Page 110 - Compression Machinery for Oil and Gas

98 SECTION II Types of Equipment

prevent the seal oil from entering the process stream and to reduce the amount of
oil contamination. Little to no gas leakage occurs across the actual seal. Most
emissions are actually from seal oil degassing due to the oil absorbing gas on the
inboard side.
The sweet uncontaminated oil is drained back directly to the reservoir. The
contaminated oil is sent to a separate drain cavity and is either discarded or
degassed. If the contaminated oil is reconditioned, it must first be sent to a
degassing tank to release the entrained gas by heating the oil. This eliminates
the possibility of contaminating the fresh lube and seal oil reservoirs. Then, the
degassed oil is sent directly to the reservoir to be reused. The released gas may
be vented, flared, returned to the compressor inlet, or used as fuel in some cases.
The main purpose of the seal oil supply system is to supply clean, cool oil to
the seals at the required pressures and flows. The system generally consists of an
oil reservoir, oil pumps, coolers, filters, and regulators to precisely control the
pressures and temperatures required for the compressor seals. Fig. 3.64 is a typ-
ical oil supply system for a mechanical face seal. For cost and space savings
the seal system may be incorporated with the lubrication system to allow for
additional oil capacity and flows.

FIG. 3.64 Seal oil supply system for mechanical face seal [21].