Order Of Assembly; Precision Crankpin (Crankthrow) Bearings; Oil Scoop; Wiper Box Assembly - Pentair Myers Aplex Series Installation And Service Manual

(d) Fail ure to oil pin O.D. and crosshead bores, to
prevent galling. Use clean motor oil.
After in stalling the pin, carefully check the crosshead
O.D. to see if it is out-of-round. If so, a smart blow with
a rubber mal let will restore the crosshead O.D. into its
origi nal round ness.
ORDER OF ASSEM BLY
The connecting rod/crosshead assembly is installed
after the assembly of the crankshaft. In these models,
the rod and crosshead will pass through the wiper box
wall bore. With the frame in the horizontal position,
load the rods through the cradle.
PRECISION CRANK PIN
(CRANKTHROW) BEARINGS
Myers Aplex Series pump crankpin bearings require
no shimming to establish correct running clearance.
Precise machining of the con necting rod, caps and
crankp in journals is neces sary to achieve
this conve nience.
New Crankpin O.D.: 4.000/3.999
New Connecting Rod Bore: 4.232/4.233
Crankpins that are worn out-of-round, tapered, or
badly scored should either be dis carded or perhaps
salvaged by grinding under size, hard chrome-plated,
and finish ground to above diameter. (Myers Aplex
Series does not offer this service.)
Connecting rod /cap bore must be perfectly round and
with in above sizes and free of taper. Discard if elliptical
or tapered as the result of abnormal heat ing. Each cap
and rod is match-marked for correct identification.
Take care that each cap is reinstalled prop erly with its
companion rod. Bearing halves are identical and are
pre vented from rotating by tongues which fit into slots
in the cap.
Check that all oil holes are clean and fully open. Grit
is the greatest enemy of bear ings, however precisely
manu factured. Hence, all sur faces must be perfectly
clean and lightly oiled prior to assembly. Re move
any burrs or sharp cor ners which pre vent the per-
fect fitting of these precision bearings. Using a torque
wrench, tighten cap bolts as follows:
Thread Size: 1/2" – 13UNC
Tightening Torque: 60-75 Ft. Lb.
Specified torque, applied to clean, well oiled threads
and bearing faces, will create tensile stresses in the
cap bolts from 90,000 to 110,000 psi, approx. and will
provide correct initial tension. Myers Aplex Series
pumps use high strength cap bolts suitable for these
initial loadings, maintained by hardened spring
lockwashers. MA-120M use hardened lock washers
and other models use safety wire to maintain the
required tightness.
After all rods and caps are secured, slowly turn the
crank shaft to be sure no bearing is in a bind.
Using a flashlight, examine the location of each
connecting rod (eye end) within its crosshead. Rods
must not touch any crosshead boss or skirt.

OIL SCOOP

MA-120M also employ oil scoops which are cast
integrally with the power frame and are machined to
lightly contact the crankshaft cheek. No adjustment
is required.

WIPER BOX ASSEMBLY

GENERAL

Extension rod wiper boxes (sometimes referred to
as the diaphragm stuffing box, or stripper housing
assembly) serve two important functions: retention of
crankcase oil in the power end and exclu sion of dirt
and water.
Myers Aplex Series has developed a unique sealing set
which operates on a hardened and ground stainless
steel extension rod (often called "pony" rod), and a
steel baffle disc affording protection against leaking
plunger packing. The seals require no adjustment, only
correct and careful assembly.

"POLY PAK" SEAL

This seal keeps oil from leaking out of the power
frame. Developed by the Parker Seal Group, this
patented rod seal employs a soft nitrile rubber O-ring
to energize a special hard polyurethane Molythane
shell by forcing the inner lip against the rod and the
outer lip against the housing bore, as shown.
The Poly Pak seal is inserted into its counter bore with
its lips directed toward the oil in the crankcase. (Will
not work if installed backward!)

MECHANICAL OIL SEAL

The oil seal is to keep contamination out of the power
frame. With the box positioned in a hydraulic press,
install the backup seal against the Poly Pak seal, with
the lips of both seals facing downward.
The mechanical seal contains a garter spring. Check
to see that this spring is still properly located and in
its position. The mechanical seal has a metal case
which serves to force the Poly Pak seal into its cavity,
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