070.655-IOM (FEB 22)
Page 19
SBTP Rotary Screw Compressor
Operation
Operation
Operation and start-up instructions
The Frick SBTP rotary screw compressor is a compo-
nent in an integrated system. As a result, the compressor
requires some specific operation and conditions to ensure
trouble-free running.
The information in this section provides logical step-
by-step instructions to correctly start up and operate
the SBTP rotary screw compressor in your unit. It only
includes matters that may influence the correct operation
of the SBTP compressor.
Read and ensure you understand the following sections
before attempting to start or operate the unit.
Compressor hydraulic system
Note:
The solenoid valves and manifold block are
available as a sales order option.
The compressor hydraulic system actuates the movable
slide valve (SV) to load and unload the compressor. It also
actuates the movable slide stop (SS) to increase or de-
crease the compressor’s volume ratio (Vi).
The hydraulic cylinder located at the inlet end of the SBTP
compressor serves a dual purpose. It is separated by a fixed
bulkhead into two sections: the SV section is on the for-
ward side of the bulkhead and the SS is aft of the bulkhead
when viewed from the non-drive end of the compressor.
Both operations are controlled by solenoid valves, which
are actuated when a signal from the appropriate micropro-
cessor output energizes the solenoid valve.
Single-acting mode: high stage
Valve opens at SC1
Valve closes at SC2
Valve opens at bypass (BP)
for details.
High-stage compressor loading:
the compressor loads
when SV solenoid YY2 is energized and oil flows from the
unload side of the cylinder out port SC1, through valve
ports A and T to compressor suction. Simultaneously,
discharge pressure loads the slide valve.
High-stage compressor unloading:
the compressor
unloads when SV solenoid YY1 is energized and oil flows
from the oil manifold through valve ports P and A to cylin-
der port SC1 and enters the unload side of the cylinder. Si-
multaneously, gas on the load side of the cylinder is vented
through port SC2 and valve BP to compressor suction.
NOTICE
To control the rate of loading and unloading, throttle
the needle valve at SC1 port.
CAUTION
You must use single-acting mode for compressors
with differential pressures above 200 psid in order to
prevent failure of the slide valve piston retaining nut.
Double-acting mode: booster, low differential
Valve opens at SC1
Valve opens at SC2
Valve closes at BP
for details.
Booster compressor loading:
The compressor loads when
SV solenoid YY2 is energized and oil flows from the oil
manifold through valve ports P and B to cylinder port SC2
and enters the load side of the cylinder. Simultaneously,
oil contained in the unload side of the cylinder flows out
cylinder port SC1 through valve ports A and T to compres-
sor suction.
Booster compressor unloading:
The compressor unloads
when
SV solenoid YY1 is energized and oil flows from the
oil manifold through valve ports P and A to cylinder port
SC1 and enters the unload side of the cylinder. Simultane-
ously, oil contained in the load side of the cylinder flows
out of compressor port SC2 through valve ports B and T to
compressor suction.
NOTICE
To control the rate of loading and unloading, throttle
valves SC1 and SC2. Optional flow control valves are
available (FC1 and FC2) for finer speed adjustment.
NOTICE
To slow all valve movements - loading, unload-
ing, and Vi change - a optional customer supplied
throttle valve can be used upstream of connection P.
Figure 19: Solenoid valve block
Special throttling control valve blocks are available with
needle valves and check valves on each port direction.
You can order through Frick sales on new orders or parts
on aftermarket.
CAUTION
Never open valve BP and valve SC2 at the same time
during compressor operation.
