INSTALLATION
588/A page 8/24
RELIEF VALVES
A relief valve of a type, material and pressure rating
suitable to the installation, MUST be installed. The
relief valve shall be installed in the discharge line
between the compressor head and the first block valve.
Hazardous pressure
can cause serious
personal injury or
property damage
COMPRESOR OPERATING AGAINST
CLOSED VALVE CAN CAUSE SYSTEM
COMPONENT FAILURE, PERSONAL
INJURY OR PROPERTY DAMAGE.
Since all systems differ in design, care must be taken to
ensure the relief valve is installed to safely vent away
from sources of ignition and personnel. This can be
accomplished by either orientation or a pipe away,
consult the Relief Valve manufacture for assistance.
Hazardous gases
can cause property
damage, personal
in
r
r
th
OPERATION OF THE RELIEF VALVE
CAN RELEASE EXPLOSIVE GAS TO
THE ATMOSPHERE CREATING AN
EXPLOSION HAZARD, POSSIBLY
CAUSING PERSONAL INJURY OR
DEATH
Should the Relief Valve actuate, the cause MUST be
determined and corrected before continuing operations.
See the 'Troubleshooting' section.
Blackmer offers various relief valves for gas
compatibility:
•Brass for LP-Gas service
•Aluminum for anhydrous ammonia
•Steel, A.S.M.E. code stamped for both services,
and other applications.
LIQUID TRAPS
Compressors handling gasses that contain
condensates or other liquids MUST be protected from
entry of the liquid. While the use of liquid traps is
recommended, many operators of transports do not use
them. To prevent liquid from entering the compressor
and causing major damage, it is necessary to carefully
consider the system design and have strict procedures
for operation.
NOTICE: Liquid in the compressor cylinder can
cause destruction of the compressor.
Blackmer offers a variety of liquid traps. The most
common variations include:
1. A non-code vessel fitted with a stainless steel float
which will shut off the intake line to the compressor
in the event of an excessive liquid level. A vacuum
breaking valve is provided on the liquid trap head in
case the trap closes and a vacuum develops
between the compressor and the trap. A manual
drain valve is provided.
2. The above trap is fitted with an port allowing the
use of an electric float switch which protects the
compressor by stopping the compressor when a
high liquid level is present in the liquid trap. The
electric float switch may be used with or without the
mechanical float described above.
3. For additional protection, a larger ASME code
stamped vessel is available. This liquid trap is
typically fitted with one or two electric float switches
for both a high liquid level shut down and alarm
signal, a relief valve, and a manual drain valve.
Level gauges and automatic drain systems are
available options.
4-WAY VALVES
Many liquefied gas compressors are used for both liquid
transfer and vapor recovery operations. An optional 4-
way valve is used to reverse the direction of flow
through the system when changing from liquid transfer
to vapor recovery. Both lubricated and nonlubricated
models are available. Lubricated models should be
lubricated every 6 months.
TEMPERATURE SWITCHES
Excessive discharge temperature is a leading cause of
premature component failure and is often an early
warning sign of impending problems.
Optional temperature switches should be installed with
a thermowell as close to the compressor discharge as
possible. The switch should be set to actuate at a
temperature just above the maximum operating
temperature of the compressor.
LOW OIL PRESSURE SWITCHES
Loss of crankcase oil pressure is a rare occurrence, but
can result in costly damage. An optional low oil
pressure switch set at about 15 psig (1 bar-g) may be
installed to shut down the compressor in the event of a
lubrication failure. A 10 second delay timer should be
used to lock the low oil pressure switch out during
compressor startup.
Figure 7 - Typical Liquid Trap
