SOP for In-house Calibration

Purpose

The purpose of this procedure is to provide general directions for In-house Calibration

Scope

This procedure covers the calibration of gauges and inspection fixtures.

Responsibilities

• It is the responsibility of the Head of Quality to ensure that this procedure is followed correctly.
• No changes may be made to this instruction without the authorization of the Head of QA.

Procedure

In-house Calibration

General

• Qualified personnel shall perform the calibration of gauges. Minimum Diploma in Mechanical Engg. with six months of experience in the calibration, the area shall be considered as qualified or in the supervision of calibration in charge.
• The temperature and humidity of the calibration room will be maintained as Temp: 22±2°C and Humidity 50 ±10%.
• Soaking of the gauge shall be carried out at the calibration room for about half an hour minimum.
• Visual checking shall be carried out for all kind of damages or any markings over the gauge.
• For all standard gauges, IS 3455 standards will be referred to decide the wear limits.
• For all special gauges, respective gauge drawings will be referred to decide the wear limits.
• For individual pin gauges ±0.005mm is the acceptance criteria
• For parallel blocks, IS: 2949 - 1992 standard will be referred to decide the wear limits
• For Surface Granite Block, IS: 7327 - 1991 standard will be referred to decide the wear limits.

Method of Calibration

Plug Gauge, Pin Gauge and Width Gauge

• Ensure only calibrated digimatic micrometer / 1-micron plunger dial is used.
• Ensure that the above digimatic micrometer/micron plunger dial is used only for calibration purposes.
• Clean the base of the Dial stand
• Select the suitable size of the Slip gauge of “0" Grade.
• Ensure proper wringing of Slips (Use a Minimum number of slips).
• Set the slips with only 10-20 micron pressure on the plunger dial.
• Measurement shall be taken at different places of gauge.
• Record the observation in the calibration report / History card.
• Compare the measured values against the wear limits for deciding the status.

Snap gauges

• Use VMS / Bore gauge for calibration.
• Measurements must be taken at different places of gauge.
• The actual size of a gap is defined as the perpendicular distance between the gauging surfaces.
• Record the observation in the calibration report / History card.
• Compare the measured values against the wear limits for deciding the status.

Ring gauges

• Use VMS / Bore gauge for calibration.
• Measurements must be taken at different places of gauge.
• Record the observation in the calibration report / History card.
• Compare the measured values against the wear limits to decide the status.

Receiver Gauges & inspection fixtures (position, pitch, distance, profile gauges, depth gauges etc.)

• The receiver gauges shall be calibrated as per the gauge drawings using Height gauge /VMS/1-micron plunger dial or appropriate instruments.
• In receiver gauges the gauge pins, width gauges, holes & slots shall be calibrated and measurement must be taken at different places of gauges.
• Record the observations in the calibration report / History card.
• Compare the measured values against acceptable wear limit and decide the status.

ALSO READ: SOP for Preventive Maintenance of Laboratory Instrument

Feeler gauge/Thickness gauge

• Ensure only calibrated digimatic micrometer / one-micron plunger dial is used.
• Measurements must be taken at different places of gauge.
• Up to ± 0.005mm deviation will be allowed from the basic dimension on all feelers.
• Record the values in calibration / history card and decide the status.

Dovetail gauges

• The Dove tail gauges shall be calibrated as per the gauge drawing by using calibrated “0” grade slip gauges, dig micrometer & measuring pins.
• Select the suitable size of measuring pins & “0” grade slip gauge (given in gauge drawing) for internal dovetail size measurement.
• Ensure proper wringing of slips are (use minimum no of slips).
• Use a dig-micrometer and a suitable size of measuring pins (given in gauge drawing) for External size measurement.
• Measurements must be taken at different places of gauge.
• Record the observation in a calibration card.
• Compare the measured values against the wear limits to decide the status.

Magnetic Parallel Blocks

• The parallel blocks shall be calibrated by using VMS
• Measurement must be taken on an entire plane by minimum of 10 points
• Recall the flatness of the face & Perpendicularity as well
• Measured values will be taken and monitored in the gage life monitor/ calibration history card
• IS: 2949 - 1992 standard will be referred to decide the wear limits

Granite Surface Plate

• The surface plate shall be calibrated by using VMS / Digital height gage
• Measurement must be taken on entire plane by min 20 points
• Recall for the flatness of the face & Perpendicularity as well
• IS: 7327 - 1991 standard will be referred to decide the wear limits

Environmental Instructions

• Cotton waste used for cleaning gauges should be disposed of in a designated bin.
• Ensure there are no oil spillages while calibration.
• Switch off the power in the standards room when not in use.

Health & Safety Instructions

• Ensure sufficient lighting in the area of calibration.
• Use gloves while handling instruments/gauges to prevent cuts or injuries due to sharp edges.
• While handling receiver gauges ensure there is no slippages. Always wear safety shoes while calibration.
• Wash with soap and water after calibration.
• If Isopropyl alcohol spills on the eye, immediately flush the eyes with water for at least 15 mins. Cold water may be used.

Annexure

Nil

Revision History

Nil

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