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Chemical seals are used when the process medium is corrosive, viscous,
solidifying or contains solid particles. They might also be applied to
prevent entrance of hygiene or food products into the process to
safeguard bacteria growth.
This
section of our catalogue is designed to categorize all Indumart chemical
seals to explain the limitations for selecting the required seals which
suits your process. For a careful selection of the right chemical seal,
the following specifications must be stated:
| ●Material of Construction |
●Pressure Rating |
| ●Process Connection & Capillary
Length |
●Process and Ambient
Temperatures |
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Material
of Construction
Choosing the right
diaphragm seal whose materials of construction is chemically compatible
with the process fluid is very important. Selecting an unsuitable
diaphragm material may result in excessive wear and render the system
inaccurate or inoperable.
As a standard
practice, Indumart chemical seals are manufactured from 316L stainless
steel, but other materials such as 321 stainless steel, Monel,
Hastelloy, Tantalum and Nickel can be ordered for special processes.
Several types of lining such as, PVC, PTFE or Polypropylene may also be
applied to the system for protection. Gold-coating of 40 micron is also
a very good choice for withstanding extremely corrosive acids.
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Process Connection and Capillary
Length
The process side of
Indumart diaphragm seals are offered with either flanged or threaded
connection. The other end of the diaphragm seal may be attached directly
through the threaded connection, or remotely by the means of a filled
capillary, to the pressure instrument.
Diaphragm size of the
pressure seals varies according to the minimum and maximum pressure
values of the process. Large diaphragms are more sensitive to the
pressure input, resulting in more accurate systems. They contribute less
to the system spring rate and are less sensitive to ambient and process
temperature changes.
Capillaries used have
an internal diameter of 2 mm through which the fill fluid transmits the
pressure of the process to the measuring instrument. An inside diameter
of 1 mm is also possible to reduce the temperature effect, but it
negatively influences the response time. For reliable measurement
performance a limit to the length of capillary is set for each chemical
seal application.
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Pressure Rating
The process side of
Indumart diaphragm seals come with either flanged or threaded
connection. The instrument end of the seal may be attached directly or
remotely, by means of a filled capillary, to the pressure instrument.
The minimum and maximum process pressure values are important
determinants of the diaphragm size and process connection. The minimum
span specified is the minimum pressure which results in reliable
measurement performance. In most cases, a lower pressure than mentioned
is possible, but it reduces the accuracy of the measurement.
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Process and Ambient Temperatures
The specific
characteristics of any material will change when its temperature is
altered. In the diaphragm seal cases, characteristics of both the
diaphragm and the filled liquid are affected by changes in temperature,
which will result in temperature induced errors. This is the primary
cause of inaccurate pressure measurements occurring at a temperature
other than the calibration temperature of 20°C.
Expansion or
contraction of the fill fluid directly affects the pressure measurement.
Therefore, temperature changes should be noted at the time of ordering
for selection of correct fill fluid, as well as, safeguarding or
reducing temperature induced errors by using proper accessories.
Effects of
temperature on the accuracy of pressure measurements with 2" flange size
diaphragm seals are shown in the following tables. Calibration
temperature is 20°C.
Pressure error in kPa per 10°C temperature for 2" flange diaphragm seal
system at 10°C calibration temperature.
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Indumart
Standard Diaphragm Seals - Quick Selection |
|
Model: S11
● Stainless steel body
and diaphragm; Other materials & coating as option
● 1/4", 1/2", 3/4" and
1" threaded process connection, Other threads as option
● 1/4" and 1/2"
threaded instrument connection; Welded or capillary as
option
● Min. pressure span
of various models: from 15 psi to 1,500 psi
● Max. pressure of
various models: from 900 psi to 6,000 psi
● Max. temperature
200°C with PTFE ring; 345°C with graphite ring as option |
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Model: S21
● Stainless steel body
and diaphragm; Other materials & coating as option
● 1/4", 1/2", 3/4" and
1" threaded or 1/2" up to 1-1/2" flange process connection
● 1/4" and 1/2"
threaded instrument connection; Welded or capillary as option
● Min. pressure span
for pressure gauges from 7.5 psi
● Min. pressure span
for gauge pressure transmitters from 1.1 psi
● Min. pressure span
for differential pressure transmitters from 0.15 psi
● Max. pressure of
various models from 1,500 psi to 4,500 psi
● Max. temperature
200°C with PTFE ring; 345°C with graphite ring as option |
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Model: S31
● Stainless steel body
and diaphragm; Other materials & coating as option
● Process connection
hygienic type; 3A connection clamp or female connection
● 1-1/2", 2" & 3"
female coupling or 3/4", 1-1/2", 2" & 3" tri clover clamp (3A)
process
connection
● 1/4" and 1/2"
threaded instrument connection: capillary tube as option
● Min. pressure span
for pressure gauges from 7.5 psi (0.5 bar)
● Min. pressure span
for gauge pressure transmitter from 3 psi (0.2 bar)
● Min. pressure span
for differential pressure transmitters from 0.3 psi (0.02 bar)
● Max. pressure of
various models from 150 psi (10 bar) to 600 psi (40 bar)
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