Data Sheet

Bulletin 71.4:MR98
9
FOR TYPES MR98HD, MR98HHD AND MR98LD WITH METAL
DIAPHRAGMS, ASSEMBLE DIAPHRAGM GASKETS UNDER AND
ABOVE THE METAL DIAPHRAGMS AS SHOWN ABOVE
SPRING METAL DIAPHRAGMS
GASKET
Figure 2. MR98 Series Operational Schematics (continued)
CONTROL SPRING
DIAPHRAGM
ORIFICE
VALVE PLUG
LOADING PRESSURE
INLET TAP
HANDWHEEL
CONTROL LINE TAP
TYPE MR98HD WITH INTERNAL PRESSURE REGISTRATION TYPE MR98HD WITH EXTERNAL PRESSURE REGISTRATION
OUTLET PRESSURE
INLET PRESSURE
LOADING PRESSURE
The differential relief valve responds to both controlled
pressure and loading pressure and opens or closes
as these pressures change. If the loading pressure
increases, pressure on the upper side of the
diaphragm increases. The valve plug moves closer
to the orice and restricts the ow through the relief
valve. When loading pressure decreases, pressure
on the upper side of the diaphragm decreases. This
allows the valve plug to move away from the orice
and allow more ow through the differential relief
valve (to atmosphere or back into the system). The
differential relief valve opens and closes in response
to changes in the controlled pressure. In this way, the
differential pressure between the controlled and outlet
pressures is maintained.
Capacity Information
Relieving capacities at selected pressures and outlet
pressure ows are given in SCFH (60°F and 14.7 psia)
of air in Tables 10, 11, 15, 16, 20 and 21. To determine
the equivalent capacities for other gases, multiply
the table capacities by the following appropriate
conversion factors: 1.29 for 0.6 specic gravity natural
gas, 0.808 for propane, 0.707 for butane or 1.018 for
nitrogen. For gases of other specic gravities, divide
by the square root of the appropriate specic gravity.
Then, if capacity is desired in normal cubic meters per
hour (Nm
3
/h) at 0°C and 1.01325 bar, multiply SFCH
by 0.0268.