Page 228 - Compression Machinery for Oil and Gas

Reciprocating Compressors Chapter 5 217

FIG. 5.36 Suction valve closing regulation. (Courtesy of Ariel Corporation.)

is required through the active suction valve. This removes active valve flow area
thus reducing the efficiency of this valve.
Suction valve closing regulation (Fig. 5.36) provides a mechanical means to
hold suction valves open past the point of the pressure-volume cycle where they
would normally close and remain closed during the compression portion of the
cycle. This allows suction gas to flow backward through the suction valves effec-
tively reducing the capacity of that pressure-volume cycle. Typical minimum
flows are to about 20% of a cylinder end’s capacity, or an 80% reduction. The
capacity is then completely variable between 100% and about 20% (Fig. 5.37).

Head-End Bypass
A head-end bypass is another mechanical device used to deactivate the head
end of a double-acting compressor cylinder. The device replaces the standard