DeZURIK
APCO CSD-800 Slanting Disc Check Valves
D12012
Page 14
July 2017
Operation of Internal Cushion
The cushioning of a hydraulic cylinder stroke is obtained by trapping the exhaust oil as the piston
assembly nears the end of its stroke. In Figure 4, as the Cushion Plunger (1) enters Cushion Cavity
(2), the exhaust oil is almost completely trapped by the Ball Check (3) and the Adjusting Screw (4)
creating a back pressure against Piston Assembly. The back pressure cushions and slows the final
part of the Piston stroke, thus reducing the high impact hammering of the Piston Assembly against the
Cylinder Cap.
Turning the Adjusting Screw to allow more or less oil to escape regulates the degree of cushioning as
desired.
In Figure 5, when oil enters the Cylinder Cap End to stroke the Piston Assembly in the opposite
direction, the oil moves the Ball Check (3) off it seat, opening the passage for more oil to act against the
Piston, thus speeding its start-up movement as the Cushion Plunger (1) is immediately forced out of its
cavity (2).
Figure 4: Cushion
“IN” Stroke
Figure 5: Cushion
“OUT” Stroke
Oil Filling Procedure
CSD-800-BMB Valves
-See Figure 1
1.
Hydro-pneumatic tank
(32)
a. Shut down pump.
b. Release air pressure of hydro-pneumatic tank and remove pipe plug located on the side
of the tank and also either the Pressure Gauge (32B) or Air Valve (32A).
c. Fully open Flow Control Valve (41B) and slowly fill cylinder with SAE 20 oil or equivalent
until it spills out of the side port. This is the oil fill level.
d. Replace both fittings and pressurize tank according to the formula;
Tank pressure = Line pr 5 psi
4
e. Set flow control valve three turns counterclockwise from fully closed position.
f. Start pump and observe if buffer rod (33) extends. If not, while valve is still open add
more pressure in increments of 5 PSI until rod fully extends.