Mass flow meters provide inaccurate measurements for gas-liquid two-phase media
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The medium is propane, and a fixed-volume filling system is used for tank trucks; measurement is carried out with a mass flow meter. Due to the property of propane existing in both gas and liquid states, the mass flow meter provides inaccurate readings. Safety regulations prohibit overfilling – is there any effective way to remove the gas? ? ? Or how to ensure accurate measurement? ? ? (The site does not have the conditions to be linked to a scale.)
This problem is indeed quite troublesome. Propane is a medium that vaporizes easily, and mass flow meters indeed give inaccurate readings in a gas-liquid mixture state. Here are some practical suggestions for you: 1. The simplest solution is to install a gas eliminator, which is a small separation device placed in front of the flow meter to remove the gas first, allowing only the liquid to enter the flow meter. Many chemical plants handle liquefied gas in this way. 2. It is possible to consider cooling the tank trucks appropriately before filling, for example by using spray water to reduce the vaporization of propane. However, it’s important to ensure that the temperature isn’t too low. 3. If conditions permit, a sufficiently long straight pipe section can be added before the flow meter, allowing the fluid to stabilize first and reducing gas-liquid mixing. 4. Another option is to use a mass flow meter with dual measurement capabilities; this device can measure both density and flow rate simultaneously. By monitoring changes in density, it’s possible to determine the degree of vaporization and automatically compensate for any errors. If there’s no weighbridge available on site, it’s recommended to install a degasser as a priority—this modification is relatively simple and yields noticeable results. Remember to check the exhaust valve regularly to prevent the exhaust outlet from getting clogged. .
The best way to address this issue is by addressing the causes of the formation of the gas-liquid two-phase mixture. Loading racks designed in accordance with general standards do not cause severe gas-liquid two-phase conditions. The main focus is on checking the pipelines and loading platforms to identify the cause; it is necessary to determine whether the pipeline layout is appropriate and whether the flow meter is installed in the right location. The pressure and temperature of the medium also need to be taken into account. Generally, the gas-liquid two-phase phenomenon can be reduced by increasing pressure, lowering temperature, or using buffer tanks. After loading, it is weighed, with the scale providing the final measurement data. I didn’t understand your last part (there are no conditions at the site to link it with the scale).
In the case of spherical tank equipment, with proper temperature control of the pipelines, a two-phase gas-liquid condition will not occur during loading.
No flow meter will work well in a gas-liquid two-phase system; apply back pressure, lower the temperature, and add degassing
Add a gas phase tube above it, and also install a mass flow meter there