Preventive maintenance(PM) procedure for Bubbler system level measurement

A typical method for determining the level of liquids in tanks, containers, or open channels is the bubbler method level measurement. The process entails creating a stream of bubbles at the liquid’s bottom and measuring the pressure necessary to do so. The depth of the liquid has an impact on the pressure needed to produce bubbles.

Preventive maintenance(PM) procedure for Bubbler system level measurement 1

The accuracy and dependability of level measuring systems using the bubbler method depend on preventive maintenance. The following job list includes explanations for each task to assist maintenance technicians recognise the significance of each task and carry it out on a regular basis.


  • Request that the panel operator set the MOS (maintenance override switch) for the ESD loop and manual mode (bubbler method level control loop) on the controllers respectively.
  • Before beginning any PM activities, it is necessary to simultaneously configure above both of these parameters
  • Find the level transmitter that uses the DP type bubbler method for PM maintenance.
  • Make sure the level transmitter is a bubbler technique DP type, and note and double-check any important details like the Tag number.
  • Depending on the kind of system, you might need to depressurize both the bubbler method level transmitter and the system’s impulse tubes before PMing the bubbler method level transmitter.
  • Use the necessary techniques to depressurize the system (such as turning off the purge gas supply or main purge air inlet pressure of the instrument air header).
  • Turn off the level transmitter’s power and locate the power supply source for isolation by using an instrument loop diagram to look for any nearby junction boxes or Marshalling Cabinets close to the control room.
  • Depending on the equipment and process location of the bubbler technique level transmitter, this procedure may need to be modified.
  • When using bubbler method level DP type level transmitters or other process equipment, always adhere to the manufacturer’s instructions and local safety regulations.
  • To stop inadvertent starts, adhere to lockout/tagout policies. For preventative maintenance, keep the bubbler technique DP-type level transmitter out of the process.

Preventive maintenance tasks

Task-1: Inspection of bubbler tube

  • The main element of the bubbler system that produces bubbles at the liquid’s bottom is the bubbler tube.
  • The bubbler tube may clog up with debris or scale over time, limiting gas flow and compromising measurement accuracy.
  • Maintenance technicians can keep gas flow and bubble formation at the desired levels by routinely examining the bubbler tube for obstacles and clearing them away.
  • Remove the cleanout plugs, push a rod through the tubes, and/or flush with a suitable liquid if there is a propensity for particles to crystallize in the bubble tubes or if debris tends to gather.
Preventive maintenance(PM) procedure for Bubbler system level measurement 2

Task-2: Check purge air or gas supply

  • The pressure necessary for the bubbler system to produce bubbles is provided by the gas or air supply.
  • To avoid jams in the bubbler system, it is crucial to confirm that the gas or air supply is pure, devoid of impurities, and correctly filtered.
  • In order to make sure that the gas or air supply pressure and flow rate are within the acceptable range for the bubbler system, maintenance technicians need additionally verify them.
  • Examine the air pressure regulator’s and the air flow regulator’s (rotameter) physical condition. 
  • As stated in the installed bubbler method transmitter data sheet, verify the pressure and flow set parameters.
Preventive maintenance(PM) procedure for Bubbler system level measurement 3

Task-3: Inspect pressure transmitter

  • The back pressure from the bubbler system tubes is measured using a pressure transmitter.
  • The accuracy and dependability of the pressure transmitter may be impacted over time by damage or corrosion.
  • Maintenance technicians are able to identify problems with the pressure transmitter and fix them before they result in inaccurate measurements by performing routine inspections.

Task-4: Check the tubing for leaks

  • Purge Gas or air loss and measurement accuracy can also be impacted by bubbler system leaks.
  • Regular leak checks should be done by maintenance technicians, especially around fittings and connections.
  • Any identified leaks should be fixed right away to stop gas loss and measurement errors.

Task-5: Calibration in regular interval

  • Technicians should calibrate the bubbler method level measurement system on a regular basis, in accordance with the manufacturer’s recommendations or industry best practices.
  • Calibration entails comparing the measured pressure with a known reference pressure and adjusting the transmitter to ensure that the measurements are accurate.
  • Refer the below link for the calibration procedure for the Bubbler system level transmitter.

Calibration procedure for bubble method level measurement system

Task-6: Check the integrity of the electrical connections

  • The bubbler level measurement system depends heavily on its electrical connections and cabling in order to function properly.
  • The accuracy and dependability of the system may suffer as a result of the wires wearing out or becoming damaged over time.
  • Maintenance technicians can identify and fix any faults with the electrical connections if they do routine inspections of the connections on a regular basis. This helps in ensuring that reliable measurements are obtained. 

Task-7: Environmental conditions

  • Temperature and humidity levels in the environment might have an impact on the measurement’s accuracy.
  • The bubbler system must be put in a stable area free from sources of heat or humidity, according to maintenance technicians.
  • In order to guarantee that the ambient conditions stay within the acceptable range for the bubbler system, they need also frequently check them.

Task-8: Documentation

  • For the purpose of troubleshooting and identifying trends in the system’s performance, it is crucial to keep precise records of all maintenance tasks, calibration dates, and any problems or repairs that are made on the system.
  • Maintenance team should keep track of this data in a logbook or database so that it is available for analysis and reporting.

Completion of PM maintenance

  • After the PM is finished, clean the tools and equipment, store it safely, and make a note of the information from the PM check list for later use.
  • Verify that the PM’s workspace has been maintained tidy.
  • After the PM, de-isolate the apparatus and restore normal air pressure to the instrument air header or purge gas supply system.
  • Restore the bubbler type level measurement system’s bypassed or inhibited signal to its initial level.
  • Before using the bubbler type level measurement system, make sure it is in good working order.

Preventive maintenance checklist

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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