Common issues in a process plant
After 1 year of troubleshooting instruments issues in my factory, I realized there are only a few key reason why field instrument fail :
- Vibration
- Heat
- Humidity / Water
- Dust
These faults, all in all, originated from design phases, where installation details, process data are overlooked.
- Vibration
- Heat
- Humidity / Water
- Dust
These faults, all in all, originated from design phases, where installation details, process data are overlooked.
Vibration
It's very common in a process plant where vibration is generated, by choice or by nature. Nevertheless, it's one the the main major cause for electronics to fail. Vibrations breaks electronics soldering, cable joints, cable connection, loosing screws here and there.
In my plant, I have encounter:
-Level switches failed due to vibration from air knocker or shifter.
- Pressure switches failed due to M12 cable connection failed.
- Coriolis flowmeter, transmitter side, failed during operation due to installed on a vibrating platform
- a whole set of servo controllers and drivers failed intermittenly due to cabinet and cable supports are put next to major vibration forces
- a stack of temp. transmitter and conductivity transmitter failed on a high flow - high vibration pipeline
Solution:
- Install remote type of instrument if possible. It will separate the vibration source from all the electronics, thus, prevent this trouble. Take special note on the instrument support.
- If there is no choice but to install the instrument near the vibration source, pick one that is rated for the vibration. Install cable loosely, and above all, stock enough spares for replacement.
In my plant, I have encounter:
-Level switches failed due to vibration from air knocker or shifter.
- Pressure switches failed due to M12 cable connection failed.
- Coriolis flowmeter, transmitter side, failed during operation due to installed on a vibrating platform
- a whole set of servo controllers and drivers failed intermittenly due to cabinet and cable supports are put next to major vibration forces
- a stack of temp. transmitter and conductivity transmitter failed on a high flow - high vibration pipeline
Solution:
- Install remote type of instrument if possible. It will separate the vibration source from all the electronics, thus, prevent this trouble. Take special note on the instrument support.
- If there is no choice but to install the instrument near the vibration source, pick one that is rated for the vibration. Install cable loosely, and above all, stock enough spares for replacement.
Heat
OMFG, I can't believe that our major instrument supplier said that a compact type instrument with Temp. Ambient rating of 80oC is suitable for a process of 95oC. The heat transfer directly from the Pt100 to the transmitter and fail it so frequently, we have a box of broken transmitter. Well, the Pt100 survived though.
On another hand, I have proximity switch in a high temperature dryer (up to 160oC) frequency failed. The rated temperature for that switch is 80oC, with maximum possible is only 120oC
Solution:
- Read carefully on the temperature requirement of instrument and select the right type.
- Pick remote type if budget allow
On another hand, I have proximity switch in a high temperature dryer (up to 160oC) frequency failed. The rated temperature for that switch is 80oC, with maximum possible is only 120oC
Solution:
- Read carefully on the temperature requirement of instrument and select the right type.
- Pick remote type if budget allow
Water, humidity, dust
Those 3 killers can be prevented easily if done right:
- Everything must be IP66 and above for field installation
- Cable glands must be metal and sized correctly. I have seen so many wrongly size glands, thus can't do anything to prevent water
- Do note and check on spare glands. Spare glands must be plugged properly
- Everything must be IP66 and above for field installation
- Cable glands must be metal and sized correctly. I have seen so many wrongly size glands, thus can't do anything to prevent water
- Do note and check on spare glands. Spare glands must be plugged properly