SP970A, B, C AND D MANUAL AND MINIMUM POSITION PRESSURE REGULATORS
Table 1. Port Identification.
SP970A Pressure
Regulator
SP970A Minimum Position SP970B SP970C, D
SP92
SP93
Main
1
1
1
1
2
M
Pilot
√
4
√
3
4
P
Branch
2
2
2
2
3
B
Exhaust
4
√
4
4
√
√
Calibration
All SP970A and C models are calibrated at 8 psi (55 kPa)
when the calibration mark (center punch) on the shaft is
centered at the bottom of the molded V. To calibrate,
align the center punch mark on the shaft with the bottom
of the molded V groove on the plastic surrounding shaft.
See Fig. 3. This setting equals 8 psi (55 kPa). Secure the
knob to the shaft at the proper scale setting. The knob
should be pointing to 8 psi (55 kPa). See Fig. 4.
All SP970B and D models are calibrated at 8 psi (55 kPa)
when the knob is set at 50 percent.
The large range device can be field recalibrated to other
end points with the same span from 0 psi (0 kPa) lower
limit to 26 psi (179 kPa) upper limit. The small range
device can be field recalibrated to other end points with
the same span from 0 psi (0 kPa) lower limit to 16 psi
(110 kPa) upper limit.
Checkout and Test for All Models
1.
With main air connected, insert a pressure gage
into the branch line.
2.
Check pressures equivalent to knob settings.
3.
When minimum position is used, attach input and
increase pilot pressure.
4.
Verify correct operation.
ENGINEERING DATA
Specifications
Models:
- SP970A: A bleed type pressure regulator.
- SP970B: A bleed type pressure regulator mounted
on a sheet metal panel.
- SP970C: A bleed type pressure regulator with a
dead ended pilot chamber for minimum pressure
applications.
- SP970D: A bleed type pressure regulator with a
dead ended pilot chamber for minimum pressure
applications mounted on a sheet metal panel.
Selectable Spans for psi (kPa):
See Table 2.
Table 2. Selectable Spans.
Model
Knob Rotation
a
188
244
300
Small span
5 (34)
6.5 (45)
8 (55)
Large span
10 (69)
13 (90)
16 (110)
a
The setpoint knob normally rotates 188 degrees. Two
breakaway stops on the knob allow rotation of 244 and
300 degrees.
Operating Pressure (Switch and Pilot) Range:
Normal Main: 18 psi (124 kPa)
Branch: 3 to 15 psi (21 to 103 kPa)
Pilot: 3 to 15 psi (21 to 103 kPa)
Maximum Safe Air Pressure:
30 psi (207 kPa)
Ambient Operating Limits:
Temperature: 0 to 140°F (-18 to 60°C)
Relative Humidity : 5 to 95%
Air Handling Capacity:
SP970A, B: above minimum position, device feeding
pilot determines capacity. Below minimum position,
air capacity is 0.022 scfm (10 ml/s)
SP970C, D: 0.022 scfm (10 ml/s)
Air Consumption:
0.022 scfm (10 ml/s)
Scaleplate:
All models ship with a 0 to 100 scaleplate
(including knob and locknuts).
Construction:
Molded plastic with neoprene diaphragm,
steel spring and shaft.
Operation
SP970A and B: Three Port Switches
PRESSURE REGULATOR OPERATION
Main line air flows through the restriction into the
branchline chamber and out the nozzle. Branchline
pressure increases until it is strong enough to compress
the spring and lift the diaphragm off the nozzle. Airflow
out the nozzle is controlled by the balance between the
branchline pressure and spring force.
MINIMUM POSITION OPERATION
An external signal is connected to port 4 (exhaust port).
When the external signal is greater than the spring load,
the nozzle opens and branchline pressure is the same as
the external signal. When the external signal is less than
the spring load, branchline pressure is controlled as
described in the previous paragraph. See Fig. 6.
SP970A,B
4
SP970A,B
2
2
BRANCH
BRANCH
1
PILOT
MAIN
PILOT
MAIN
4
C4298
Fig. 6. SP970A/B operation.
3
95-7237EF
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