Page 191 - Reciprocating Compressors Operation Maintenance

Operation and Maintenance of Reciprocating Compressors 1 77

Be sure rings are installed in proper order with identification
marks on ring segments facing the pressure.
2. Double Tangent Ring Set
This type consists of two tangent rings doweled together. This
assembly seals in either direction, making it double-acting. It is used
in vacuum applications, behind the vent, or for any other reverse
pressure purpose. This ring set normally requires a differential pres-
sure of 15 to 20 psi to obtain a good seal.
3. Pressure Breaker Type
This is the simplest form of packing ring and, because it does not
have overlapping or seal type joints, it acts to break or slow down

DOUBLE ACTING RING
EITHER SIDE MAY FACE PRESSURE

France Type 212
Cook Type BD

BO This is a double-acting sealing ring in that it
effects a seal regardless of the groove side
it contacts. It is intended to be used when
pressure is insufficient to continually hold
the ring against one face.

FIGURE 3-39. Double-acting sealing rings are bi-directional (Source: Wor-
thington Compressor Co., Service Manual).

gas passage only without actually sealing it completely. It is, there-
fore, in effect a form of labyrinth.
Note from Figure 3-40 that this ring may be installed with either
face toward the pressure and that it has a limited clearance at the cut
only. Some clearance at this point must always be maintained,
although it should not be greater than .010" per inch of bore diame-
ter. Obviously, this ring should not be allowed to operate without
end clearance because its life would be very short. Any wear that
takes place at the rod contact would tend simply to enlarge the bore