How to

Troubleshooting of I to P Convertor (Current to Pneumatic converter)

  • An I/P converter functions as a current-to-pressure transducer in industrial control systems, translating a 4- 20 mA current analog signal (I) into a 3 to 15 Psi pneumatic output (P). 
  • This converter is crucial for converting DC current signals into proportional pneumatic pressure, enabling the control of valves, dampeners, actuators, brakes, and clutches in industrial applications. 
  • It is worth noting that there are two main types of converters: I to P converters, which typically handle a 4-20mA signal, and E to P converters, which work with a 0-10V signal. While IP converters operate with current, EP converters function with voltage.
Step by Step procedure for Troubleshooting of I to P Convertor(Current To Pneumatic converter)
  • It is critical to ensure that all workers participating in the troubleshooting process have received extensive training and have a solid understanding of the specific I/P converter model and its associated systems.
  • Prioritize the use of suitable personal protective equipment (PPE), such as safety glasses and gloves, and ensure that the gear chosen is compatible with the potential hazards in the process area.
  • Before beginning any troubleshooting actions, it is critical to isolate the I/P converter via lockout/tagout methods, preventing unintentionally energization or pressure release during the diagnostic process inside the converter.
  • Take the hazardous area classifications inside the process environment into careful consideration, and use equipment that conforms with safety requirements related to potentially explosive or dangerous circumstances.
  • To reduce the risk of electrical short circuit, always turn off the power to the I/P converter before beginning any troubleshooting actions, and follow all approved safety protocols.
  • Release any leftover pneumatic pressure in the system to ensure a safe working environment and prevent unexpected releases during the inspection or disassembly of the I/P converter.
  • Conduct a thorough assessment of the I/P converter and its accompanying equipment, looking for apparent damage or signs of wear.
  • Follow the manufacturer’s directions and recommended troubleshooting techniques to the letter, consulting the technical documentation given for the specific I/P converter model.
  • Create clear and effective communication lines with other staff in the area, such as operators and maintenance teams, to relay information regarding ongoing troubleshooting activities.
  • In the event of unanticipated situations or issues during the troubleshooting process, familiarize yourself with and have quick access to emergency procedures, including protocols for emergency shutdowns.
  • Maintain proper ventilation in the work space to prevent the accumulation of harmful gasses or fumes, hence contributing to a safe troubleshooting environment.
ProblemPossible CausesSuggested Action
Reversed Current Polarity or Faulty Connections in input signal wiresCheck wiring and signal continuity with millimeter.Repair if faulty.
Broken Internal WiringCheck instrument resistance with ohmmeter.Correct as needed. Replace the faulty component.
No Air SupplyEnsure sufficient air supply.Isolation valve may closed.No air from the Regulator or regulator  may be faulty.Verify air supply and address any issues. Inspectand verify the the isolation valve in the instrument air line. Replace faulty regulator
ProblemPossible CausesSuggested Action
Insufficient instrument  supply air pressureCheck and adjust supply pressure to required Ensure an adequate supply pressure with instrument data sheet
Damaged Coil or Nozzle / orificeReplace the damaged component.Replace the damaged part.
Oil ContaminationInspect for oil contamination.Clean or replace affected parts.
Clogged RestrictorCheck and clear any blockage.Verify the air flow  or replace the restrictor.
Actuator or positioner faultyInvestigate if positioner or actuators are stuck open.Perform maintenance on  faulty components.
ProblemPossible CausesSuggested Action
Worm out or  Disengaged with Pinion (After Excessive Adjustment)Re-engage components.Ensure proper engagement of zero adjustment mechanisms.
Zero Calibration Error on Initial Turn-OnRepeat the exercise using the instrument multiple times.Recalibrate if necessary.
ProblemPossible CausesSuggested Action
Electrical Input SignalLoose wires or connections in input signals,  short circuit in the signal connections.Reconnect and secure wiring. Verify signal stability.
Liquid in Air SupplyCheck air supply for contaminationClean air supply or replace the filter  of regulator
Output Pressure same as Supply PressurePneumatic connections reversed.Supply and output both connected to input portEnsure supply is connected to the “IN” port.Verify output is connected to the “OUT” port.
Transducer generate reverse  outputWires connected in reverse.Check and correct the wiring connections.
Sluggish Performance or Reduced Range Plugged or blocked orifice /nozzleSupply pressure too lowRemove orifice /nozzle screw and clean orifice/nozzle with wire or pin Supply pressure must be at least 5 PSIG above the 100% output
Step by Step procedure for Troubleshooting of I to P Convertor(Current To Pneumatic converter) 1
ProblemPossible CausesSuggested Action
Excessive Supply PressureCheck and adjust supply pressure.Ensure supply pressure within specified range in output of regulator.
Damaged Diaphragm or Seal in Pneumatic relayInspect diaphragm or seals for damage.Replace damaged diaphragm or seals.
Calibration ErrorVerify calibration settings.Recalibrate I/P converter if necessary.
Electrical Signal ErrorCheck for erratic electrical signals.Inspect wiring and connections for issues.
Restricted Exhaust FlowCheck for blockages in exhaust path in the converter.Clear or replace any obstructed components.

Click here for Procedure for Calibration of I To P Converter 

ProblemPossible CausesSuggested Action
Fluctuating Output current signalInconsistent PLC signal.Verify and stabilize the signal from the PLC.
No Output Signal from PLCPLC signal not reaching the I/P converter.Check PLC programming and connections.
Incorrect Output ScalingMismatch between PLC output scaling and I/P converter input requirements.(4 – 20mA)Adjust scaling parameters in the AO card of PLC.
Faulty analog Output Cards in Control SystemMalfunctioning output cards in the control system.Diagnose and replace faulty output cards.
ProblemPossible CausesSuggested Action
Inconsistent Signal TransmissionFaulty signal isolator or fault in the connectionsInspect isolator or junction box for issues.
Signal InterferenceExternal electromagnetic interference.Shield or relocate the signal cables.
Broken Wiring ConnectionsDisconnected or damaged wires in the junction box.Check and repair wiring connections.
Voltage Drops or SpikesPower supply issues affecting the isolator.Verify the stability the power supply to the isolator.
ProblemPossible CausesSuggested Action
Oscillations in OutputIncorrect PID parameters.Reevaluate and retune PID parameters.
Slow ResponseProportional, integral, or derivative values that are not ideal.Adjust PID parameters for desired response.
Overreactions or Instability in the output.Aggressive PID settings.Fine-tune PID parameters for stability.
ProblemPossible CausesSuggested Action
Temperature FluctuationsAmbient temperature changes affecting the I/P converter.Install environmental controls or shielding.
Humidity or Moisture IssuesHigh humidity causing condensation or moisture ingress.Seal or protect equipment against humidity.
CorrosionExposure to corrosive substances.Implement corrosion-resistant control measures.
Vibration or Mechanical StressVibrations impacting I/P converter stability.Install vibration dampening or isolation. Otherwise relocate the i to p converter.

Cleaning the orifice of an I/P (current-to-pressure) transducer is crucial for maintaining accurate pressure regulation. Here’s a step-by-step guide on how to clean the orifice:

Step-by-Step procedure for Cleaning of  I to P Convertor Orifice:
  • Screwdriver set
  • Gauge pin or thin wire
    1. Before starting any maintenance, turn off the supply air to the I/P transducer to ensure safety.
    2. The orifice screw is typically located on the body of the I/P transducer and it can be found on the face of the unit below one of the calibration screws.
    3. Use a suitable screwdriver to carefully remove the orifice screw from the unit. Inspect the screw for any visible build-up or dust.
    4. Remove any present build-up on the screw. It’s essential to have a clear path for air flow.
    5. You will notice a very small hole on the side of the screw. This is the orifice.
    6. Use a gauge pin or thin wire to carefully run through the orifice hole. This helps clear any internal blockages that may be affecting the pressure regulation.
    7. Once the orifice is cleared, carefully reinstall the screw into the side of the unit. Ensure that it fits snugly but avoid over-torquing to prevent damage.
    8. If air is leaking past the screw when supply air is reconnected, tighten the orifice screw further until the leak stops. Be caution to avoid over-tightening.
    9. Refer to the instruction manual for troubleshooting instructions if you run into more problems or if erratic functionality persists. 
    10. By following these steps, you may keep your I/P transducer’s orifice clear, allowing for constant and accurate pressure adjustment. This type of regular maintenance will add to the unit’s optimal performance and reliability.

    If you’re dealing with a flapper nozzle type I/P (current-to-pressure) converter, the cleaning process involves some additional considerations.

    Cleaning an I/P Transducer with Flapper Nozzle
    1. Before starting any maintenance activities, turn off the supply air to the I/P transducer to ensure safety.
    2. Flapper nozzle type I/P converters have a flapper mechanism instead of a traditional orifice. Locate the flapper nozzle on the unit.
    3. Depending on the model, you may need to remove the cover of the I/P transducer to access the flapper mechanism. Use a suitable screwdriver to carefully remove the cover.
    4. Inspect the flapper mechanism for any visible blockage, debris, or obstruction. Use a soft brush or compressed air to gently clean the flapper and surrounding area.
    5. If the flapper nozzle has any visible blockages, use a gauge pin or thin wire to carefully clear them.Make sure there are no obstructions in the way of the flapper’s movement.
    6. After cleaning the flapper mechanism and nozzle, carefully reassemble the unit. Ensure that all components are properly aligned and secured.
    7. If you removed the cover, reinstall it properly using the screwdriver.
    8. Turn on the supply air to the I/P transducer and check its performance. Check for any signs of improper output or unexpected pressure output(calibration error).
    1. If the output is not within the expected range, refer to the unit’s manual for instructions on adjusting the flapper mechanism or other calibration settings.
    2. If you encounter persistent issues or need further guidance, refer to the instruction manual for troubleshooting specifics related to the flapper nozzle type I/P converter.
     Checklist For Troubleshooting Maintenance Of I To P Converter

    Click here for Procedure for Calibration of I to P Converter 

    Sundareswaran Iyalunaidu

    With over 24 years of dedicated experience, I am a seasoned professional specializing in the commissioning, maintenance, and installation of Electrical, Instrumentation and Control systems. My expertise extends across a spectrum of industries, including Power stations, Oil and Gas, Aluminium, Utilities, Steel and Continuous process industries. Tweet me @sundareshinfohe

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