to inlet pressure bleeding through the Type 112
restrictor, provides a downward loading pressure to
keep the main valve diaphragm and plug assembly
tightly shutoff.
When the inlet pressure rises above the set pressure,
the pressure on the pilot diaphragm overcomes the
pilot control spring and opens the pilot valve plug. The
pilot then exhausts the loading pressure from the top
of the main valve diaphragm and plug assembly. The
inlet pressure unbalance overcomes the main spring
force and opens the diaphragm and plug assembly.
The pilot continuously exhausts process fluid when the
inlet pressure is above the set pressure.
As the inlet pressure drops below the set pressure,
the pilot control spring closes the pilot valve plug and
the exhaust to atmosphere stops. Force from the main
spring, along with pilot loading pressure, pushes the
diaphragm and plug assembly onto the tapered edge
seat, producing tight shutoff.
Backpressure Regulator
As long as inlet pressure remains below set pressure,
the Type MR98H pilot control spring keeps the
pilot valve plug closed. Force from the main spring,
in addition to inlet pressure bleeding through the
Type 112 restrictor, provides downward loading
pressure to keep the main valve diaphragm and plug
assembly tightly shutoff.
Table 1.
Type LR128 Main Valve Body Sizes, End Connection Styles, Structural Design Ratings and Maximum Operating Inlet Pressures
(1)
MAIN VALVE
BODY SIZE
MAIN VALVE
BODY
MATERIAL
END CONNECTION STYLE
(2)
STRUCTURAL
DESIGN RATING
(3)
MAXIMUM
OPERATING RELIEF
(INLET) PRESSURE
INCLUDING BUILD-
UP
(3)
MAXIMUM
OPERATING OUTLET
PRESSURE
In.
DN
psig
bar
psig
bar
psig
bar
1, 2,
3 and
4
25, 50,
80 and
100
WCC Steel
NPT or SWE (1 and 2 in. only)
1500
103
450
31.0
450
31.0
CL150 RF
290
20.0
290
20.0
290
20.0
CL300 RF
750
51.7
450
31.0
450
31.0
CL600 RF
1500
103
PN 16/25/40 RF
580
40.0
CF8M
Stainless steel
NPT (1 and 2 in. only)
1440
99.2
450
31.0
450
31.0
CL150 RF
275
19.0
275
19.0
275
19.0
CL300 RF
720
49.6
450
31.0
450
31.0
CL600 RF
1440
99.2
PN 16/25/40 RF
580
40.0
1. The pressure/temperature limits in this Instruction Manual and any applicable standard or code limitation should not be exceeded.
2. Ratings and end connections for other than ASME standard can usually be provided. Contact your local Sales Office for assistance.
3. Maximum cold working pressure (CWP) per ASME B16.34 or product bulletin limit, whichever is lowest. Temperature may decrease these maximum pressures.
Table 2.
Type MR98H Pilot Maximum Cold Working Pressure
(1)(2)
BODY SIZE
BODY AND SPRING
CASE MATERIAL
MAXIMUM INLET PRESSURE
MAXIMUM OUTLET PRESSURE
1/2 NPT
Steel
Stainless steel
450 psig / 31.0 bar
450 psig / 31.0 bar
1. The pressure/temperature limits in this Instruction Manual and any applicable standard or code limitation should not be exceeded.
2. Temperature and/or the body end connection may decrease these maximum pressures.
Table 3.
Relief Set Pressure or Backpressure Control Ranges
PILOT
SET PRESSURE RANGE
SPRING WIRE DIAMETER
SPRING FREE LENGTH
SPRING MATERIAL
SPRING PART NUMBER
AND COLOR
psig
bar
In.
mm
In.
mm
Type MR98H
35 to 75
70 to 140
130 to 200
100 to 375
150 to 375
(1)
2.4 to 5.2
4.8 to 9.7
9.0 to 13.8
6.9 to 25.9
10.3 to 25.9
(1)
0.234
0.283
0.331
0.375
0.394
5.94
7.19
8.41
9.53
10.0
2.595
2.44
2.250
2.60
5.063
65.9
62.0
57.2
66
129
Powder-coated steel
Powder-coated steel
Powder-coated steel
Powder-coated steel
Powder-coated steel
ERAA01910A0, Green
ERAA01911A0, Red
ERAA02889A0, Blue
ERCA04293A0, Unpainted
1N943427142, Unpainted
1. 150 to 375 psig / 10.3 to 25.9 bar spring range is only for the Type MR98HH pilot construction; consult the local Sales Office for this option.
4
Type LR128