What does “out of class” mean?
A manometer is out of class when its indication error exceeds the maximum accuracy allowed by its class (1.0, 1.6, 2.5, etc.), generating unreliable measurements for process control, safety or quality.
Procedure to determine if the pressure gauge is out of class
The only reliable way to determine if a gauge is out of class is to perform a calibration. This process involves comparing the pressure gauge readings with those of a reference instrument (standard) that has a higher or known accuracy. Subsequently, the deviation between both readings must be evaluated and contrasted with the maximum error allowed according to the accuracy class of the manometer.
In the event that the deviations observed during calibration are greater than the maximum error accepted for the specific class of the manometer, it is concluded that the equipment is out of class and therefore does not guarantee reliable measurements.
But there are also warning signs and/or situations:
- Error at zero
The needle does not return exactly to 0 without pressure applied. - Unstable readings
The needle vibrates, sticks, or responds slowly. - Previous shocks or vibrations
Mechanical impacts can deform the internal mechanism. - Exposure to overpressure
If it exceeded 100–130% of the nominal range, permanent damage may occur. - Calibration interval expired
If you have already exceeded the period defined by your metrological plan, the risk of error increases.