Help! Equipment failure
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The company has a differential pressure transmitter of the EJA brand, which is used to monitor the level in a condenser. It has been malfunctioning since it was put back into operation after the last maintenance session. The trend diagram is shown below. Since the company does not allow the use of mobile phones, I drew the diagram myself. The problem is that the level gauge rises rapidly every once in a while, either every minute or every two minutes, until it reaches the full scale; after a few seconds, it drops back down to normal levels, and this cycle repeats over and over again. Initially, the field gauge was replaced, but the transmitter continued to exhibit the same issue after the replacement. The company uses HILI control systems. When troubleshooting issues with the cards in the control room, the replacement method was applied: another, less important transmitter was connected to the terminals of the card that was experiencing problems. No issues were detected, so it was concluded that the problem lay with the card itself. However, the fault persisted. The instrument functioned normally for a while, only a few days, before the problem reappeared. I’m seeking help from all experts here – what could be the cause of this, and where should we start investigating?
If the operating conditions permit, it is possible to consider increasing or decreasing the liquid level by 10–20% to see what happens; this will help determine whether the liquid level control point is exactly at the gas-liquid interface
Have you checked the wiring from the field panel to the Allen-Bradley safety barrier?
We have a similar situation as well; the level gauge on my ball tank reaches its full scale once or twice per shift. After checking for a long time, the instrument showed no problems. Could you please help diagnose this issue?
Please check whether the cable shield is grounded at one end and whether the cable is twisted pair.
Are you saying that you suspect interference is being introduced due to poor connections?
1. Check whether the pressure source experiences periodic fluctuations. 2. Check for interference around the shield wire and whether isolation barriers have been installed. 3. The low-pressure side of the transmitter (L) generally contains no liquid; if there is liquid present, it should be drained
On our side, at the low-pressure end, there’s a condensation tank; negative migration has occurred there