Overpressure Protection; Startup - Fisher MR95L Instruction Manual

MR95 Series

Overpressure Protection

WARNING
!
Personal injury, equipment damage or
leakage due to escaping accumulated gas
or bursting of pressure-containing parts
may result if this regulator is:
• Overpressured
• Installed where service conditions
could exceed the limits given in the
Specifications section and on the
appropriate nameplate
• Where conditions exceed any ratings of
adjacent piping or piping connections
To avoid such injury or damage, provide
pressure-relieving or pressure-limiting
devices to prevent service conditions from
exceeding those limits.
The Types MR95H and MR95HD regulators have an
outlet pressure rating equal to the inlet pressure rating.
The Types MR95L, MR95LD, MR95HP and MR95HT
regulators have an outlet pressure rating lower than
the inlet pressure rating.
The recommended pressure limitations are
stamped on the regulator nameplate. Some type of
overpressure protection is needed if the actual inlet
pressure exceeds the maximum operating outlet
pressure rating. Provide external overpressure
protection if the regulator inlet pressure is greater than
the safe working pressure of downstream equipment.
Common methods of external overpressure protection
include relief valves, monitoring regulators, shutoff
devices and series regulation.
Regulator operation below the maximum pressure
limitations does not preclude the possibility of damage
from external sources or from debris in the pipeline. If
the regulator is exposed to an overpressure condition,
inspect it for any damage that may have occurred.

Startup

The Specifications section and Tables 3
and 4 show the maximum inlet, the
differential and the outlet pressures for
12
Note
specific constructions. Use pressure
gauges to monitor inlet pressure, outlet
pressure and any loading pressure
during startup.
1. Check that proper installation is completed
and downstream equipment has been
properly adjusted.
2. Make sure all block and vent valves are closed.
3. Decompress the control spring by turning the
adjusting screw (for Types MR95L, MR95H,
MR95HP and MR95HT) or handwheel (for
Types MR95LD and MR95HD) counterclockwise.
4. Slowly open the valves in the following order:
a. Loading supply and control line valve(s), if used
b. Inlet block valve
c. Outlet block valve
5. Set the regulator to the desired outlet (control)
pressure according to the Adjustment procedure.
Adjustment
WARNING
!
To avoid personal injury, property
damage or equipment damage caused
by bursting of pressure containing parts
or explosion of accumulated gas, never
adjust the control spring to produce an
outlet pressure higher than the upper
limit of the outlet pressure range for that
particular spring. If the desired outlet
pressure is not within the range of the
control spring, install a spring of the
proper range.
The factory setting of the regulator can be varied
within the pressure range stamped on the nameplate.
Follow the following procedures for the proper
adjustment of the outlet (control) spring. If the spring
range was changed, be sure to change the stamped
spring range on the nameplate.
All MR95 Series regulator springs can be backed off
to provide zero outlet. Recommended outlet pressure
ranges available, maximum inlet pressures and color
codes of the respective springs are shown in Tables 3
and 4.