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Engineering Reference

High Temperature Applications


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 150 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 250F 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 200F, 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

200 (1)

150

Unknown

Brass Movement
Silver Brazed Internals (2)

200 (1)

250

Unknown

316/316SS Movement

200 (1)

Unknown (3)

Unknown

(1) When ambient temperatures are above 200F, 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 800 F -use of a pigtail reccomended)
Oil Filled Gauge      

Glycerin

Neoprene Seals in the gauge determines Maximum Degree Fahrenheit.  Estimate 200F 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

   

 


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McDaniel Controls, Inc.,  P.O. Box 187 Luling, LA 70070
Street address: 14148 Highway 90 West, Boutte, LA 70039 U.S.A.
Tel: 985-758-2782  New Orleans: 504-467-1333 Fax: 985-758-1688

E-mail: Click HERE to send mail Web address:  http://www.mcdanielcontrols.com