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SOP for Calibration of Magnehelic Gauge

To lay down a Procedure for Calibration of Magnehaulic Gauge.

This Procedure is applicable for the Calibration of the Magnehaulic Gauge to be calibrated at Pharmasky Ltd.

  • Officer / Executive Engineering shall be responsible for the execution of this procedure.
  • Engineering Manager shall be responsible for the implementation of this SOP.
  • Head QA/designee shall be responsible for the compliance of this SOP.

Dimensions: 4-3/4 dia. x 2-3/16 deep.
Weight: 1 lb. 2 oz.
Finished: Baked dark gray enamel.
Connections: 1/8 NPT high and low-pressure taps, duplicated, one pair side and one pair back.
Accuracy: Plus or minus 2% of full scale, at 70°F. (Model 2000-0, 3%; 2000-00, 4%).
Pressure Rating: 15 PSI (0,35 bar)
Ambient Temperature Range: 20° to 140°F (-7 to 60°C).
Standard gage accessories include two 1/8 NPT plugs for duplicate pressure taps, two 1/8 NPT pipe thread to rubber tubing adapters, and three flush mounting adapters with screws.
Caution: For use with air or compatible gases only.
For repeated over-ranging or high cycle rates, contact factory.
Not for use with Hydrogen gas. Dangerous reactions will occur.


  • Master instruments used for calibration should be calibrated and should have its calibration certificate.

Procedure for Calibration
  • Both the Calibration Standard and the Unit under Calibration (UUC) shall be allowed to stabilize at the ambient conditions for at least 15 minutes or the warm-up period recommended by the manufacturer, whichever is more.
  • The UUC shall be properly cleaned & physically inspected for any breakages & deterioration.
  • Appropriate Calibration Standard shall then be selected for calibration.
  • The high-pressure port of the Calibration Standard and the UUC shall be connected to the corresponding port of Calibration Equipment by using appropriate fittings.
  • The low-pressure port of Calibration Standard and UUC shall be maintained at some arbitrary constant pressure to avoid the effect due to changes in ambient pressure conditions.
  • It shall be ensured that there is no leakage in the calibration system i.e., Low-Pressure Pump, Calibration Standard & UUC.
  • Zero setting of the Calibration Standard shall be checked & confirmed.
  • Performance of the UUC shall be checked by applying full-scale pressure by forwarding displacement of the piston (Clockwise rotation). In case of vacuum range performance shall be checked by applying full-scale vacuum by backward displacement of the piston (Anti-clock wise rotation).
  • While doing so the indication shall be observed for confirmation of the smooth functioning of the UUC.
  • The temperature and humidity conditions shall be noted.
  • The scale of the UUC shall be divided into a minimum of 4 points or as per the client's specifications.
  • When the whole system is ready desired pressure shall be delivered to the Calibration Standard and the UUC from the Calibration Equipment in an ascending and then in descending order at the same points.
  • It every point, the UUC shall be lightly tapped (in the case of analogue gauge).
  • The desired set readings on UUC shall then be compared with that of the Calibration Standard & the observations shall be recorded in the calibration data sheet only after attaining the pressure stability.
  • If the observed readings do not comply with the specified accuracy of the UUC, then zero and span settings shall be done by applying respective pressures to the Calibration System and repeating the steps as mentioned above & the observations shall be recorded in the calibration data sheet.
  • After the calibration is over, some time shall be given for the ‘Zero’ of the UUC to stabilize.

SOP : Standard Operating Procedure
ER : Engineering
No : Number
QA : Quality Assurance
UUC : Unit Under Calibration

Annexure-1 - Calibration Data Sheet

Revision History

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