BLACKMER HD942A, Installation, Operation And Maintenance Instructions

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INSTALLATION
CB9A-030 page 7/28
SUCTION VALVE UNLOADERS
Compressors may be fitted with suction valve unloaders
to provide loadless start or capacity control functions.
Blackmer unloaders are basically a piston and a plunger
atop the suction valve. When pressure is applied to the
top of the unloader piston, it and the plunger move
downward, pushing the suction valve off its seat and
unloading the compressor. When the pressure signal is
removed, the unloader spring pushes the piston and
plunger back up and the suction valve will resume
normal operation.
1. In order for the unloaders to function, the unloader
pressure must be at least 30 psi (2.1 Bar) above
suction pressure.
2. Do not operate unloaders for longer than 10
minutes as gas recirculation through the suction
valves will cause overheating.
Hazardous gases
can cause property
damage, personal
injury or death
Excessive gas recirculation using
suction valve unloaders can be a source
of ignition in explosive atmospheres
causing severe personal injury or death
3. Do not place a restrictive device such as a back
check valve in the suction line near the compressor.
If such a device must be installed, the volume in the
piping between the device and the compressor
must be at least 10 times the cylinder swept
volume.
WATER-COOLED COMPRESSORS
NOTICE:
DO NOT OPERATE WATER-COOLED UNITS
WITHOUT WATER FLOW!
Cooling water should be clean and at not more than
100 psig (6.90 Bar-g). A flow of 1 gpm (4 lpm) is
normally adequate. In general, cooler water
temperatures are preferable. However, care must be
taken as condensation may occur inside the
compressor if the water is too cold. Such condensation
can cause corrosion or even destroy the compressor.
Figure 4 - HDL942 Water Conntections
MAXIMIZING COMPRESSOR LIFE
Life of critical compressor components such as piston
rings, valves and packing will vary considerably with
each application, installation, and operating procedures.
Premature failure of wear parts can often be attributed
to one of the following causes:
1.
Excessive Temperatures
Primary causes are:
•
Operating at pressures other than those originally
specified.
•
Handling a different gas than originally specified.
•
Clogged strainer or filter elements.
•
Line sizes too small, or other flow restrictions.
•
Excessive ambient temperature or suction gas
temperature.
•
Valve problems. (See Foreign Material.)
•
Badly worn piston rings. (See Foreign Material.)
Lower operating temperatures will increase valve
and piston ring life significantly.
Hazardous gases
can cause property
damage, personal
injury or death
Extreme temperatures caused by
abnormally high discharge pressure or
valve problems can be a source of
ignition in explosive atmospheres
causing severe personal injury or death.
2. Foreign Material
Solid particles in the gas stream will:
•
Rapidly wear the piston rings and score the
cylinder wall.
•
Destroy the rod packing causing excessive
leakage and score the piston rods.
•
Lodge in the valves causing loss of capacity and
broken valve plates and springs.
Liquid in the gas stream will:
•
Cause broken valve plates and springs.
•
Destroy the compressor if present in sufficient
quantity.
On new installations, it is suggested that the valves
and piston rings be inspected after the first few
hundred hours of operation. This will give an early
indication of any abnormal problems and allow for
corrective action to be taken before a costly failure
results. Although piston ring life will vary from
application to application, wear will be fairly
consistent on subsequent sets of rings.