When gauges are used with steam or other high temperature processes several options should be considered as follows:

Brass Internals Gauge

It is generally accepted that the maximum temperature inside the sensing element of a brass internals gauge should not exceed 150º F.  This temperature limit is based on the fact that a lead tin solder (soft solder) is commonly used to seal the tip and socket on a bourdon tube type gauge with brass internals.  At higher temperatures these joints may loose their strength and fail.  We use soft solder on brass internals in pressure ranges below 800PSI and silver braze all internals above this as standard.

Brass Internals Gauge (Silver Brazed)

On special orders McDaniel Controls can supply gauges with brass internals below 800PSI with silver brazed, however, a price adder would apply.  The advantage silver braze would offer will be a moderately higher process temperature limit of 250ºF maximum.

Use gauges with of 316 Stainless Steel internals

Use of pressure gauges with 316 Stainless Steel internals limits need for concern due to high temperature applications.  Gauges with  316 Stainless Steel internals are argon arc welded and the above temperature limits would not apply.

Use of a siphon or pigtail

A siphon or pigtail can be used to trap condensed steam or other vapor and to further isolate the gauge from the heat source.  This makes a liquid seal in the line to the gauge and prevents the high temperature from reaching gauge internals.

Use of a diaphragm seal

A chemical diaphragm seal can be used to isolate the gauge internals from over temperature by physically blocking convection flow from the measured media to gauge internals.

Use of a high temperature lens and gasket

When ambient temperatures are above 200°F, the use of a high temperature lens (single pane tempered glass) and high temperature gasket should be used.   Additionally, a high temperature dial should be used (nonpainted-aluminum finish).

 

TABLE OF TEMPERATURE LIMITS

Gauge Internals/Filling	Maximum Ambient Temperature Fahrenheit	Maximum Process Temperature Fahrenheit	Minimum Fahrenheit
Standard Gauge
Brass Movement	200º (1)	150º	Unknown
Brass Movement Silver Brazed Internals (2)	200º (1)	250º	Unknown
316/316SS Movement	200º (1)	392º	Unknown
(1) When ambient temperatures are above 200°F, the use of a high temperature lens (single pane tempered glass) and high temperature gasket should be used (see above). (2) We use soft solder on brass internals in pressure ranges below 800 PSI and silver braze all internals above this as standard (Optional silver brazing below 800 PSI available). (3) Gauges with  316 Stainless Steel internals are argon arc welded and the above temperature limits would not apply. (High process temps exceeding 800º F -use of a pigtail reccomended)
Oil Filled Gauge
Glycerin	Neoprene Seals in the gauge determines Maximum Degree Fahrenheit.  Estimate 200ºF dependent upon conditions.		0
Glycerin/10% Water	Same as above		-10
Glycerin/20% Water	Same as above		-20
Glycerin/30% Water	Same as above		-30
Glycerin/35% Water	Same as above		-40
Silicone	Same as above		-60
Ethylene Glycol	Same as above