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What is proof pressure?

ASME B40.100 Bourdon Tube Proof Pressure Definition
Proof pressure (often times called over pressure) is the maximum pressure a gauge can withstand without evidence of change in accuracy. Proof pressure may be a semi-destructive test and should not be conducted repeatedly on the same gauge. It may be expressed as a pressure or as a percentage of full scale.

Proof Pressures
1.5", 2" and 2.5" pressure gauges with ranges up to 600 psi have a proof pressure of 125% of span. For ranges above 600psi, the proof pressure is 110% of span.

Pressure gauges should not operate continuously at the proof pressure limits stated. The maximum continuous pressure a gauge should be subjected to is 75% of the gauge span per ASME B40.100.

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