How to troubleshoot DP type flow transmitters

In this article, you will find how you can Troubleshoot the DP type flow transmitters with each problem and its solutions.

Introduction

Welcome again to this series of articles on maintenance jobs related to instruments. Today in this article, we will learn the maintenance jobs for a DP-type flow transmitter.

DP-type flow transmitters are used widely along with different primary sensing elements like orifice plates, venturi tubes, pitot tubes, averaging pitot tubes, and many more. So, let us learn the maintenance job procedure for the DP-type flow transmitter.

Problem> DP-type flow transmitter showing Zero

Solutions:

1. Check the isolation valves in process fluid tubes. All isolation valves to the manifold should be open.
2. Also, in the manifold, isolation valves should be open and the equalization valve should be closed.
3. Check whether the vent port is properly fixed or not.
4. The tube might be choked fully. Follow the procedure to dechoke the tube.
5. Ensure that the HP side of the primary sensing element is connected to the HP side of the transmitter and that the LP side of the primary sensing element is connected to the LP side of the transmitter.
6. Any force from DCS/PLC/ESD can be present. Even the transmitter can be in simulation mode. Remove it.
7. The DP-type flow transmitter can be in power-off condition. Check the voltage. If it is not present then check the whole loop for problem. This loop includes cable terminations, fuse, barrier, and cable condition.
8. The primary sensing element in the line might not be installed properly. Check it.
9. DP-type flow transmitter might have become faulty. Replace it and do the necessary configurations as per the datasheet.
10. The Analog input channel might be in a faulty condition. This is a rare case. Change the channel and do the necessary configurations.

Problem> DP-type flow transmitter showing low value

Solutions:

1. Check the isolation valves in process fluid tubes. All isolation valves to the manifold should be open. None of them should be in throttled condition.
2. Also, in the manifold, isolation valves should be open and the equalization valve should be closed. None of them should be in throttled condition.
3. The tube might be choked fully. Follow the procedure to dechoke the tube.
4. Attend leakage in the tube if any leakage is present.
5. Ensure that the HP side of the primary sensing element is connected to the HP side of the transmitter and that the LP side of the primary sensing element is connected to the LP side of the transmitter.
6. Check the transmitter by giving pressure as per range and do calibration if needed.
7. Check the square root functionality. If it is configured as linear then the flow reading will be low. Make it to square root.
8. The primary sensing element might be having an issue. First, flush if properly, if it does not work, then do back flushing with more pressure if permissible as per process. The last option is to remove the primary sensing element do an inspection and take necessary action.

Problem> DP-type flow transmitter showing high-value

Solutions:

1. Any of the isolation valves can be in closed condition. Open the isolation valve (usually low side).
2. Check the transmitter by giving pressure as per range and do calibration if needed.
3. The primary sensing element might be having issues. First, flush it properly, if it does not work, then do back flushing with pressure if permissible as per process. The last option is to remove the primary sensing element do an inspection and take necessary action.

Problem> DP type flow transmitter value not stable

Solutions:

1. Check the isolation valves in process fluid tubes. All isolation valves to the manifold should be open. None of them should be in throttled condition.
2. Check the condition of the isolation valves in the manifold. Isolation valves should be open and equalization should be closed.
3. The tube might be choked or partially choked. Dechoke it and flush it properly.
4. Attend tube leakage if leakage is found.
5. The primary sensing element might be having the issue. First, flush if properly, if it does not work, then do back flushing with pressure if permissible as per process. The last option is to remove the primary sensing element do the inspection and take necessary action.

Problem> DP-type flow transmitter showing the constant value

Solutions:

1. Check the isolation valves in process fluid tubes. All isolation valves to the manifold should be open. None of them should be in throttled condition.
2. Check the condition of the isolation valves in the manifold. Isolation valves should be open and equalization should be closed.
3. The tube might be choked or partially choked. Dechoke it and flush it properly.
4. Check the transmitter by giving pressure as per range and do calibration if needed.
5. Any force from DCS/PLC/ESD can be present. Even the transmitter can be in simulation mode. Remove it.

Problem> DP type flow transmitter incorrect in the field and on DCS/PLC/SCADA

Solution:

1. Check the range of field display in the transmitter and on the DCS/PLC/SCADA. It will be either different or in mmH2O. Configure proper range as per documents.

Problem> DP type flow transmitter displays off

Solutions:

1. Display failure is one reason. Replace the display and do the necessary configurations.
2. The DP-type flow transmitter can be in power-off condition. Check the voltage. If it is not present then check the whole loop for problem. This loop includes cable terminations, fuse, barrier, and cable condition.
3. DP-type flow transmitter might be faulty. Replace it and do the necessary configurations.

EndNote

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