4 | Baker Hughes
© 2021 Baker Hughes Company. All rights reserved.
Description
The
Masoneilan
37/38
spring-diaphragm
actuator is a simple, powerful, mechanical
device. There are two general types:
Air-to-
Extend
Stem
and
Air-to-Retract
Stem
.
Actuators are designated by case size: Nos. 9,
11, 13, 15, 18 and 18L.
The nominal range of a spring-diaphragm
actuator is the air pressure range in pounds per
square inch (psi) for rated stroke under no load.
Common ranges are 3
–15 psi and 6–30 psi.
The spring range and maximum allowable
supply pressure are marked on the serial plate.
For a 3
–15 psi nominal range, the stem will
start to stroke when the air pressure reaches 3
psi, and will complete the stroke when the
pressure reaches 15 psi (plus or minus 5%).
In the air-to-extend actuator, conformation of
the molded diaphragm to the diaphragm plate
serves as a flexible upper guide for the actuator
stem (26). The lower guide is an oil-
impregnated bronze bushing (37) located in the
spring adjustor (36). The air-to-retract actuator
differs from the air-to-extend unit in that the
spring (22), spring barrel (71) and spring
adjustor (36) are located
above
the diaphragm
plate (40) and diaphragm (39) which are
inverted. A gasket (19) at the joint of the
diaphragm case and yoke and a packing box
around the actuator stem prevents air leakage.
The diaphragm acts as a flexible upper guide
and the packing box assembly as the lower
guide for the actuator stem.
Air connections are 1/4" NPT. Connections are
located in the upper diaphragm case (air-to-
extend
actuators)
or
yoke
(air-to-retract
actuators).
Standard
Actuator
Size
Effective
Diaphragm
Area (sq.
in.)
Maximum
Stroke (in.)
9
45
¾
11
71
1
13
105
1 ½
15
145
2
18
200
2 ½
18L
200
4
Maintenance
Air-to-Extend Actuators (Type 37)
Diaphragm Replacement
Before disassembling the actuator, all spring
compression should be relieved by turning the
spring adjustor (36), to prevent the upper case
popping up when the cap screws (45) are
removed. This is especially important on actuators
with a high initial spring setting. Remove cap
screws (45), nuts (46) and upper diaphragm case
(43). Remove nut (30) and washer (41) to release
the diaphragm (39). If possible, the replacement
diaphragm should be of the molded type supplied
by GE Masoneilan, but in an emergency a
diaphragm may be cut from flat sheet stock for up
to and including No. 15 actuators. To allow
sufficient stroke without restriction due to flatness
of the diaphragm, the diaphragm bolt circle should
be about 10% greater than that of the diaphragm
case.
Replace washer (41), nut (30) and upper
diaphragm case.
Spring Adjustment
An air supply, with a gauge and regulator, should
be piped to the upper diaphragm case for this
adjustment. Adjust spring compression so that the
actuator stem (26) just begins to move when air
pressure reaches minimum pressure of the range
stamped on the serial plate. This movement is
most easily detected by feeling the stem as air
pressure is applied.
Note: Adjust spring compression only when
there is no air pressure on diaphragm.
