When troubleshooting pressure switches in an industrial process area, applying a methodical approach is necessary in order to effectively identify and manage any problems that may occur. A step-by-step procedure is as follows:
Safety Precaution
Before starting any work, ensure that you have the necessary work permit as per site safety regulations. This may involve obtaining a hot work permit if there’s a potential for sparks or flames during the troubleshooting process.
Before handling the pressure switch, isolate power sources to the equipment by switching off the relevant circuit breakers or disconnecting power cables. Lockout/tagout procedures should be followed to prevent accidental re-energization.
Always wear the appropriate personal protective equipment (PPE) for the task at hand. This may include safety glasses, gloves, ear protection (if working in a noisy environment), and any specialized equipment required for the specific task.
Ensure that you’re working on the correct pressure switch by verifying its tag number against the work order or maintenance schedule. Cross-checking the tag number helps prevent errors and ensures that you’re troubleshooting the right equipment.
Consider the broader process safety implications of working on the pressure switch. If the switch is part of a critical system, consider whether any process modifications or shutdowns are necessary to ensure the safety of personnel and equipment.
If the pressure switch is located in a system containing pressurized fluids or gasses, take appropriate precautions for product venting. Before opening any connections or removing components, ensure that the system is safely depressurized to prevent releases that could endanger personnel or cause environmental damage.
Implement lockout/tagout (LOTO) procedures to ensure that the pressure switch cannot be accidentally activated while you’re working on it. Use lockout devices and tags to physically prevent operation and communicate the status of the equipment to other personnel.
Whenever possible, use the buddy system, especially when working in hazardous environments or performing tasks with elevated risks. Having a colleague present can provide an extra layer of safety and assistance in case of emergencies.
Familiarize yourself with the site’s emergency response plan and know the location of emergency exits, first aid stations, and emergency equipment such as fire extinguishers and eyewash stations.
Ensure that all personnel involved in troubleshooting pressure switches have received adequate safety training and are familiar with relevant safety procedures and protocols.
Tools Required for Pressure Switch Troubleshooting
When troubleshooting pressure switches, having the right tools at your disposal is crucial for accurate diagnosis and efficient resolution. Here are the essential tools you’ll need
Calibrated Pressure gauge for comparing system pressure
Multimeter
Data logger
PPE
Standard tools
Lockout/tagout devices
Understand the System and Type of Pressure Switch
Begin by thoroughly reviewing all available documentation pertaining to the industrial process and the pressure switch. This includes equipment manuals, wiring schematics, p&id, operating procedures, and maintenance records.
Clearly understand why the pressure switch is integrated into the system. Determine its primary function, whether it’s monitoring pressure levels, controlling equipment operations based on pressure thresholds, or ensuring safety interlocks.
Learn more about the function of the pressure switch in relation to the wider industrial process. Recognize the effects it has on equipment or processes upstream and downstream, any crucial dependencies, and any potential risks.
Determine the specific type of pressure switch installed in the system, whether it’s mechanical, electronic, differential, or another variant. Understanding its underlying principles of operation, unique features, and potential limitations is essential for effective troubleshooting.
Investigate whether any modifications or upgrades have been made to either the system or the pressure switch since its initial installation. Changes in configuration or settings may have implications for its behavior and troubleshooting requirements.
Visual Inspection
During visual examination, this below-structured approach systematically identifies potential issues and provides associated remedies to properly solve them.
Visual Inspection
Possible Cause
Remedy
Pressure Switch Housing
Cracks or damage to housing
Replace pressure switch unit or repair if feasible
Electrical Connections
Loose or corroded electrical connections
Tighten connections or clean/replace corroded components
Pressure Connections
Leaks at pressure connections
Tighten fittings or replace seals/gaskets
Mounting Hardware
Loose mounting hardware
Tighten mounting screws or bolts
Environmental Factors
Presence of contaminants (dust, debris, moisture)
Clean and protect the pressure switch from environmental hazards
Problem No.1 Setpoint Shift
Possible Cause
Remedies
Permanent deformation of the sensitive element due to fatigue or non-tolerated overages.
Recalibrate or replace the sensitive element.
Variation of the elastic features of the sensitive element due to its chemical corrosion
Recalibrate or replace the sensitive element with another made of a suitable material. If necessary, apply a fluid separator.
Problem No.2 Poor Repeatability
Possible Causes
Remedies
Wear of sealing components (e.g., O-rings)
Replace worn sealing components. Recalibrate the system after replacement.
Presence of air bubbles or condensation in the system
Remove air bubbles or condensation from the system. Modify the process connection line if necessary.
Problem No.3 Slow response
Possible Causes
Solutions
Blockage or obstruction in the connection line
Ensure the line is clear by checking and cleaning it.
Partially closed root valve
Open the valve fully to allow proper fluid flow.
Use of highly viscous fluid
Install a suitable fluid separator to improve instrument performance.
Incorrect pressure setting
Check the pressure setting.and Reset the pressure setting.Ensure the detected pressure and set pressure values are not too close and adjust the pressure setting value to ensure it’s not too close to the detected pressure.
Problem No.4 No Actuation of Pressure Switch
Possible Issues
Solutions
Root valve is closed
Ensure the valve is fully open.
Microswitch contacts are damaged
Replace the malfunctioning microswitch.
Electrical connections are loose
Check and tighten all electrical connections for secure fitment.
Interruption or short circuit in electrical line
Inspect the electrical line thoroughly for any interruptions or short circuits.
Problem No.5 Unintended Triggering of Pressure Switch
Possible Causes
Remedial Actions
Accidental shocks or excessive vibrations
Consider modifying the mounting to mitigate these effects.
Problem No.6 Pressure Switch Operation is Unstable.(Chattering)
Possible Causes
Remedial Actions
Pressure source fluctuation, small hysteresis, or short response time
Check the set pressure (hysteresis). Check the hysteresis value and adjust to correct band.
Incorrect wiring or broken lead wire
Check the power supply wiring. Correct the wiring. Check for bending stress on lead wire. Correct wiring conditions (reduce tensile force, increase bending radius
Incorrect settings
Review the set pressure to ensure it is appropriate for the application. Check the hysteresis range to ensure it is not too narrow, which can lead to frequent switching. Verify the response time setting at the initial configuration.
Instantaneous rapid system pressure fluctuation
Check for peaks and valleys of surges exceeding the actuation value of the switch. Install a surge damper on the switch to mitigate rapid pressure fluctuations. Alternatively, replace the current pressure switch with one having a larger actuation value.
Mechanical vibration of switch
Change the position of the switch to a location less affected by vibration. Install a shock mount or vibration isolation system to reduce unwanted actuation.
Pressure switch failure
If all other troubleshooting steps fail, consider replacing the pressure switch unit.
Problem No.7 Output Remains ON
Possible Causes
Remedial Actions
Incorrect pressure setting
– Check the set pressure. – Verify the operation mode, hysteresis, and output type (hysteresis mode/window comparator mode, normal/reversed output). Reset the pressure setting if incorrect. Reset the function settings.
Pressure switch failure
Replace the product if all other troubleshooting steps fail.
Problem No.8 Output Remains OFF
Possible Causes
Remedial Actions
Incorrect wiring
Check the wiring of the output. Correct any wiring issues found. Check that the load is connected in the appropriate manner.
Unsuitable model selection
Review if PNP is used when NPN should have been selected, or vice versa. – Review the selected model (output type).
Broken lead wire
Check for any bending stress on the lead wire. Ensure proper bending radius and minimize tensile force applied. Correct the wiring conditions by adjusting the tensile force and increasing the bending radius.
Pressure switch failure
Replace the pressure switch if all other troubleshooting steps fail.
Problem No.9 Will not Actuate at Desired Pressure
Possible Causes
Remedial Actions
Desired setting out of switch range.
Replace the bourdon tube or pressure capsule with the appropriate range.
Switch not set at proper pressure.
Readjust switch
Defective switch element.
Replace switch element.
Over stressed or fatigued pressure sensing element.
Replace pressure capsule.
Loose adjusting screw or bracket.
Replace or tighten.
Surplus electrical leads interfering with switch action.
Remove surplus from area around switch element.
Surge pressures in system exceed proof pressure of switch.
Replace pressure capsule, bourdon tube, or switch with proper proof pressure.
The calibration of the pressure switch is incorrect.
This checklist provides a systematic approach to troubleshooting pressure switch issues in industrial settings. By identifying potential problems and implementing appropriate mitigation strategies, you can ensure the reliable operation of pressure switches within your processes.
You can download and customize this checklist by below for your specific needs, ensuring efficient troubleshooting and maintenance of pressure switches in your industrial process areas.
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
