Calibration of pressure switch using FLUKE 718 pressure calibrator

What is a pressure switch used for?

A pressure switch is a device that is commonly used to monitor pressure levels in various systems and applications. It can be found in many different kinds of equipment, such as air compressors, refrigeration systems, hydraulic systems, and many more. Its primary function is to ensure that the desired pressure level is maintained throughout the system or application.

How do you calibrate a pressure switch?

Purpose and scope:

The following process is used to calibrate the Pressure Switch using the FLUKE 718 Pressure Calibrator as a guide. Calibration of the Pressure Switch is completed in this manner.

Tools required for calibration of pressure switch:

• Necessary hand tools.
• FLUKE 718 Pressure Calibrator
• Tubes and Test Probes & Leads
• Soft Cloth for cleaning.
• Required standard fittings for tube connection

Safety 

• If you disconnect a pressure switch from the system it is linked to, the switch will no longer operate properly and will no longer produce pressure measurements or activate the system. 
• In a system where the pressure switch is a critical safety component that helps prevent damage or accidents from occurring, this has the potential to create problems or malfunctions in the system.
• In the event that you need to disconnect a pressure switch for the purposes of maintenance or repair, be sure to follow the appropriate procedures and take the necessary measures to prevent any accidents or damage to the system. 
• Before you disconnect the pressure switch, you need to make sure that the power supply has been turned off and that any pressure that may have built up in the system has been released.
• Please follow the link given below for information on fundamental safety and general guidelines as well as details on calibrating operations in process industries.

Basic Safety and General Consideration While Executing Calibration Process in process industries

• Ask the panel operator to set the interlock in manual mode for the trip logic and MOS for the ESD loop.
• Make sure the pressure switch is completely separated from the process.
• Once the equipment has been separated, make sure it is safe to work on by looking for any potential dangerous compounds or residual pressure.
• Always use the proper PPE, such as gloves, safety glasses, and a face mask, while working in a process area to protect you from hazardous chemicals and to maintain compliance with safety standards.
• Isolate the pressure switch signal contact’s control power from the nearby junction box or marshalling panel near the control room
• Close the pressure switch isolation valve and drain the trapped  process material from the impulse line.
• Close the pressure switch isolation valve, then unscrew the drain plug to release the trapped process material in the impulse line.
• In addition, be sure to get instruction on how to correctly disconnect the pressure switch from the equipment by consulting either the equipment documentation or an experienced technician.

Pressure switch calibration setup

• It can be necessary to attach a tube to a pressure switch in order to provide a reference pressure while calibrating it.
• The pressure switch’s pressure port should be identified. The tube will be attached at this point.
• It is necessary to carefully clean the pressure switch port and ensure that no process liquid is present. If it’s present, the calibrator will be harmed.
• Make sure the tube you’re using is the appropriate size and kind for the pressure range for which you need to calibrate the switch.
• Additionally, the tube has to be spotless and clear of any material that can tamper with the pressure measurement.
• One end of the tube should be connected to the pressure switch’s pressure port.
• To avoid any leaks, make sure the connection is tight and secure.
• The opposite end of the tube should be connected to the pressure source (fluke 718 pressure calibrator) that will provide the reference pressure.

How do you calibrate and adjust a differential pressure switch?

Calibration procedure

• Turn on the 718 pressure calibrator and wait for it to reach a stable level.
• Once the pressure reading is steady, you may start the calibration activity.
• Inspect the pressure switch to be calibrated and the FLUKE 718 Pressure Calibrator to make sure they are both in good condition.

• It’s important for zeroing the calibrator before using it to ensure its accuracy. To reset the pressure display to zero, push the zero button. Before pressing this button, release pressure to the atmosphere.
• Choose the pressure unit and the range needed for the pressure switch calibration when configuring the FLUKE 718 Pressure Calibrator.
• Turn on the Fluke calibrator, and then release the pressure from the vent valve. Please push the zero button to clear the zero offset at this time. And then you should shut the vent valve.
• Set the mode to “switch test mode” by pressing the switch test button. Connect the banana terminal of the Fluke calibrator wire probes to the Calibrator mA and COM terminals. Connect the other end of the probe to the pressure switch contact terminal (NO or NC).

• By using the instrument datasheet or specification documents, determine the pressure switch’s setpoint (set and reset value).
• Examine the switch’s present settings in scale of pressure switch to verify whether they are already within the appropriate pressure range before making any adjustments.
• Ensure that all of the connections are secured properly.
• Till the setpoint is achieved, gently increase the pressure using the hand pump.
• Now, using the FINE adjustment knob, adjust the pressure until the switch open or close.( contact change over)
• Once the switch is turned on, OPEN is shown. Bleeding should be done gradually until the pressure switch closes. On the monitor, RCL is displayed.
• To see the pressure readings for the switch’s opening, closing, and deadband, push the switch test button.
• For three seconds, hold down the switch test button to reset. To go to Test mode, press any other key and hold it for 3 seconds.
• Compare the measurements obtained during calibration to the pressure switch’s expected values. Adjust the pressure switch as needed if there are noticeable variances.
• To ensure that you are not exceeding the ideal set point, make small adjustments and check the pressure measurement after each one.
• The pressure switch setpoint should be adjusted until the switch contacts open and shut at the required pressure.
• Please read the manufacturer’s instructions before continuing since the calibration procedure may differ based on the particular pressure switch.
• Make a note of the pressure switch’s final configuration, including the set point as well as any changes that were made, and the date that the switch was calibrated.

Recording calibration

• Apply inputs that match the pressure switch’s set and reset points in the direction of rising and falling pressure from the test standards.
• Calibration must be done if the output value does not fall within an acceptable range. If all of the output values (+/-%) are within accepted limits, further calibration is not needed.
• Fill out the blank calibration report’s as found/as left column with the resulting output values.

Completion of calibration

• Once the calibration was done well, place the calibration label on the pressure switch.
• The calibrating setup has to be vented and depressurized.
• Disconnect the testing equipment.
• Make sure that workspace is clean.
• De-isolate the apparatus.
• Bring the signal that is being bypassed or inhibited back up to normal.
• Bring the pressure switch back online and back into operation.

Sample calibration report

The image that follows demonstrates that the pressure switch sample report of calibration was performed by using 718 calibrator.

The link below leads to a file that can be downloaded of the Excel template that was used to make the pressure switch calibration report.