Data Sheet

Bulletin 71.4:MR108
3
Introduction
The Type MR108 regulators are direct-operated,
backpressure, high-capacity, multi-purpose regulators.
They are designed to handle pressures up to 400 psig /
27.6 bar and temperatures up to 250°F / 121°C.
This product provides a fast, simple, reliable and
economical backpressure control in multi-purpose
applications suitable for different ow media including
liquid, air and gas. Applications include lube oil systems
and any application where speed of response is critical,
minimum differential pressure is a concern or uid
is not free of impurities. Type MR108 backpressure
regulators with low-pressure actuators can be set up to
35 psig / 2.4 bar and the high-pressure actuator version
can be set to 150 psig / 10.3 bar for constructions with
Fluorocarbon (FKM) diaphragm and 300 psig / 20.7 bar
for constructions with Nitrile (NBR) diaphragm.
The units are available in 4 sizes, NPS 1 through 4 /
DN 25 through 100 and are available in several
end connection congurations to meet demands on
application requirements.
Available with a quick-opening cage for quick speed
of response and high ow capacity. The cage-guided
metal plug provides superior control and stability.
The Type MR108 with Steel or Stainless steel body
construction has been designed to meet API 614 as
required by lube oil manufacturers.
Features
LargeFlow—Able to pass large ow rates with a
minimum pressure buildup.
Stability—The Type MR108 regulator’s cage-guided
metal plug design provides superior control stability of
delivery pressure.
FastResponse—Direct-operated for fast
response to meet the most demanding pressure and
ow requirements.
EasyDrain—Feature allows you to drain the
system without expensive spool pieces saving you
time and space.
EasyBleed—Feature allows you to purge the air
trapped underneath the diaphragm when the high-
pressure regulator is installed in the upright position,
which improves speed of response.
SteelandStainlessSteelConstructionsMeet
API614Requirements—Steel and Stainless steel
body constructions comply with the recommendations of
API Standard 614.
AvailableConstructionstoMeetNACEMR0175-
2003andNACEMR0103Requirements
forSourGasServiceCapability—Optional
materials are available for applications handling
sour gases. These constructions comply with the
recommendations of NACE International Standards
MR0175 and MR0103.
MultipleTrimMaterialsAvailable—416, 316 and
316L Stainless steel options are available to meet
wider application requirements including demands
from lube oil and cooling water applications.
ANSI/FCI70-3-2004ClassVIShutoff—Soft-seat
valve plug seals for tight shutoff.
MultipleEndConnectionOptions—Type MR108 is
available in several end connection congurations to
meet demands on application requirements.
P
1
= P
2
onHigh-PressureActuator—Inlet pressure
rating equals outlet pressure rating on high-pressure
actuator constructions up to 400 psig / 27.6 bar.
PrincipleofOperation
Refer to Figure 2. The Type MR108 is a multi-
purpose backpressure regulator. Upstream 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 uid 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 the
valve spring forces push the actuator stem downward,
the valve plug moves closer to the seat ring and the
ow decreases downstream as the regulator closes
in response to the decreased pressure underneath
the diaphragm.