Multiquip ST70 - Manual (Page 88)

PAGE 88 — ST-70 — PARTS & OPERATION MANUAL — REV. #4 (05/29/07)
ST-70 — SERVICE INFORMATION
Changing the concrete cylinder piston cups
The Rubber piston cups will occasionally require replacement
depending on the following factors.
■ The fluid level and cleanliness of the lubrication box.
■ The size and type of aggregate.
■ The type of concrete being pumped.
It is time to replace the cups when increasingly large particles of
sand and cement pass into the lubrication box. Do not allow the
cups to become so worn that they begin to pass lubrication into
the material cylinders. If the liquid level of the lubrication box
becomes to low, the rubber cups will severely deform due to
excessive heat. Whenever replacement is due, both cylinder
cups should be replaced.
The following procedure should be used to replace the rubber
cups and felt rings.
Warning! Danger of Amputation!
The Mayco pump is equipped with a nitrogen accumulator,
which stores hydraulic energy. You will be required to put your
hand in the concrete cylinders or near the suttle. You are at
extreme risk if the engine is running or if pressure is in the
hydraulic system. Prior to working on the pump, stop the engine
by turning off the ignition switch, remove starter key, place a “Do
not operate” tag over the switch and disconnect the battery. The
pressure reading on the accumulator pressure gauge must read
zero. Always relieve the accumulator circuit to zero pressure
prior to working on the pump.
Replacement procedure
Step 1: Remove and plug the two hydraulic hoses connected
to the remix motor. P/N 25425.
Step 2: Remove the hopper discharge nipple P/N 25836 and
loosen sleeve seal P/N 16819 inspect and replace if
wear is excessive.
Step 3: Remove the two tie rod nuts P/N 16166 and the four
eyebolt nuts P/N 452558.
Step 4: With lifting device; remove hopper P/N 25174 use
extreme care not to damage the hopper seal P/N 16184.
Step 5: Start engine and turn on pressure test switch, cycle
pump in reverse until hydraulic system obtains
maximum pressure, at this point turn pump and engine
off. Remove ignition key and disconnect battery. Think
safety! Check the hydraulic gauges on panel and make
sure accumulator pressure reads zero. The one piston
should be in the fully discharge position at the end of
the concrete cylinder.
Step 6: At this time remove the three 3/8 – 16 x 3” bolts P/N
492388 from the piston. Remove the front faceplate P/
N 16464.
Step 7: Next, install two the 3/8’ 16x3” bolts P/N 492388 back
into the piston – do not tighten. Use the two bolts as
leverage to remove the rubber piston cup and rear
components.
Step 8: Reassemble – obtain two 3/8 16x7” full thread studs
(these studs will be used to assist in assembly
alignment) insert the two studs into the piston adapter
P/N 16460. Coat the concrete cylinder with grease.
Step 9: The new “O” ring P/N 14407 must now be modified.
Using a sharp knife cut four oil passage grooves into
the ring. the grooves should be placed at a distance of
90
o apart. The cut should be a v-shaped design, 0.059”
deep and 0.157” wide at the top.
Step 10: Install “O” Ring P/N 14407 around oiler plate P/N
16461. Install plate into concrete cylinder utilizing the
studs for alignment.
Step 11: Install the felt holder P/N 16462 over the oiler plate.
Install felt ring P/N 16462 into felt holder. Note: felt ring
must be saturated with 30 wt. oil prior to installation.
Install bronze ring P/N 14408.
Step 12: Using silicon sealant place a small bead of sealant
material on the front of the rubber piston P/N 16463
and the rear of the face plate P/N 16464. Install over
alignment studs and into concrete cylinders.
Step 13: Insert one 3/8” 16x3” bolt P/N 492388 into the open
bolt hole, remove alignment studs one at a time and
install the remaining 3/8” 16x3” bolts.
Note: Before installing 3/8” bolt, coat the back of bolt heads with
silicon sealant. Torque all three bolts equal at 55 ft. lbs. each.