The EJA110e differential pressure transmitter is unstable
Thread Content
A DN300 conical flow meter, equipped with EJA110EJF series differential pressure transmitters, with a measurement range of 0–1 KPa and an operating pressure of 0.05 Mpa. The pipeline pressure is 0.05 MPa, with a typical flow rate of 1600. When the pipeline pressure drops to 0.03 MPa, the flow rate shows as 0. Even when the pipeline pressure rises back to 0.05 MPa, the flow rate remains 0. Considering the possibility of an issue with the differential pressure transmitter, replacing it with a new one did not resolve the problem. Considering that the measuring medium is gas, the pressure tap pipe was cleaned, and the situation remained unchanged. What is the reason for this?
Is it zero as shown on the host computer’s display, or is it zero as shown by the transmitter on site? Additionally, transmitters usually have a drain valve; open it and check whether there is any change in the reading displayed on the pressure gauge； Also, when using a differential pressure transmitter to measure flow rate, a square root calculation is required; furthermore, for gas flow rates, it is necessary to take temperature and pressure compensation into account.
It seems to be coking gas, with low pressure. If my guess is correct and it indeed is coking gas, it’s possible that tar is present in the gas, which has blocked the pressure gauge tube. Therefore, it’s necessary to heat the pressure gauge tube using steam, and then open the drain fitting on the tube to check whether gas is being discharged. Additionally, considering the presence of water in the gas, a drain fitting should be installed at the lowest point of the main pipe for regular drainage. In winter, it’s important to provide steam heating at the front end of the flow meter
Both the primary gauge and the secondary gauge showed zero; everything worked normally after they were reset, but this issue arose once the pressure dropped. The temperature transmitters and pressure gauges are all working properly. The differential pressure transmitter is functioning, but the secondary meter is not; the differential pressure transmitter is not working, yet the secondary meter is working. I’ve tried various approaches.
The pressure tap has been cleaned. Water is also drained regularly. Installed indoors, so there is no need to worry about freezing.
Then we need to consider the selection of flow meters, as all flow meters have a range ratio.
It was all normal before; this phenomenon only appeared recently due to unstable pipeline pressure
Keep the pressure tap as short as possible; direct installation can be considered
With the pressure dropping, does the actual flow rate decrease as well? Consider that the actual flow rate is too low and is outside the measurement range
Was low-level traffic removed (low-signal rejection)?