Cylinder Action, Single Acting
A single acting cylinder
compresses gas on only either the instroke or outstroke of the piston.
Double acting cylinders can be operated in a single acting mode by removing
the suction valves from one end or by using valve plate depressor type
suction valve unloaders.
Below is a drawing of cylinder
with a suction valve unloader on the head end suction valve for deactivating
the head end. Ariel requires installing suction valve unloaders on all
suction valves of a cylinder end to be single acted to reduce horsepower
losses.
In order to maintain proper rod
load reversal, the head end of the cylinder is usually deactivated. This
will help maintain rod load reversal due to the differential areas between
the crank end and the head end of the cylinder (due to the rod area in
the crank end). In some cases it is possible to deactivate the crank end
and maintain rod load reversal due to the inertia load.
Single acting cylinder operating
cases should be included in the analyses for torsional
responses and acoustical pulsation responses. Single
Acting cylinders can present the worst case scenario for a torsional analysis
due to a more dynamic torque effort curve and for an acoustical pulsation
analysis due to a change in the number of pulses per cycle. High
torsional vibration and / or high acoustically driven vibration can result
from single acting cylinder operation when not considered in these analyses.
Some restrictions may apply to
operating a cylinder single acting at higher speeds. The
performance software should flag higher speed single acting conditions
that require review and approval
Capacity control sequencing can
be very important when considering single acting operating cases. Capacity
control sequences are discussed within the Capacity
and Load Control topic.
Ariel
Corporation Application Manual
7 March 2008