When the operator pulls down on the retracting
lever, the force transmitted through the control cable
lifts the end of the retracting lever that is attached to the
return spring and tie rod. The retracting lever has a pivot
point on the block mounting of the valve. As the one
end of the retracting lever is lifted, the end connected to
the plunger pushes down on the plunger and valve stem,
allowing fluid flow through the valve from the
accumulator or fluid cooler to the engine cylinder, thus
forcing the ram and crosshead back to their battery
position. After retraction is complete, the retracting
lever is released and the return spring pulls down on the
retracting lever, which in turn pulls up on the plunger
and valve stem, which closes the valve. See figure 3-7.
The ideal condition is that tension be kept on the
purchase cable from the beginning of the retracting
stroke until the ram is in its battery position. An
interruption of the stroke generally disrupts this
condition and creates cable backlash, which results in
cable slack on the engine.
If an emergency arises involving the safety of
personnel or equipment, and an interruption of
procedures are recommended to prevent possible
damage, such as a tight kink, to the purchase cable:
Resume retracting very slowly at first to rid the
cable system of slack.
Resume full-speed retraction only after the
cable slack has been eliminated and the cable
Inspect sheave damper sheaves for proper
seating of the purchase cable on completion of
automobiles is installed on the operating lever to
eliminate chattering of the retracting valve during
LEARNING OBJECTIVE: Describe the
The Mk 7 Mod 3 arresting engine has a
recirculating-type hydraulic system. During arrest-
ment, the hydraulic fluid is forced from the main engine
cylinder, through the CRO valve, to the accumulator.
An initial air charge of 400 psi in the accumulator
builds up to approximately 650 psi during arrestment.
This increased pressure is used to force the fluid from
the accumulator into the fluid cooler, thus forcing fluid
from the previous arrestment, already cooled by the
cooler, out of the cooler, through the retracting valve,
and into the main engine cylinder, returning the engine
to its BATTERY position.
The accumulator (fig. 3-9) is a long, steel cylinder
mounted horizontally in saddles on the engine
structure, with the fluid end toward the fixed sheaves.
Inside the accumulator is a floating piston that
separates the air side of the accumulator from the fluid
side. The air end of the accumulator is flanged and
FLUID INDICATOR ROD
SLIPPER AND CAGE ASSEMBLY
LEVEL INDICATOR PLATE
Figure 3-9.The Mk 7 accumulator.