We’ve got an important topic to discuss with you today: the overpressure protection option available on our T6500 XRA pressure gauge. Why is this option so important? Because it shields the instrument against overpressure buildup in the system – and can withstand overpressure up to four times the measurement portion of the range.

These gauges, also known as retard gauges, are excellent fits for process and industrial applications – particularly those where pressure spikes or overpressure beyond measurement portion of the pressure ranges can occur. An example is the opening or closing of a valve. Pipeline overpressure, faulty regulators, process components (compressor, reciprocating pumps) and other factors can also contribute to this.


Also known as a hydraulic transient, it is one of the common culprits of sudden surges in pressure. Commonly you’ll see an additional external pressure limiting device (or PLV) used to mitigate it, but with the new T6500’s overpressure protection option, the PLV may not be necessary. We’ve developed a product that makes this process less complex, and it also means fewer potential leak paths along with cost savings – and there’s a clearly-defined overpressure range on the gauge’s dial.


Let’s walk through the process. First, the overpressure mechanism restricts motion of the Bourdon tube beyond the measurement of the gauge dial range. In restricting that motion, the natural spring rate of the Bourdon tube with relation to pressure is altered, and allows the system to see high pressures that would otherwise damage the gauge.

There’s also unique dial artwork designed to identify two pressure regions; the first is the “measurement range,” which features the typical graduation and figure pattern seen on the standard T6500. Also, there’s a red band beyond the full-scale range with the word “overpressure” clearly displayed on the dial. This portion of the scale allows for pressures up to 400% of the gauge range.

The accuracy class of the measurement portion of the scale is ±1.0%. This section is the pressure region, which the gauge should typically operate. The second is the “overpressure range,” which is a simple visual indicator that the process pressure has exceeded the maximum working pressure intended for this instrument.

The final figure shown in this region is the maximum overpressure value that can be seen by the gauge. The proper range for your application should be selected similarly to a conventional pressure gauge, where the operating pressure should read mid-scale.

To choose the correct pressure gauge range for your process, you will need to consider the standard operating pressure of the gauge and the potential pressure spikes that may occur in the process. The T6500 gauge with the overpressure options can provide up to 400 percent over-range protection

Contact ESP for all your pressure guage & tramitter needs!