Engineering Data - Honeywell RP973A Notice D'utilisation

ENGINEERING DATA

Specifications
Model: RP973A Pneumatic Averaging Relay.
Operating Pressure Range:
Normal: 0 to 18 psi (0 to 124 kPa).
Maximum Safe: 30 psi (207 kPa).
Operating Air Pressure: 3 to 13 psi (21 to 90 kPa) input
and output.
Ambient Operating Limits:
Temperature: 0 to 140°F (-18 to 60°C).
Relative Humidity: 5 to 95%.
Air Consumption: .007 scfm max. (198 sccm).
Flow Capacity: .008 scfm (3.8 ml/s) at 18 psi (124 kPa)
through either input with the other input and output
(Port 2) at 0 psi (0 kPa).
Construction: Two filtered restrictions in a sonic welded
plastic housing.
Operation
The RP973A consists of two 0.005 in. (0.127 mm)
matched restrictors in a single housing. See Fig. 4.The
two signals to be averaged are each fed through a
restrictor to a common chamber. See Fig. 4A.
This construction ensures that the pressure at the output
can never be more than the average of the two input
pressures. This occurs often in valve-unit type averaging
relays. The higher pressure flows through the restrictor
and out the other input.
The output pressure is the average of the two input
pressures within ±20 percent or ±0.7 psi (4.8 kPa) of the
difference between the high and low. It always falls about
half way between the two input pressures. The closer the
input pressures are in psi (kPa), the more accurate the
RP973A becomes. If the inputs are 3 and 13 psi (21 and
90 kPa), the output is 8 ±2 psi (55 ±14 kPa). See Fig. 4. If
RP973A PNEUMATIC AVERAGING RELAY
the inputs are closer, 12 and 13 psi (83 and 90 kPa), the
output is closer to the average at 12.5 ±0.7 psi
(86 ±5 kPa).
3
INPUT 1
INPUT 2
5
3
INPUT 1
3 PSI (21 kPa)
INPUT 2
13 PSI (90 kPa)
5
Fig. 4. RP973A operation.
Application
The RP973A averaging relay is a bleed-type device that
requires its output line to be dead ended (0 scfm [0 ml/s]
air consumption). See Fig. 5.
CAUTION
Equipment Damage Hazard.
Add an isolation relay (RP470B lockout relay)
when an RP973 is feeding an air-consuming
device such as another RP973A averaging relay
or an SP970A,B pilot. See Fig. 5.
3
0.005 IN. (.127 MM)
RESTRICTOR
2
OUTPUT
0.005 IN. (.127 MM)
RESTRICTOR
A
2
OUTPUT
8 PSI (55 kPa)
B
C4299
95-7253EF