Clearance is the volume remaining in a cylinder end when the piston is at the end of its stroke. This is the sum of the volume between the head of the cylinder and the piston, and the volume under the valve seats. The total clearance is expressed in percent of the total piston displacement, normally …
Read More…Category: Reciprocating Compressors – Components
Reciprocating Compressors – Valve Unloaders
Inlet valve unloaders are used to deactivate a cylinder end and reduce its capacity to zero. Two of the more common types of unloaders are depressor-type unloaders and plug-type unloaders. Depressor-type unloaders hold the inlet valve open during both the suction and discharge strokes so that all the gas is pushed back through the inlet …
Read More…Reciprocating Compressors – Valves
The compressor valves control the flow of gas into and out of the compressor cylinder. All valves are similar in that the differential pressure across the seat must be greater than the balance spring force before gas may flow through the valve. The lift characteristics, seat area, and flow areas determine the advantages of each …
Read More…Reciprocating Compressors – Packing
Packing provides the dynamic seal between the cylinder and the piston rod. It consists of a series of Teflon rings mounted in a packing case, which is bolted to the cylinder. The piston rod moves in a reciprocating motion through this case. Figure 11-13 shows a typical packing case. The packing case is constructed of …
Read More…Reciprocating Compressors – Bearings
Most field compressors use hydrodynamic type or “journal” bearings. As shown in Figure 11-12, oil enters into the bearing from supply holes strategically placed along the bearing circumference and builds up an oil film between the stationary and rotating parts of the bearing. The oil flows axially and circumferentially along the bearing, then out the …
Read More…Reciprocating Compressors – Piston
The piston is located at the end of the piston rod and acts as a movable barrier in the compressor cylinder. It is generally made from materials such as aluminum or cast iron and has a hollow center. Small-diameter high-pressure cylinders may be provided with a combined piston and rod machined from a single piece …
Read More…Reciprocating Compressors – Crosshead, Rods, and Crankshaft
The crosshead converts the rotating motion of the connecting rod to a linear, reciprocating motion, which drives the piston as shown in Figure 11-10. The crosshead is provided with top and bottom guide shoes, which ride on lubricated bearing surfaces atached to he compressor frame. In addition, balance weights may be attached to the crosshead …
Read More…Reciprocating Compressors – Distance Pieces
A distance piece provides the separation of the compressor cylinder from the compressor frame as shown in Figure 11-9. At the top of the figure is a standard distance piece. The piston rod moves back and forth through packing that is contained within the distance piece. The packing keeps the compressed gas from leaking out …
Read More…Reciprocating Compressors – Special Compressor Cylinder Construction
Many variations and combinations of cylinder types and arrangements are available from the compressor manufacturers. The compressor manufacturer will generally make its selection based on the most economical combination it has available. Figure 11-7 is a cut-away of a steeple cylinder. This cylinder design is actually two single-acting cylinders coupled together with different-size pistons on …
Read More…Reciprocating Compressors – Frame
The compressor frame, shown in Figure 11-2, is a heavy, ragged casting containing all the rotating parts and on which the cylinders and crossheads are mounted. All frames are rated by the compressor manufacturers for a maximum continuous horsepower, speed (rpm), and rod load. The rated horsepower is determined by the maximum horsepower that can …
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