Multiquip ST70 - Manual (Page 85)

ST-70 — PARTS & OPERATION MANUAL — REV. #4 (05/29/07) — PAGE 85
ST-70 — SERVICE INFORMATION
ST-70 Accumulator Circuit
The accumulator circuit has two functions in the hydraulic
system.
1. The accumulator circuit furnishes the hydraulic pressure
to cycle the shuttle tube.
2. The accumulator circuit also furnishes the pilot pressure
necessary to activate the hydraulic system.
The accumulator circuit is equipped with a bladder type
accumulator charged with 1100 PSI of dry nitrogen. The
accumulator stores one gallon of hydraulic oil, which is, under
1750 PSI of pressure. When the pump cycles, a part of the
stored oil is released to the shuttle cylinder, this pressure release
assures the shuttle tube has enough force to shear the cylinder
of concrete passing from the concrete cylinder to the concrete
delivery line during the cycle phase.
Setting pressures in the accumulator circuit
Attach 3000 PSI test gage to port 2-G of the main control block.
(Pressure test gauge Mayco P/N 98016)
The unloading valve cartridge, located in port 4-E, loosen lock
nut and with an allen wrench turn adjusting screw clockwise
until it is completely closed.
Turn the pump switch and run engine at 2350 Rpm’s and adjust
the accumulator circuit pilot relief valve cartridge, located at
port 4-G. Loosen lock nut, turn allen adjusting screw until
pressure gauge reads 1950 PSI, and tighten lock nut. Turn engine
off and on several times to make the pressure continues to read
1950 PSI. With relief valve set at 1950 PSI it is time to adjust the
unloading cartridge. Turn on pump and run at 2350 Rpm’s and
maximum volume. Using the accumulator pressure gauge
located by control panel, adjust unloading valve cartridge
counter clockwise until the pressure reaches 1750 PSI. Start
and stop pump several times to make sure accumulator circuit
pressure is holding at 1750 PSI. At this time tighten lock nut on
unloading valve cartridge. Your accumulator circuit pressure
should now be properly adjusted.
Checking accumulator bladder pressure
The accumulator charge pressure should read 1100 PSI. To
check pressure, start engine and stroke the pump. The
accumulator pressure gauge should read 1750 PSI. To
determine the actual accumulator PSI, stop engine and observe
the pressure gauge. As the PSI reading slowly decreases it will
reach a point where there will be a sudden drop in the PSI. The
PSI reading should be taken prior to this sudden drop. If you do
not read 1100 PSI the accumulator may require charging or
bladder replacement.
Warning – Explosion caused by improper accumulator
charging can result in serious injury or death! Never use oxygen
or compressed air to charge the accumulator! Only qualified
personal should perform this procedure. Use only dry nitrogen
to charge the accumulator. Contact your Mayco service
department or your local Hydac representative for proper
charging procedure.