4 | Baker Hughes
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Product Description
The Model 78 Series pressure regulators are compact, lightweight,
high-performance pressure reducing instruments. They are used
primarily for supplying a stable source of air to process control
equipment such as current to pneumatic transducers and control
valve positioners.
Numbering System
Model No.
Pressure Range
Description
78-4
5-40 psi (35-280
kPa), (0.35-2.8 bar)
Air Loading with
Relief and Filter
78-40
5-100 psi (35-700
kPa), (0.35-7 bar)
Air Loading with
Relief and Filter
Specifications
Inlet Pressure Rating
210 psi (1.5 MPa, 15 bar) maximum
Pressure Set Range
5-40 psi (35-280 kPa, 0.35-2.8
bar)5-100 psi (35-700 kPa, 0.35-7
bar)
Connection
1/4 NPT
Rated Cv
0.25
Filter Element
Sintered Porous Polyethylene (5μ)
Ambient Temperature
Range
-40° to +83°C (-40° to +182°F)
Air Consumption
0.004 scfm (100 sccm)
Weight
14 oz. (0.4 kg)
Materials of
Construction
See Table next page
CAUTION
CAUTION
WARNING
DANGER
Do not install this Regulator in air lines which exceed
210 psi (1.5 MPa, 15 bar) pressure.
Installation
Clean the lines thoroughly to remove all dirt, scale or other
foreign matter before installing the regulator. Install with flow
in direction of flow arrows on regulator body. The airset should
be installed with the drain cock facing down. Regulator should
be installed as close as possible to device utilizing the reduced
pressure to minimize pressure drop. Do not use piping or tubing
smaller than the regulator connections since this will restrict flow
and reduce capacity.
It is recommended that pressure gauges be installed on the
inlet and outlet sides of the regulator as an aid in adjusting the
pressure and in monitoring of working pressures.
Operation
Prior to applying supply pressure, loosen knob lock screw
and turn pressure set knob counterclockwise. Turn on supply
pressure. Output pressure should be zero. Slowly rotate set knob
clockwise until desired pressure is reached. Tighten knob locking
screw to ensure that pressure remains set at desired value. When
changing output from a higher to lower pres¬sure, initially go to
lower than desired pressure, then increase to desired pressure.
Re-tighten knob lock-screw.
Maintenance
It is recommended that the drain cock be opened at regular
intervals to drain any fluid that may have collected in the dripwell.
The interval between draining will have to be determined based
on the actual rate of accumulation of fluid.
It is recommended that pressure gauges be installed on the
inlet and outlet sides of the regulator as an aid in adjusting the
pressure and in monitoring of working pressures.
CAUTION
CAUTION
WARNING
DANGER
The relief valve feature should not be confused with
any auxiliary safety valve which might be needed for
complete protection of air operated equipment. It is
intended only to provide more uniform controlled
pressure and to permit adjusting the outlet pressure
downward without venting the line.
CAUTION
CAUTION
WARNING
DANGER
Prior to performing maintenance on the regulator,
shut off the inlet and outlet pressures and remove the
spring compression by turning the setting knob fully
counterclockwise. Open the drain cock carefully to
relieve any retained pressure and drain the dripwell. It
is recommended that the regulator be removed from
the line for repairs.
CAUTION
CAUTION
WARNING
DANGER
When draining the dripwell, open the drain cock slow-
ly and collect the fluid in a suitable container for safe
disposal.
NOTE:
• Considering the high labor costs involved in replacing
internal parts, it may be more economical to stock
complete units.
• Care must be taken to avoid damage to the plug and
stem assembly.