Troubleshooting Guide for DP Transmitters

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Just like every other equipment, DP transmitters can malfunction while in service. The ability to troubleshoot and locate the possible cause of malfunction of the transmitter is crucial for easy start up of the process the malfunctioning DP transmitter may have upset.
When troubleshooting DP transmitters, it is always valuable to consult the manufacturer’s manual for your DP transmitter. By so doing, you should be able to locate the malfunctioning parts of the transmitter and proffer a remedy immediately. However there are some problems that are common to most DP transmitters. If you suspect a malfunction, follow the guidelines below to verify that the transmitter hardware and process connections are in good working condition. Under each of the five common problems with DP transmitters, you will find specific guidelines/suggestions for solving the problem. It is wise to always deal with the most likely and easiest problems first.

Please follow the precautions below before and during troubleshooting of your malfunctioning DP transmitter:
1. Isolate the failed DP transmitter from its pressure source as soon as possible. Pressure that may be present could cause death or serious injury to technicians or personnel if the transmitter is disassembled or ruptures under pressure
2. Do not use higher than the specified voltage to check the transmitter loop. This may damage the transmitter electronics.
3. If there is need to open your DP transmitter while troubleshooting, please follow your manufacturer’s specific guidelines for dis-assembly of your transmitter. If you don’t serious injury or death to personnel may occur or your transmitter may be damaged.
The table below itemizes some common problems with DP transmitters and their possible remedies:

Problem	Potential Cause	Corrective Action
Low output or No output	Primary Element	Check the insulation and condition of primary element
	Loop Wiring	Check for adequate voltage to the transmitter Check the mA rating of the power supply against the total current being drawn for all transmitters being powered. Check for shorts and multiple grounds Check for proper polarity at the signal terminal Check loop impedance (should not exceed the specification for your plant) Check wire insulation to detect possible shorts to ground
	Impulse piping	Ensure that the pressure connection is correct.  Check for leaks or blockage.  Check for entrapped gas in liquid service. Check for sediment or debris in the DP transmitter process flange. Ensure that blocking valves are fully open and that bypass valves are tightly closed. Ensure that density of fluid in impulse piping is unchanged.
	Sensing Element	The sensing element is not field repairable and must be replaced if found to be defective.  Disassemble the transmitter and probe further(check your manufacturer’s manual for instructions on how to disassemble your transmitter;  Check for  any obvious defects. At this point you may need to contact your manufacturer if there is any defects in the sensing element
DP transmitter does not calibrate properly	Pressure source/correction	Check for restrictions or leaks. Check for proper leveling or zeroing of the pressure source. Check weights/gauge to ensure proper pressure setting. Determine if your pressure source has sufficient accuracy
	Meter	Determine if the meter is functioning properly
	Power Supply	Check the power supply output voltage at transmitter
	DP transmitter electronics	Make sure the transmitter connectors are clean. If the electronics are still suspect, substitute with new electronics.
	Sensing Element	The sensing element is not field repairable and must be replaced if found to be defective.  Disassemble the transmitter and probe further(check your manufacturer’s manual for instructions on how to disassemble your transmitter. Check for  any obvious defects. At this point you may need to contact your manufacturer if there is any defects in the sensing element
High Output	Primary Element	Check for restrictions at primary element
	Impulse piping	Check for leaks or blockage. Check for entrapped gas in liquid service. Check for sediment or debris in the DP transmitter process flange. Ensure that blocking valves are fully open and that bypass valves are tightly closed. Ensure that density of fluid in impulse piping is unchanged.
	Power Supply	Check the power supply output voltage at transmitter
	DP transmitter electronics	Make sure the transmitter connectors are clean. If the electronics are still suspect, substitute with new electronics
	Sensing Element	The sensing element is not field repairable and must be replaced if found to be defective.  Disassemble the transmitter and probe further(check your manufacturer’s manual for instructions on how to disassemble your transmitter;  Check for  any obvious defects. At this point you may need to contact your manufacturer if there is any defects in the sensing element
Erratic Output	Loop Wiring	Check for adequate voltage to the transmitter. Check for intermittent shorts, open circuits and multiple grounds
	Process Pulsation	Adjust damping
	DP transmitter electronics	Make sure the transmitter connectors are clean. If the electronics are still suspect, substitute with new electronics
	Impulse piping	Check for entrapped gas in liquid lines and for liquid in gas lines.