Page 70 - Reciprocating Compressors Operation Maintenance

Design and Materials for Reciprocating Compressor Components 57

Two piece, aluminum or cast iron, which is split for ease of hollow
casting and weight control. These are generally used above 10" bore
diameters. Aluminum is used when the reciprocating weight must be
reduced (Figure 2-15B).
Three piece, in which a ring carrier is added to permit band-type rider
rings to be installed directly into the piston grooves. While this design
adds a part, it allows thicker rings to be used since the ring does not have
to be stretched over the outside diameter. It is also used as a carrier for
the piston rings on large diameter pistons, where metallic rings are used
which might wear into an aluminum piston. Aluminum is used when
weight reduction is required. A cast iron ring is used for its superior ring
groove wall wearing qualities (Figure 2-15 C).

Piston Materials

Material selection for pistons is very important, and many factors must
be considered. Some of these include

• Weight
• Strength, for differential pressures and inertia forces
• Corrosion resistance
• Compression and rider ring wall wear resistance
• Outside diameter wear resistance

COMPRESSOR PISTONS

Figure A Figure B Figure C
Conventional small dlame- Two piece small diameter Three pleas piston with two
ter piston without rider piston with single rider rider rings. This design
rings. Material: Iron, ring. Material: Iron, stool, utilizes two rtder ring car-
steel or aluminum. Single aluminum or combinations rlere and one piston ring
bolt piston to rod attach- thereof. Single bolt piston carrier. Materials as In B.
men I, to rod attachment. Single bolt piston to rod
attachment.
FIGURE 2-t5. Typical piston designs (Source: Anglo Compression, Mount
Vernon, Ohio).