Page 192 - Reciprocating Compressors Operation Maintenance

178 Reciprocating Compressors: Operation and Maintenance

.TOTAL OPENING AT ONE
CUT ONLY" ROD 01 A. X .010" MAX.
DOUBLE ACTING RING
EITHER SIDE MAY FACE PRESSURE
France Type 250
Cook Type P

P A P' style ring is the standard pressure breaker
incorporated in most ring sets. Flow past the
ring is maintained by control of end clearance.
PA This ring is same as a "P". but flow control is
accomplished through clearance between
ring I.D. and the rod.

FIGURE 3-4O. Standard pressure breaker ring (Worthington Compressor Co.
Service Manual).

of the ring, and it would dangle. The most important function of
breakers in compressor service is to retard backflow from the pack-
ing case toward the cylinder on the intake stroke.
4. Radial, Tangent, and Back-Up Set
This is the basic sealing unit used in higher pressure lubricated and
non-lubricated compressors, where Teflon (PTFE) ring material is
used and is a combination of three rings in one cup (see Figure 3-41).
It is made up of one radial and one tangential packing ring, with
one radial-cut back-up ring completing the combination. The radial
packing ring is installed in the groove on the pressure side toward
the cylinder. The tangential-cut ring is installed between the radially
cut packing ring and the back-up ring.
The back-up ring may be metallic or Teflon and is bored .003"
per inch of outside diameter larger than the piston rod. It has butted
ends with zero gap clearance and does not grip the rod under pres-
sure loading. Its function is to prevent extrusion of the Teflon mem-
ber of the packing rings and to conduct heat away from the rod sur-
face by light contact with the rod.