Does an ultrasonic syngas flow meter require temperature and pressure compensation?
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What we do now is: the value selected in the field table is in cubic meters, and temperature and pressure compensation is applied after it reaches the control system. I’m not sure if this approach is correct.
Generally speaking, measurement principles that rely on flow velocity all require temperature and pressure compensation. When setting up your flow meters, are there options for selecting the gas type, pressure, temperature, etc.? If all these are specified and cubic meters are chosen as the unit of measurement, then no temperature and pressure compensation is required on the DCS side
This post was last edited by ZhiGE on 2020-2-27 at 15:58. 1. The gas velocity inside the pipe, as measured by an ultrasonic flow meter, is multiplied by the pipe area to obtain the volumetric flow rate. 2. If temperature and pressure are not fed into the ultrasonic flow meter for compensation, the output should be volumetric flow rate rather than standard cubic volume. 3. Connect the 4–20mA signal corresponding to the above values, without any compensation, to the DCS; temperature and pressure compensation is then performed within the system, and the resulting value represents the standard volumetric flow rate. 4. If there is no compensation at the site, and the transmitter is set to standard cubic units (if the built-in pressure and temperature compensation of the transmitter is not used), the value will be uncompensated, but the unit will be standard cubic units. It is the same as the DCS unit, but the value is different. It is prone to causing misunderstandings. So it is better to set it as volumetric flow rate rather than standard volumetric flow rate.
“The value selected on the field gauge is in standard cubic feet; temperature and pressure compensation is applied once it reaches the control system. The value output by the field gauge in standard cubic feet is already in that unit, so no further temperature and pressure compensation can be performed – otherwise it would result in repeated calculations of such compensation, which is incorrect.
We are the fourth type: fixed compensation set within the boundaries, with the selected unit being cubic meters. Then the system compensated back to the operating pressure and temperature! Isn’t this approach simply the operating flow rate!