Renewed Understanding of Oil Scraper Rings, Couplings and Shaft Seals of Reciprocating Compressors
1. Oil Scraper Ring
The piston rod is fitted with oil scraper rings to isolate lubricating oil from the distance piece, piston rod packing area and cylinder section. Lubricating oil flows back to the crankcase sump via a U-tube at the guide bearing position. The distance piece separates the gas compression section from the oil-lubricated crankcase.
2. Coupling
The coupling assembly connects the flywheel and coupling hub through rubber elastic rings. The cast iron flywheel is connected to the crankshaft, while the ductile iron coupling hub is connected to the motor.
Couplings are classified into flexible couplings and rigid couplings. Flexible couplings are widely adopted in medium and small-sized compressors, whereas rigid couplings are mostly applied to horizontal balanced opposed compressor units.
3. Shaft Seal
A shaft seal generally refers to the sealing device installed at the position where one end of the compressor drive shaft extends out of the casing to connect with the driver. The spring-type shaft seal consists of a rotating ring, stationary ring, spring, spring seat, compression ring and O-ring seal.
The shaft seal chamber is filled with lubricating oil to lubricate the sealing surface between the rotating and stationary rings, reduce leakage and dissipate heat. The oil pump continuously delivers oil to the shaft seal, and the oil then flows through the oil passages on the crankshaft to the main journal and crank pin.
The shaft seal prevents compressed gas from leaking outward along the extended crankshaft end. In cases where the pressure inside the crankcase is lower than atmospheric pressure, it also prevents ingress of ambient air.
The piston rod is fitted with oil scraper rings to isolate lubricating oil from the distance piece, piston rod packing area and cylinder section. Lubricating oil flows back to the crankcase sump via a U-tube at the guide bearing position. The distance piece separates the gas compression section from the oil-lubricated crankcase.
2. Coupling
The coupling assembly connects the flywheel and coupling hub through rubber elastic rings. The cast iron flywheel is connected to the crankshaft, while the ductile iron coupling hub is connected to the motor.
Couplings are classified into flexible couplings and rigid couplings. Flexible couplings are widely adopted in medium and small-sized compressors, whereas rigid couplings are mostly applied to horizontal balanced opposed compressor units.
3. Shaft Seal
A shaft seal generally refers to the sealing device installed at the position where one end of the compressor drive shaft extends out of the casing to connect with the driver. The spring-type shaft seal consists of a rotating ring, stationary ring, spring, spring seat, compression ring and O-ring seal.
The shaft seal chamber is filled with lubricating oil to lubricate the sealing surface between the rotating and stationary rings, reduce leakage and dissipate heat. The oil pump continuously delivers oil to the shaft seal, and the oil then flows through the oil passages on the crankshaft to the main journal and crank pin.
The shaft seal prevents compressed gas from leaking outward along the extended crankshaft end. In cases where the pressure inside the crankcase is lower than atmospheric pressure, it also prevents ingress of ambient air.
