Page 223 - Reciprocating Compressors Operation Maintenance

TABLE 3- 12
OPERATION CHART FOR TWO-STAGE COMPRESSOR WITH FIVE-STEP CONTROL
Load Position Trouble Checks
Low High
Lights Capacity Operation Intercooler Pressure Intercooler Pressure

No Lights Zero All suction valves held open High pressure discharge
Clearance pockets closed valves faulty
(Pressure continues to
build up)
One Light 25 % Head end suction valves held Crank End Crank End
open Low pressure discharge High pressure suction
Crank end suction valves closed valves faulty valves faulty or
Clearance pockets open Crank End unloader stuck open
Low pressure suction Crank End
valves faulty or unloader High pressure discharge
stuck open valves faulty
Two Lights 50% Head end suction valves Head End
closed Low pressure discharge Head End
Crank end suction valves valves faulty High pressure suction
held open Head End valve faulty or unloader
Clearance pockets closed Low pressure suction stuck open
valves faulty or un- Head End
loader stuck open High pressure discharge
valve faulty
Three Lights 75% Head end suction valves If low also at 25% If high also at 25% but
closed capacity but good at good at 50%, same check as
Crank end suction valves 5096, same check as for for 25% capacity
closed 25% capacity If good at 25% but high
Clearance pockets open If good at 25% but low at 50% also, same check as
at 50% also same check for 50% capacity
as for 50% capacity
Four Lights 100% Head end suction valves If also low at 25% and If also high at 25% and 75% but
closed 75% capacity but good at 50%, same check as
Crank end suction valves good at 5096, same check for 25%
closed as 25% If also high at 50% and 75%
Clearance pockets closed If also low at 50% and same check as for 50%
7596, same check as for If high also at 50% only,
25% same check as for 50%
If low also at 50% only,
same check as for 50%
Note: Faulty valves refer to incorrect installation, bad gaskzt, or broken strips.