6
TEMPERATURE SWITCHES
THERMOWELLS
Thermowells must be used on any
application where the bulb of the tem-
perature switch may be exposed to
pressure, corrosive fluids or high
velocity. Additionally, the use of a ther-
mowell permits instrument interchange
or calibration check without disturbing
or closing down the process.
Ashcroft temperature switches have
bulb diameters to match
3
⁄8˝ nominal
bore thermowells Is. The bulbs have a
sensitive portion length of 2˝ which can
be used with 2
1
⁄2˝ “U” dimensioned ther-
mowells or longer. For maximum accu-
racy a thermowells “U” dimension
should be selected to permit complete
immersion of the sensitive portion plus
1˝ when measuring the temperature of
liquids; an extra 3˝ should be allowed
when measuring the temperature
of gases.
Thermowell bushings should be used
with remote mount temperature switches.
We recommend the standard 3˝ bulb
and code 69 Series bushings for use
with any thermowell “U” dimension. A
split rubber grommet allows easy instal-
lation and “S” dimension adjustment.
To order a thermowell, refer to Price
Sheet TH/PS-1 for complete information.
B-Series temperature switches feature
a SAMA Class II vapor pressure ther-
mal system. This system provides
quick, accurate response to process
temperature changes with negligible
ambient temperature effects. This is
inherent in the design due to the pre-
cise relationship that exists between
temperature and pressure according to
the vapor pressure laws. A wide selec-
tion of sensing bulb and armored capil-
lary lengths is available. The vapor
pressure system design features small
bulb sizes, making installation easy and
cost-effective.
All models feature ±1.0% percent of
span setpoint repeatability with very
high overtemperature ratings.
These standard designs perform well in
applications where shock and vibration
could be a problem and should be used
with Ashcroft thermowells for bulb pro-
tection and ease of installation and
maintenance.
STANDARD TEMPERATURE RANGE SELECTION
NOTES:
1 All deadbands given in °F.
2Available with remote mount thermal
systems only.
3Not available with 2
3
⁄4˝ stem.
4 Dual switch element multiply single switch
element value by 1.6 for approximate
deadband.
5 Set and reset points must fall within the
adjustable range.
INSTRUMENT (SWITCH)
CONNECTION
Maximum
Nominal Range
(1)
Temperature
Approximate Deadband
(1)
Switch Element
°F °C °F 20, 26, 27 21, 24, 31 50 22 32
–40 to 60 –40 to 160 400 1.0-2.0 3.0-8.0 1.5-5.5 1.4-6.0 8.0-16.0
0 to 100 –20 to 400 400 1.5-3.0 5.0-12.0 2.2-8.5 1.5-7.5 9.0-20.0
75 to 205 20 to 95 400 1.5-3.5 8.0-16.0 2.5-12.0 2.0-9.0 10.0-24.0
150 to 260 65 to 125 400 1.5-3.0 5.0-12.0 2.2-8.5 2.0-9.0 10.0-24.0
235 to 375 110 to 190 500 1.5-3.5 5.0-12.0 2.5-8.5 2.0-9.0 10.0-24.0
350 to 525
(3)
175 to 275 700 2.0-4.5 8.0-16.0 3.2-12.0 2.5-10.0 15.0-34.0
500 to 750
(2)
260 to 400 900 4.0-8.0 16.0-30.0 7.2-24.0 5.0-23.0 30.0-50.0
Bushing slides
along capillary
69 series
(XBX) bushing
Process
connection
1/2" NPT
“S”
“S”
3˝
U˝
(12 Seiten)
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