Data Sheet

Bulletin 71.4:MR98
3

pusher post assembly provides positive guiding for
improved shutoff.
  Small size allows easy installation
in limited spaces.
  Spring-loaded
PTFE packing and tapped connections permit
pressure loading of Types MR98LD, MR98HD and
MR98HHD spring cases.
  Handwheels (standard on the
Types MR98LD, MR98HD and MR98HHD and
optional on some sizes of the Types MR98L and
MR98H) allow easy pressure setting changes.
  Optional materials are
available for applications handling sour gases. These
constructions comply with the recommendations of
NACE International Standards MR0175-2002 and
MR0103. Optional materials are available to meet
ANSI/NACE MR0175/ISO 15156, please contact your
local Sales Ofce for special ordering instructions.
Customers have the responsibility to specify correct
materials. Environmental limitations may apply and
shall be determined by the user.
  —Steel and Stainless Steel
Constructions meet API 614 Requirements.
Hastelloy
®
C is a mark owned by Haynes International, Inc.
Monel
®
is a mark owned by Special Metals Corporation.
Introduction
MR98 Series (Figure 1) is used for backpressure or relief
applications in liquid, gas, air and steam service. The
Types MR98L, MR98H and MR98HH are direct-operated
and spring-loaded. The Types MR98LD, MR98HD and
MR98HHD use additional pressure loading to maintain
relief differential pressures, backpressures or for remote
setpoint adjustment.
Features
 Typical applications include control and
maintenance of backpressure on pumps, differential
pressure across lubricated seals, steam header
pressure, fuel and oil lines pressure, air supply
systems pressure, pump bypass applications for API
general and special purpose lube and seal oil systems,
relief applications for ash tanks and accumulators and
other process and industrial uses.
  Diaphragms come
in stainless steel, Monel
®
, Hastelloy
®
C or elastomers
and body is available in gray cast iron, steel, stainless
steel, Aluminum-bronze, Hastelloy
®
C and Monel
®
.
Corrosion-resistant trims are available.
  Diaphragm is isolated
from the main ow stream. Slotted valve plug and

BODY SIZE
X
T
F
D
F
L
K
m
In. DN
1/4 NPT - - - - 0.743 0.74 0.95 0.90
1/2 15 0.787 0.78 0.94 0.88
3/4 and 1 20 and 25 0.935 0.70 0.91 0.83
1-1/2 and 2 40 and 50 0.961 0.69 0.94 0.88
Flow Capacities
Types MR98L and MR98LD:
See Tables 7 through 11
Types MR98H and MR98HD:
See Tables 12 through 16
Types MR98HH and MR98HHD:
See Tables 17 through 21

Metal Seats: Class IV
Class IV
Elastomer Seats: Class VI or better
Pressure Registration
Internal or External
Approximate Weights
MR98H Series:
1/4 NPT body: 5 lbs / 2.3 kg
1/2 in. / DN 15 body: 10 lbs / 4.5 kg
3/4 and 1 in. / DN 20 and 25 bodies:
22 lbs / 10 kg
1-1/2 and 2 in. / DN 40 and 50 bodies:
55 lbs / 25 kg
MR98L Series:
1/4 NPT body: 7 lbs / 3.2 kg
1/2 in. / DN 15 body: 15 lbs / 6.8 kg
3/4 and 1 in. / DN 20 and 25 bodies:
35 lbs / 16 kg
Options
• Handwheel or tee handle for Types MR98L,
MR98H and MR98HH
• Tapped spring case vent for Types MR98L,
MR98H and MR98HH
• Seal washer to permit spring case pressure
loading for Types MR98L, MR98H and MR98HH