Figure 15 - Pressure Relief Valve - Cross Section
(6) Inspect all parts for wear, burrs, etc. Be sure all gaskets and seals are in good condition. Replace if questionable.
(7) Before re-assembling, clean all parts thoroughly so that no foreign particles are introduced into the valve and
Re-setting Relief Pressure
To re-set the valve for 1500 PSI relief, proceed as follows:
(a) Back-off (counterclockwise) adjusting screw (C) so that the valve will by-pass fluid at low pressure.
(b) Install an accurate pressure gauge in the gauge port at the rear corner of the engine radiator shroud.
(c) Run engine at Full speed.
(d) Hold hopper wing switch at UP position and turn valve adjusting screw (C) inward (clockwise) to slowly raise
gauge pressure to 1500 PSI. Hold screw (C) and tighten locknut (B). Re-check gauge for 1500 PSI after tightening
(e) Hold hopper wing switch at DOWN position to re-check relief setting. Repeat test several times.
(f) Install valve cap (A).
(17) Throttle Valve - (See Figure 16) - Throttle valves are used in the "down" phase of the screed lift system and
in both phases of the optional truck hook system. The throttle valve in a two directional line allows unrestricted flow in
one direction and metered or restricted flow in the opposite direction. In the case of the screed lift, the flow in the RAISE
direction is unrestricted while the return flow in the LOWER direction is restricted by a 3/32" DIAM. orifice. This permits
the screed to raise at moderate speed but to descend at a slower safe rate. A drilled poppet is the only moving part. The
valve can be easily disconnected for examination of the orifice for presence of foreign matter. The orifice can be probed
clear using a piece of 1/16" diam. wire. If probing succeeds in clearing a blockage the valve should then be removed
from the line and flushed clean of particles.
Figure 16 - Throttle Valve - Cross Section
(18) Hydraulic Cylinders - (See Figures 17 & 18) The hydraulic cylinders used on Cedarapids pavers are
selected for efficient service and maximum durability. Very little trouble is normally experienced unless the hydraulic
fluid is contaminated by foreign particles which find their way into cylinders and cause rapid seal wear. Heavy duty wiper
type seals for the exposed rods help to minimize contamination. These parts should be maintained in top condition.
If severe contamination of the hydraulic fluid has occurred and it is likely that a large quantity of particles has reached the
cylinders, it is wise to flush them thoroughly with a suitable solvent. Replace seals when worn so that leakage is not a
threat to efficient system operation.
A worn piston seal will permit leakage of fluid around the seal from the pressure to the discharge side of the
cylinder. The result is sluggish movement of the piston rod or a failure to maintain rod position. Seal replacement is the