EH-0122 Tobar Electronic Absolute Pressure Transmitters
                          ENVIRONMENT, SAFETY & HEALTH

                                 SAFETY ACTION

Assistant Secretary for                              U.S. Department of Energy
Environment, Safety & Health                         Washington, D.C.  20585

DOE/EH-0122                     Issue No. 90-1                    January 1990

Tobar Electronic Absolute Pressure Transmitters

Product:

Tobar Model No. 75PA11110/33013.D3 Absolute Transmitter

Problem:

Four Tobar electronic absolute pressure transmitters exhibited severe zero
drift at elevated temperatures at a DOE contractor facility.  The four
transmitters were returned to the manufacturer.  An extensive investigation of
the returned transmitters concluded that the zero shift resulted from loss of
vacuum of the primary unit with three of the transmitters.  The fourth unit
showed stability shift when operating under high temperature and turndown
conditions.  A minute crack was found in the glass seal for the wire leads
from the primary which allowed small inleakage to the evacuated reference
chamber for one of the absolute pressure transmitters.  The primary units were
replaced in the four transmitters, which were then subjected to an accelerated
aging process at elevated temperatures.  The four transmitters were then
returned to the contractor.

The manufacturer encourages the return of any questionable transmitters in the
noted series to them for testing.  They are now performing a 96-hour test on
all absolute transmitters and no longer manufacture the above style header.

Action:

Evaluate all Tobar transmitters of the above series procured between September
1988 and September 1989 for the zero drift problem at elevated operating
temperatures.  Stability is only an issue at high operating temperatures and
is NOT easily detectable at specified reference conditions of URL and 25
degrees C ambient temperatures for short periods of time.

If any problems are found, the transmitters should be returned to the
manufacturer: Camille Bauer, Inc., 7425 South Harl Avenue, Tempe, AZ 85283,
Phone:  602-345-6300.



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This publication is one of several series of bulletins published so that DOE
program managers and contractors can share information about potential
occupational safety problems relevant to DOE operations.  For more information
or additional copies, contact Eleanor Crampton, Performance Evaluation
Division, Office of Safety Compliance, Assistant Secretary for Environment,
Safety & Health, U.S. Department of Energy, Washington, DC 20545; Telephone
FTS 233-3732, Commercial (301) 353-3732.
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