Page 186 - Reciprocating Compressors Operation Maintenance

172 Reciprocating Compressors: Operation and Maintenance

tangent ring. The gaps in the radial ring provide access for pressure
buildup and relief over the ring's outside diameter.

How COMPRESSOR PACKING WORKS

As previously described, a packing set consists of a series of sealing
units. Compressor packing is not bottle-tight, but the amount of leakage is
extremely small, a fraction of one percent of the capacity of the machine
and usually within tolerable limits. In case of toxicity of the gas or danger
of explosion or corrosion, leakage may be vented to a safe place.
Because the individual rings will leak slightly, it is through the series of
rings that the pressure is broken down from discharge to atmosphere (see
Figure 3-32). The higher the pressure, the more seal rings will be required.
The volume of leakage will increase with an increase in the differential
pressure across the rings. It will also increase with the time that the dif-
ferential pressure exists. In other words, the higher the differential pres-
sure and the longer the differential exists, the greater will be the volume
of leakage.

4MB-.

4,000 PSI PACKING
FIGURE 3-32. Conventional packing cases for different pressure levels
(Source: C, Lee Cook, I^ouisville, Kentucky).