Cashco 764T User Manual
INSTALLATION, OPERATION, & MAINTENANCE MANUAL
IOM-764T
12/13
MODEL 764T
PNEUMATIC TEMPERATURE CONTROLLERS
SECTION I
I. DESCRIPTION AND SCOPE
The Model 764T is a temperature controller with an integral, rigid insertion bulb used for sensing temperature, and
outputting a pneu mat ic signal proportional to the deviation from the setpoint.
This IOM-764T does not cover use of oxygen as the "instrument air" fl uid. Such an application is outside the scope
of this IOM.
With proper materials and pipe sizes, the 764T can be used to measure the tem per a ture of liquid, gaseous, or va por
service. The installation of the thermal bulb can be direct or in di rect using a thermal well. Refer to Technical Bulletin
764T-TB for de sign and selection rec om men da tions.
Abbreviations Utilized:
IAS - Instrument Air Supply ES - Electrical Supply CW - Clockwise
SIG - Signal TC - Temperature Control valve CCW - Counter Clockwise
P/P - Pneumatic-to-Pneumatic P1 - Inlet Pressure REV - Revolution or Reverse
TC - Temperature Controller P2 - Outlet Pressure DIR - Direct
TI - Temperature Indicator TR - Condensate Trap FS - Flow Switch
SRV - Safety Relief Valve PB - Proportional band SOV - Solenoid Valve
II. INSTALLATION
1.
a.
b.
c.
d.
e.
Location of the thermal bulb into the medium
being con trolled is crit i cal.
Always insert the maximum bulb length into
the medium.
Always locate the bulb at a point downstream
of a heat exchanger to assure a near-equal
dis tri bu tion of the tem per a ture across the containment cross-section.
Always locate the control valve doing the tem per a ture control no further than 6-10 feet (2-3
meters) away from the controller when the
control valve does not have a po si tion er.
Do not use a thermal well unless the Owner's
process conditions, safety considerations or
main te nance pro ce dures require such; a ther mal
well enters an extra time response delay (i.e.
reduction in sensitivity) to the closed loop.
If a thermal well is required,to maximize heat
transfer effi ciency, locate on the top of a pipe
(vertical or at a 45° angle), duct, or at a 45°
SECTION II
f.
Figure 1: Typical Direct Cooling Application
angle to a vertical wall or horizontal top, when
possible, to allow fi lling of "void space" in well
with a suitable liquid heat transfer medium.
(See Figure's 4 and 5).
If a thermal well must be installed in a hor i zon tal
ori en ta tion, attempt to "pack" the "void space"
with steel or SST wool at bulb in ser tion. Use of
the well packing will in crease thermal effi ciency
(re duce time con stants) above that of a "dead
air" space in the "void space"; i.e. dead air space
acts as an "in su la tor" to heat transfer.
g.
Indoors, controllers without a thermal well
may be oriented in any position.
6.
Use suitable pipe thread sealant when in stall ing a
ther mal well or a 764T thermal bulb.
h.
i
j.
2.
The name plate of a 764T only indicates the
rotation to change temperature setpoint. It is rec om mend ed that a thermometer be in stalled very
near the location of the 764T. If the 764T utilizes
a thermal well, then the ther mom e ter should also
use a thermal well. If the 764T does not use a
thermal well, then the ther mom e ter should not
use a thermal well.
Outdoors, controllers without a thermal well
should be mounted with the main longitudinal
axis horizontal or be low. Make sure that the
vent port (either A or B) will not take in rain wa ter; use an angle fi tting, if necessary.
Indoors, controllers with a thermal well should
be mounted as recommended in Article 1.e.
Outdoors, controllers with a thermal well
should be mount ed at a 45° angle to main
pipe or duct axis, when possible. Make sure
that the vent port (either A or B) will not take
in rainwater; use an angle fi tting if necessary.
The con trol ler can be installed at any angle
below 45° at reduced ther mal sensitivity.
CAUTION: When engaging the threaded bulb con nec tion into its coupling or thermal well, DO NO
GRASP THE PNEUMATIC HOUSING OR KNURLED
LOCK NUT AND MANUALLY RO TATE THE CON TROL LER; ONLY USE A WRENCH (1-3/8") AND
TIGHT EN AT THE HEX SUR FACE PRO VID ED!
! Failure to comply may cause the factory-set cali-
bration to be al tered, re quir ing shop re-calibration.
Ro tate the unit CW (viewed from housing end) to
engage threads.
7.
Clean the pip ing and tub ing of all for eign ma te ri als
in clud ing chips, burrs, dirt, etc. prior to use. Use care
in ap ply ing thread seal ant or TFE tape to pre vent
ex cess ma te ri al from en ter ing the fl ow path.
3.
Recommended pipe tap size is 1/2" NPT for a
thermal bulb without a thermal well.
4.
Recommended pipe tap size is 3/4" NPT for a
thermal bulb with a thermal well.
5.
If the pipe tap size is greater than the size required
by either the thermal bulb or thermal well, a pipe
bushing fi tting is recommended rather than bell
reducers to bring the tap size to that required.
Figure 2: Typical Indirect Heating Application
Figure 3: Alternating Heating?Cooling System with
Split-Range Pneumatic (P/P) Positioners "Fail" to Cooling Mode on Loss of Air Supply
8.
KEEP CANTILEVERED PIPE, AIRSET, OR OTH ER
AP PUR TE NANC ES TO A MIN I MUM. It is recommended that the airset supplying in stru ment air be
independently mount ed elsewhere and tubed to the
con trol ler. Failure to comply with this rec om men da tion
may result in the even tu al loosening of the housing
from the thermal bulb, causing the unit to go out of
calibration.
9.
Connect piping/tubing per Tables 1 and 2. Do not
plug or restrict the open (unused) port (A or B) vent
connection. Port "A", Port "B" and "OUT PUT" are
identifi ed on the housing cast ing.
10.
764T's can operate with a lubricated, non-dried air
supply; however, good practice and other system
components (airsets, po si tion ers, relays, etc.) re quire
the use of the highest quality air supply available; i.e.
non-lu bri cat ed compressed air source and desiccant
dried air.
2
IOM- 764T
TEMPERATURE
11.
Instrument air exposed to outdoor freezing tem per a tures must be desiccant dried. Re frig er at ed
drying is not ad e quate.
12.
Instrument air exposed to indoors and/or no-freezing
tem per a tures is recommended to be re frig er ant
dried as a minimum.
13.
If the air supply is at a remote location, and can
not be practically dried and bears oil (i.e. plant air),
co a lesc ing fi lters must be utilized to re move as
much oil and water as possible, as well as par ti cles
over 15 mi crons size.
TABLE 1
Controller Model 764T
ISA to
Port
A Exhaust Supply
B Supply Exhaust
PROCESS
Direct Reverse
Increase in
temperature
increases output
signal
Action
Increase in
temperature
decreases output
signal
TABLE 2
Controller "Heating Applications"
IAS to
Port
A
B
B
A
Control Valve Controller
ATO-FC
(Reverse)
ATC-FO
(Direct)
ATO-FC
(Reverse)
ATC-FO
(Direct)
Actions
Reverse
Increase in temperature
decreases output signal.
Valve "fails" to "cooler"
process temperature.
Direct
Increase in temperature
increases output signal.
Valve "fails" to "hotter"
process temperature.
"Cooling" Applications
Actions
Direct
Decrease in temperature
decreases output signal.
Valve "fails" to "hotter"
process temperature.
Reverse
Decrease in temperature
increases output signal.
Valve "fails" to "cooler"
process temperature.
IOM-764T
Figure 4: Recommended Thermal Well (Opt. 64) Installation
3
FOR IN SER TION
INTO PIPE PEPENDICULAR TO CENTERLINE OF PIPE,
PIPE SIZE MUST
BE 8" (DN 200) OR
LARG ER, WITH
OR WITH OUT A
THERMAL WELL.
Ø
1
Ø
2
Nipple Length
L
2
Inch (DN) Inch (DN) Inch (mm)
1/2" 15 1" 25 6" (152)
3/4" 20 1-1/4" 32 6" (152)
1" 25 1-1/4" 32 6" (152)
1-1/4" 32 1-1/2" 40 6" (152)
1-1/2" 40 2" 50 6" (152)
2" 50 2" 50 NR
2-1/2" 65 2-1/2" 65 NR
NR = Not Required
Figure 5: Recommended Thermal Well (Opt. 64) Installation
Figure 6: High Temperature Thermal Bulb (Opt. 63)
4
IOM- 764T
PRINCIPLE OF OPERATION
III.
SEC TION III
1.
2.
3.
The 764T controller employs laminar fl ow to
de vel op the 3-15 psig (nominal 0.2 - 1.0 Barg)
output sig nal. Lam i nar fl ow was chosen because
it eliminates the need for range springs, levers,
pivots and other parts that pro duce friction and
lost motion.
A bimetallic thermal bulb is used to measure
tem per a ture. It is immersed in the fl uid whose
tem per a ture is to be controlled. A temperature
variation changes the length of the outer tube
more than it changes the length of the Invar rod.
This difference produces a minut movement of
the end of the Invar rod that contacts the sensor
plate. The sensor plate, in turn, throttles the fl ow
of instrument air through the sensor to develop
the 3-15 psig (0.2 - 1.0 Barg) output signal.
On direct acting controllers, see Figure 7, the
supply enters PORT B. With an increase in the
4.
5.
6.
sensed tem per a ture the supply air fl owing through
the sensor orifi ce in creas es, which elevates the
output signal. The pro por tion al band restriction
regulators the fl ow of ex haust through PORT A.
On reverse acting controllers the supply enters
PORT A and passes through the proportional
band re stric tion. With an increase in the sensed
tem per a ture the fl ow through the sensor or i fi ce
is increased, which reduces the output signal.
PORT B is the exhaust port.
Closing the proportional band adjusting screw
reduces the proportional band. Opening the screw
increases the proportional band.
The setpoint adjustment moves the sensor closer
to, or further away from, the sensor plate to change
the controlled temperature. Rotate clockwise
to increase temperature set point and counterclockwise to decrease temperature set point.
IOM-764T
Figure 7: 764T Direct Action View Shows Port A & B
Rotated From Actual Position
5
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