Type MR108
3
Introduction
Scope of the Manual
This instruction manual provides installation,
adjustment, maintenance and parts ordering
information for Type MR108 backpressure regulators.
Description
The Type MR108 regulators are direct-operated,
backpressure, high-capacity, multi-purpose regulators.
They are designed to handle pressures of up to
400 psig / 27.6 bar and temperatures of up to 250°F /
121°C. Large multi-purpose regulators provide fast,
simple, reliable and economical pressure control for
a number of applications and are suitable for different
flow media such as liquid, air and gas. In addition,
the drain valve option allows you to drain the system
without expensive spool pieces saving you time and
space. Also, the bleed valve option allows you to
purge the air trapped underneath the diaphragm when
the high-pressure regulator is installed in the upright
position. Typical applications include lube oil, cooling
water and natural gas district stations. Type MR108
backpressure regulators are typically used in lube
oil installations or any application where speed of
response is critical, minimum differential pressure is a
concern or fluid is not free of impurities.
Principle of Operation
Refer to Figure 2. The Type MR108 is a multi-purpose
backpressure regulator. Inlet pressure is registered
externally through a 1/2 NPT control line connection
located at the low-pressure actuator bonnet or high-
pressure actuator lower casing. When inlet pressure
rises above the set pressure, the pressure under the
actuator diaphragm increases and opens the regulator.
This pressure overcomes the regulator setting (which
is set by the regulator control spring). Through the
action of the actuator stem, the valve plug is pulled
upward moving away from the seat ring and allowing
fluid to escape through the cage into the downstream
system. When inlet pressure drops back to set
pressure, pressure under the actuator diaphragm
decreases. The control spring and valve spring forces
push the actuator stem downward, the valve plug
moves closer to the seat ring and the flow decreases
downstream as the regulator closes in response to the
decreased pressure underneath the diaphragm.
Table 2.
Backpressure Control Ranges
ACTUATOR
TyPE
SPRINg RANgE
SPRINg
PART NUMBER
SPRINg
COLOR
CODE
SPRINg WIRE
DIAMETER
SPRINg FREE
LENgTH
MAxIMUM PRESSURE
OVER SETPOINT TO
AVOID INTERNAL
PARTS DAMAgE
psig
bar
In.
mm
In.
mm
psig
bar
Low Pressure
5 to 14
0.34 to 0.97
GE42909X012
White
0.44
11.2
9.70
246
20
1.4
8 to 24
0.55 to 1.7
GE42910X012
Silver
0.50
12.7
12 to 30
0.83 to 2.1
GE42911X012
Orange
0.56
14.2
15 to 35
1.0 to 2.4
GE43002X012
Red
0.63
16.0
High Pressure
25 to 40
1.7 to 2.8
GE42906X012
Blue
0.33
8.38
120
8.3
35 to 70
2.4 to 4.8
GE42907X012
Green
0.38
9.65
55 to 120
3.8 to 8.3
GE42909X012
White
0.44
11.2
90 to 200
(1)
6.2 to 13.8
(1)
GE42910X012
Silver
0.50
12.7
175 to 300
(2)
12.1 to 20.7
(2)
GE43002X012
Red
0.63
16.0
1. Maximum setpoint is limited to 150 psig / 10.3 bar for constructions with Fluorocarbon (FKM) diaphragm.
2. Not applicable for constructions with Fluorocarbon (FKM) diaphragm.
Table 3.
Wide-Open Flow and IEC Sizing Coefficients
BODy SIZE
WIDE OPEN COEFFICIENT
IEC SIZINg COEFFICIENT
Line Size Equals Body Size
C
1
K
m
F
L
x
T
F
d
NPS
DN
C
g
C
v
Quick Opening Cage
1
25
597
17.5
34.1
0.81
0.90
0.73
0.43
2
50
1740
48.2
36.1
0.81
0.90
0.82
0.34
3
80
3540
103.1
34.4
0.76
0.87
0.75
0.32
4
100
4300
135.9
31.6
0.72
0.85
0.65
0.3
Reduced Port Quick Opening Cage
2
50
1570
43.8
35.9
0.81
0.90
0.72
0.36
Linear Cage
1
25
463
13.7
34.0
0.81
0.90
0.73
0.36
2
50
761
22.5
33.8
0.75
0.87
0.72
0.24
