Max Process Temperature of Pressure Gauges

It will vary from manufacturer to manufacturer and from gauge range to gauge range. So the original equipment manufacturers are the people to talk to in the first instance.

Given the possibility of parallax errors while reading the gauge, +/-1%FSD sounds rather ambitious.

Pressure Gauge Handbook, by Philip W. Harland, Ametek, 1985

Chap. 6 Gauge Selection and Installation pg 174

6.3 ENVIRONMENTAL CONDITIONS

6.3.1 Environmental Considerations

There are many environmental conditions that will affect the accuracy and life of a gauge. These include temperature, vibration, mechani­cal shock, humidity, corrosive atmospheres, and dust.

6. 3.2 Effect of Temperature—Range Shift

One of the most important environmental considerations is the effect of ambient temperature. In addition to ^possible deterioration of the soft soldered joints in the pressure-containing envelope, the accu­racy may be adversely affected. This loss of accuracy is the result of two distinct physical changes. The first of these is a change in the modulus of elasticity of the bourdon (change in spring rate). The change in spring rate causes a "range shift," resulting in er­rors which increase proportionally as the pressure is increased. The error resulting from the spring rate change may be as much as 2% of the indicated reading for each 100°F increment of temperature change. Therefore, a gauge with a span of 0—100 psi that was cali­brated at 75°F might have added errors at a temperature of 175°F equal to +2 psi at 100 psi indication and +1 psi at 50 psi indication. If the initial accuracy of the gauge was 1% of full scale, then the er­rors at 175°F might be 3 psi at 100 psi indication and 2 psi at 50 psi indication.

6. 3.3 Effect of Temperature—Zero Shift

Temperature extremes introduce an additional error called "zero shift," which is caused by the physical change in the dimensions

in the various parts of the gauge with temperature. The magnitude and direction of this error vary with gauges of different designs and are functions of the relative thermal expansion of all of the va­rious parts of the gauge, involving materials, methods of attachment, and dimensions. Zero shift is a constant shift over the entire scale regardless of whether or not pressure is applied to the gauge, and the magnitude of the shift does not vary with applied pressure as it does with range shift.

6.3.6 Maximun Temperature Limits

The maximum ambient temperature normally considered parctical, even with temperature compensation, is 250°F

Different mfg's will have different specs as far as ambient temps go. When installing such a gauge be sure to use a "pigtail" set perpendicular to the pipe it is mounted on - if it is on a pipe. Edmund

I was going to make the same recommendation but will add one more "watch-out".

Since you are concerned about temperature impact, it is likely that the pipe / line being measured is HOT. Therefore, an thing mounted above that system will also be "heated" by the temperature loss of the line. Mount your gauge after a 90 and nipple long enough to pass edge of line before another 90 (up) to the pigtail and gage cock before the gauge. On a large pipe / line, support the horizontal nipple with wood block trimmed to match line curve or similar device.