Page 86 - Reciprocating Compressors Operation Maintenance

Design and Materials for Reciprocating Compressor Components 73

By far, the best non-lubricated compressor design is one embodying
labyrinth pistons. These are primarily available from Sulzer-Burckhardt
(Winterthur, Switzerland). They merit special consideration and are dis-
cussed at the end of this chapter.

DEFINITION OF NON-LUBRICATED CYLINDERS

Field references to non-lubricated compressors are often misleading,
so a definition of cylinder terminology is in order.
Since the cylinder assemblies of reciprocating compressors must be
designed relative to their lubrication, the nomenclature used to describe and
classify the types of cylinder construction likewise refers to lubrication.
The classifications most commonly used are

1. Lubricated Cylinder Construction—The lubricated cylinder
assembly is the conventional cylinder construction, which has a liq-
uid lubricant introduced directly into the cylinder and piston rod
packing in sufficient amounts to provide a lubrication film between
the mated parts. Previous descriptions have been made of this gen-
eral construction.
The gas stream from the lubricated cylinder is contaminated with
the lubricant, normally a hydro-carbon or a synthetic oil.
2. Mini-Lube—A partially lubricated cylinder construction with oil feed
to the cylinders reduced to at least one-third of that for a lubricated
cylinder. Teflon trim is used on the piston and for the pressure packing.
The aims of Mini-Lube construction are to reduce the amount of
oil carried within the exit gas stream and to reduce contamination of
downstream systems. Reduction in the amount of oil used and
reduction of load on downstream oil separation reduces costs.
3. Micro-Lube—No lubrication to the cylinder from conventional oil
feed, but some oil enters the cylinder from migration along the pis-
ton rod.
Teflon trim is used on the piston and for the pressure packing.
The oil scraper rings are usually removed, which allows oil migra-
tion along the piston rod.
The reasons for this construction are the same as for Mini-Lube,
except that the system receives an even smaller amount of oil.
4. Non-Lube or Oil-Free Cylinder Construction—No lubrication
reaches the cylinder. A longer distance piece is used to separate the