C
O
M
P
INLET PRESSURE
OUTLET PRESSURE
ATMOSPHERIC PRESSURE
TANK PRESSURE
VACUUM PRESSURE
PRE-EXPANSION PRESSURE
INTERMEDIATE BLEED PRESSURE
PILOT SUPPLY PRESSURE
INTERMEDIATE PRESSURE
LOADING PRESSURE
PUMP PRESSURE
BYPASS PRESSURE
BACK PRESSURE
INLET PRESSURE
OUTLET PRESSURE
ATMOSPHERIC PRESSURE
VACUUM PRESSURE
PRE-EXPANSION PRESSURE
INTERMEDIATE BLEED PRESSURE
PILOT SUPPLY PRESSURE
INTERMEDIATE PRESSURE
PILOT SUPPLY PRESSURE
VACUUM PRESSURE
TANK PRESSURE
VAPOR PRESSURE
LOADING PRESSURE
BYPASS PRESSURE
BACK PRESSURE
PUMP PRESSURE
BOOST PRESSURE
EXHAUST
PILOT LOADING PRESSURE
VENT HEADER PRESSURE
INLET BLEED PRESSURE
RELIEF PRESSURE
RELIEF PRESSURE
BOOST PRESSURE
MONITOR MOVING PRESSURE
STABILIZED PRESSURE
INLET BLEED PRESSURE
INITIAL STEP-DOWN PRESSURE
OUTLET PRESSURE (WHEN LOADING PRESSURE IS EQUAL TO OR GREATER THAN SETPOINT)
!
TYPE MR98H
TYPE 63EG
FIXED RESTRICTION
CONTROL LINE
(MUST BE AT LEAST
3/8 IN. / 9.5
mm TUBING)
PILOT EXHAUST
(PIPE DOWNSTREAM
IF MINIMUM DIFFERENTIAL
IS MET)
A6926_2
INLET PRESSURE
OUTLET PRESSURE
LOADING PRESSURE
ATMOSPHERIC PRESSURE
Note: On an actual Type 63EG-98HM, the pilot spring case points downstream.
Principle of Operation
As long as inlet pressure remains below set pressure,
the pilot control spring keeps the pilot valve plug
closed (Figure 2). This pressure provides the loading
pressure to help the main valve spring keep the main
valve plug tightly shutoff.
An inlet pressure rise above the set pressure
overcomes the pilot control spring and opens the
pilot valve plug. Loading pressure bleeds out the pilot
exhaust faster than it can be replaced through the pilot
restriction. This permits inlet pressure to unbalance
the main valve plug and open the main valve. As inlet
pressure drops below set pressure, the pilot control
spring closes the pilot valve plug. Loading pressure
again builds up to close the main valve plug.
WARNING
Installation
Personal injury, equipment damage or
leakage due to escaping gas (or liquid)
or bursting of pressure-containing
parts may result if the relief valve is
installed where its capabilities can be
exceeded or where conditions exceed
any ratings of the adjacent piping or
piping connections. To avoid this, install
a Type 63EG-98HM relief valve where:
• Service conditions are within unit
capabilities (including those given in
the Specifications section)
• Service conditions are within applicable
codes, regulations or standards
Additionally, physical damage to the
relief valve could break the pilot off the
main valve, causing personal injury and
property damage due to escaping gas (or
liquid). To avoid such injury or damage,
install the unit in a safe location.
Figure 2.
Operational Schematic
3
Type 63EG-98HM
