| Selecting a Pressure Gauge |
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When Selecting a pressure gauge, it is important to consider the following
factors to insure safety and accuracy:
- Pressure fluid composition
- Pressure fluid temperature
- Ambient conditions
- Pressure Range
- Conditions affecting wear of the system
- Method of mounting
- Required accurac
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Pressure fluid composition
Since the sensing element of a pressure gauge may be exposed directly
to the measured medium, consider the characteristics of this medium. It
may be corrosive, it may solidify at various temperatures, or it may contain
solids that will leave deposits inside the sensing element. For pressure
fluids that will not solidify under normal conditions or leave deposits,
a Bourbon tibe gauge is acceptable. Otherwise a Sealgauge or chemical
seal should be used. A chemical compatibility chart follows this section
to aid in the selection of the proper sensing element material.
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Pressure fluid temperature
Steam and other hot media may raise the temperature of the gauge components
above safe working limits of the sealed joints. In these cases it is recommended
that a siphon, cooling tower or chemical seal be used in conjunction with
the pressure gauge.
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Ambient Conditions
The normal ambient temperature range for WIKA pressure gauges is -40 degrees
Fahrenheit to +140degrees Fahrenheit (-20 degrees Celcius to +60 degrees
Celcius) for glycerine-filled gauges. The error caused by temperature
changes is +0.3% or -0.3% per 18 degrees Fahrenheit rise or fall, respectively.
The reference temperature is 70 degrees Fahrenheit (20 degrees Celcius).
The correction is for the temperature of the gauge, and not the temperature
of the measured medium. Remote gauge mounting using a chemical and capillary
line is one alternative for applications involving extreme ambient temperature.
Moisture and weather effects must also be considered. Liquid filled gauges
prevent condensation build up. For outdoor use, stainless steel, brass,
or plastic cased gauges are recommended.
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Pressure range
A gauge range of twice the working pressure is generally selected. The
working pressure in all cases should be limited to 75% of the gauge range.
Where alternating the pressure and pulsation are encountered, working
pressure should be limited to 2/3 of the gauges range.
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Conditions affecting wear of the
system.
In applications involving severe pressure fluctuation or pulsation, the
use of restrictors and/or snubbers is recommended. In addition, liquid-filled
gauges increase the service life of gauges in these conditions. WIKA liquid-filled
gauges are generally filled with glycerine. Silicone for larger temperature
extremes and Halocarbon for use with oxidizing agents such as chlorine,
oxygen, and hydrogen peroxide are also available. |
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Method of mounting
Radial (LM) and back (CBM or LBM) connections are available for most WIKA
gauges. WIKA stocks gauges with standard NPT threaded connections. Other
types such as metric threads, straight threads, hose barbs, and special
fittings are available as a special order.
Pressure gauges should be mounted in the upright position. For applications
where the gauge is mounted sideways, horizontally, or upside down, contact
us at info@buywika.com
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Required accuracy
WIKA stock gauges with accuracies from +/- 3/2/3% to +/- 0.1% span (ASME
Grade B to Grade 4A). Generally, the more accurate gauges are larger and
more costly. |
