Page 290 - Reciprocating Compressors Operation Maintenance

Overhaul and Repair of Reciprocating Compressors 275

• Solid rider rings or bands are made in one piece and are machined
with an interference fit so that, once expanded over the piston end,
they will contract like a rubber band to provide a snug fit on the pis-
ton. This type does not require pressure relief grooves.

The life of solid rider bands can be extended by rotating pistons 120°
to 180° at each overhaul.

Rider Ring Clearances

The suggested minimum side and end clearances for rider rings of dif-
ferent materials are shown below.

TABLE 4-5
MINIMUM SIDE AND END CLEARANCES FOR RIDER RINGS
OF DIFFERENT MATERIALS

Side Clearance End Clearance
Material (Per inch of width) (Per inch of cylinder diameter)
Cast Iron .001" (.002" min.) .015"
Bronze .001"(.002"min.) .015"
Teflon .012" .035"
Carbon .001" .015"

The clearances shown in Table 4-5 are for butt cut or step joint rings as
shown in Figure 4-27. For angle cut joints multiply value in table by the
amounts shown in Figure 4-28.
The side clearance for Teflon rider rings, which must be stretched to
install, applies after installation.

Visual inspection of the piston is recommended at every shutdown or
whenever a valve is removed. While it is not possible to inspect the entire
piston through the valve ports, enough can be seen to determine if any
scuffing is occurring. This partial inspection gives an indication of piston
problems and further corrective action can be taken, if needed.