, that’s sufficient. The advantage of doing this is that it’s possible to compare the readings from the quantitative loading system with those from the weighbridge; if the system is stable, the difference between the two values should be within a very small range. The users of my project require that this difference be within 0.2%, otherwise it’s considered unacceptable, haha.
A reminder: When loading propylene, care should be taken as there is a possibility of backflow in the vapor line, as the pressure in the propylene storage tanks (spherical tanks) is quite high. Especially in winter, the pressure in the propylene tankers is lower; if the vapor line is opened as per the operational requirements, material backflow will definitely occur. Special attention must be paid when designing the flow meters.
If delivery is to be carried out in accordance with user specifications without the use of a weighbridge, an additional cost will be required; if a weighbridge is available, no additional cost is needed. For commercial-grade delivery, it is recommended to use a weighbridge for loading the propylene, as this method yields better results than using flow meters