The internal moving parts are often called the running gear. A typical set of running gear is shown in Figure 300-18. Note that a balancing weight(s) (usually a circular plate, not shown) can be added at the threaded end of the crosshead.
Lubrication of Running Gear. Lubrication is normally accomplished with a pressurized system using the sump of the compressor frame as the reservoir. API 618 describes requirements for the system components. Although many systems do not necessarily meet the requirements of API 618, the diagram included in API 618 shows a typical system schematic arrangement.
Whether a single oil filter or duplex filters are to be furnished is usually a matter of plant preference, based on the criticality of the service and number of machines applied to the service. Unlike centrifugal-compressor systems, twin oil coolers are seldom used in reciprocating compressor systems.
Splash type systems are sometimes used to lubricate the running gear of smaller machines (200 HP or less).
Compressor cylinder and packing lubrication is provided with force-feed mechanical lubricators. There are two types of lubricator systems: the multiple pump type (also called “single-plunger-per-point”), and the distributor type (also called “divider block”).