CALIBRATION OF COMPOUND GAUGES

1.0    PURPOSE:
    
    To describe a standard operating procedure for the calibration of compound gauges.
    
2.0    SCOPE:
    
    The standard operating procedure describes in detail the method for the calibration of compound gauges in the plant.
    
3.0    RESPONSIBILITY:
    
    The  responsibility of  calibrating the gauges lies with the staff of rank not lower than the supervisor of maintenance department.
    
    The responsibility of preparation, review and approval of the standard operating procedure lies with the Manager (Maintenance), Head of  Production and Head of   QAD respectively.
    
4.0    METHOD:
    
4.1    Compound gauge contains both pressure and vacuum gauges.
    
4.2    In the compound gauge, pressure gauge shall be calibrated as per the procedure.
    
4.2.1    Select suitable range of standard pressure gauge, calibration traceability with National Physical Laboratory or their authorized laboratory.
    
4.2.2    Use comparison test pump to calibrate the pressure gauge in the compound gauge.
    
4.2.3    Fix the standard gauge on one side of the comparison test pump and the gauge which is to be calibrated on the other side of the comparison test pump.
    
4.2.4    Apply the pressure by rotating the wheel clockwise, which is provided on the comparison test pump.
    
4.2.5    Note down the pressures displayed by standard gauge and the gauge which is to  be calibrated at different pressures from minimum to maximum range of the gauge.  Record the readings in the format xxxxx shown in Annexure-I.  
    
4.2.5    Acceptance criteria:
    
The resolution of gauge shall be considered as acceptance criteria for that particular gauge.
?    If the gauge is graduated with 0.1 Kg/cm2 resolution, the acceptance criteria shall be 0.1 Kg/cm2.
?    If the gauge is graduated with 0.2 Kg/cm2 resolution, the acceptance criteria shall be 0.2 Kg/cm2.
?    If the gauge is graduated with 0.5 Kg/cm2 resolution, the acceptance criteria shall be 0.5 Kg/cm2.
    
4.3.    In the compound gauge, vacuum gauge shall be calibrated as given below.

    
4.3.1    By using conversion formulae (1" of Hg = 25.4 mm of Hg, Kg/M2 = 760 mm of Hg) make the conversion table as shown in Annexure-V shall be considered while calibrating the vacuum gauge.
    
4.3.2    Fix a manometer and the gauge to be calibrated to the manifold, compare the two by applying vacuum.
    
4.3.3    Note down the vacuum readings displayed by manometer and the gauge which is to be calibrated at different vacuum from minimum to maximum range of the gauge.  Record the readings in the format xxxxx shown in Annexure-I. 
    
4.3.4

    Acceptance criteria:

Compound Gauge range (for vacuum)       Acceptance criteria
 
   0    to   760 mm Hg                                         ±  10 mm Hg
   0    to   30” of Hg                                            ±  4” of Hg
   0    to   -1 Kg/cm2                                            ±  0.2 Kg/cm2
    
4.4    Whenever the gauge is rectified or replaced with another before the scheduled calibration due date, the same shall be informed to the QAD.  Recalibration data shall be recorded as per format xxxxx shown in Annexure-II and also entered in the history card of the gauge.
    
4.5    The recalibration format xxxxx is also shall be used whenever the gauges calibrated for validation purpose.  The same shall be remarked in remarks column.  
    
4.6    During the calibration, if the Compound gauge (Pressure / Vacuum) does not meet the acceptance criteria, service the gauge, recalibrate and then inform to the QAD for taking necessary action regarding variation of the quality and yields of the batches carried out with that instruments.    If the instrument is not possible to repair inside the premises, send it to the outside agency for necessary repairs.  If the instrument is not serviceable even at out side agency scrap the instrument.    
    
4.7    Apart from this recalibration, the calibration shall be followed as per regular schedule.
    
4.8    Calibration tag for compound gauge shall be tied to the gauge with the following particulars. (whenever there is no  error in the gauge, white  coloured  tag   shall  be  tied to the gauge.  If there is an error and it is with in the acceptable range,  pink coloured tag shall be  tied  to  the gauge).

4.9    Frequency: Calibration shall be once in two months ± 2 days.
    
5.0    RECORDING:
    
    The responsibility of recording the calibration readings as per Annexures lies with the staff of rank not lower than supervisor of maintenance department.

Compound gauges, engineering,