Carrier TRANSICOLD 05G, Операция и обслуживание, Страница: 10 / 23

1-6
SUCTION PRESSURE
DISCHARGE PRESSURE
1
2
3 4 5 6 7 8
9 10 11 12 13
14
15
16
1. Solenoid Valve
2. Coil
3. Capacity Control
Valve (Closed)
4. Unloader Piston
5. Unloader Head
6. Valve Body
7. Valve Spring
8. Cover Plate
9. Suction Manifold
10. Suction Valve
11. Piston
12. Discharge Valve
13. Discharge Manifold
14. Valve Plate
15. Strainer
16. Bleed Orifice
Figure 1-8. Compressor Cylinder Head (Loaded) ---
Suction Cutoff
1.5.3 PRESSURE-OPERATED UNLOADERS
There are two types of compressor unloader systems;
the first one is the hot gas bypass and the second is the
suction cutoff. They are easily distinguished from each
other by observing the bottom side of the compressor
cylinder head, it is either blank (Hot gas bypass) or has a
cover plate (Suction cutoff).
The two types of compressor unloader systems can
be controlled with either a pressure actuated valve or an
electrically actuated (solenoid) valve.
The pressure---operated unloaders are controlled by
suction pressure and actuated by discharge pressure. The
unloader valve controls two cylinders. On startup,
controlled cylinders do not load up until differential
between suction and discharge pressure is 10 psi (1.7
kg/cm
@
).
During loaded operation , when suction pressure is
above the valve control point, the poppet valve will close.
Discharge gas bleeds into the valve chamber; the pressure
closes the bypass piston; and the cylinder bank loads up.
Discharge gas pressure forces the check valve open,
permitting gas to enter the discharge manifold. See
Figure 1-9.
1
2
3 4
1. Sealing Cap
2. Pressure Differential Adjustment Screw
3. Control Set Point Adjustment Nut
4. Poppet Valve
Figure 1-9. Pressure-Operated Unloader
Loaded Operation
During unloaded operation , when suction pressure
drops below the valve control point, the poppet valve will
open. Discharge gas bleeds from behind the bypass piston
to the suction manifold. The bypass piston opens,
discharge gas is recirculated back to the suction manifold
and the cylinder bank is unloaded. Reduction in
discharge pressure causes the check valve to close,
isolating the cylinder bank from the discharge manifold.
See Figure 1-10.
1
2
3 4
1. Sealing Cap
2. Pressure Differential Adjustment Screw
3. Control Set Point Adjustment Nut
4. Poppet Valve
Figure 1-10. Pressure-Operated Unloaded ---
Unloaded Operation