How to Troubleshoot On-Off/Shutdown Valves

In this article, you will find how you can Troubleshoot the On-Off/Shutdown Valves with each problem and its solutions.

Introduction

Welcome to the 2^nd article of this series.

In this article, we will discuss how you can Troubleshoot the On-Off/Shutdown Valves. On-off valves are equipment that has a high failure rate as compared to other equipment.

If any on-off valve gets stuck or does not operate then it can have an impact on the whole process. So, it is one of the most important items of equipment for our plant. So, let us start with this topic.

Below are all the problems that we face in an on-off valve with their solutions.

> Problem: On-Off valve feedback issue

Solutions:

1. Check the condition of the on-off valve as per command. If the command and the field position are the same, then the feedback issue is there. Set the limit switch or proximity whichever is applicable.
2. If setting the limit switch or proximity does not work, then check the voltage in this loop. The fuse might be blown. Replace the fuse if it is blown.
3. If the voltage is okay, then the limit switch or proximity might be faulty. Replace it.
4. If the fuse and limit switch or proximity are okay, then the barrier in the marshaling cabinet might not be working. Try replacing it.
5. The feedback might be forced. Check it and remove it if found forced.
6. If the above solutions do not work, then in the worst case, the digital input channel might have become faulty. Change the channel and do configurations.

>Problem: On-Off valve not opening or closing fully and getting stuck in between

Solutions:

1. Check the instrument’s air pressure. Set it as per the air pressure mentioned in the datasheet.
2. Check the instrument air tubing leak. If the leak is there then attend to the leak.
3. Check the actuator for passing. If it is passing then attend it by replacing it or overhauling it.
4. If the actuator is okay, then check the condition of the SOV. It might be passing.
5. Check the limit stop bolt in the actuator and gearbox. They might not allow the valve to open or close fully. Adjust it.
6. Check the valve by giving direct air. The body might be stuck. Rouse it a few times. This might solve the issue.
7. Drop the valve if it is still not operating and do an overhauling.

>Problem: On-off not opening or closing

Solutions:

1. Check if any interlock is present which is not allowing to operate the valve.
2. Check whether the SOV is latching type or not. If it is a latching type, then make sure that the latching system is working properly.
3. Check the handwheel on the valve. If it is latched, then it will not allow the valve to operate.
4. Check the voltage on the solenoid valve. Voltage might not be present. If this is true then, check the fuse in the marshaling cabinet. Replace it if found blown.
5. Check the relay in the marshaling cabinet. It might be faulty. Replace it if found faulty.
6. Check the DO channel’s output. It might also become faulty. This is a rare case. Change the channel and do the necessary configurations.
7. Check the SOV’s coil resistance. If found high or low, replace it.
8. Check the condition of the SOV’s body. It might be passing or the plunger might be stuck. Replace it if it is not proper.
9. Check the instrument’s air pressure. Set it as per the air pressure mentioned in the datasheet.
10. Check the instrument air tubing leak. If the leak is there then attend to the leakage.
11. Check the actuator for passing. If it is passing then attend it by replacing it or overhauling it.
12. Check the valve by giving direct air. The body might be stuck. Rouse it a few times. This might solve the issue.
13. Drop the valve if it is still not operating and do an overhauling.

EndNote

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