Bypass Piping; Lubrication; V-Belt Drive - Pentair Myers Aplex Series Installation And Service Manual

Locate the relief valve and pressure gauge ahead of
any block valve and so that the pressure in the pump
is always reflected at the relief valve. The relieving
capacity of the relief valve must exceed the capacity of
the pump to avoid excessive pressure while relieving.
Use a full size relief line.
To minimize vibration (whether hydraulic or mechanical),
discharge lines should be kept short, direct, well
supported and solidly anchored. Avoid "dead" ends and
abrupt direction changes.

BYPASS PIPING

Some designers ignore this important aspect of proper
design of pump piping systems.
A reciprocating pump, especially after maintenance of
the valves or plungers, starts with one or more fluid
chambers full of air. Pumps operating on propane,
butane, or other volatile liquids start with vapor in the
fluid chamber(s).
Positive displacement pumps do not automatically purge
themselves of air and gas after shutdown. For example,
a quintuplex plunger pump will, after servicing, expel
the air in four of the five pump chambers. Thus, the
pressure from four of the "active" cylinders will keep
shut the discharge valve of the "inactive", or "air bound,"
cylinder. Then, the air or gas in this cylinder will be
compressed and expanded by its reciprocating plunger
and never leave the chamber. Similar effects occur in
duplex and tri plex pum ps.
To overcome these difficulties, adequate provision for
expel ling the gas in the "air bound" cylinders must be
present. Common practice is to totally relieve the pump
of all dis charge pressure during the start-up, after
servicing.
Consider the operational advantage of a full-sized
bypass line (return to tank) which substantially removes
discharge pressure from all cylinders during the start.
This requires a block valve on the discharge side and a
full opening bypass valve on the other side.
For economy, the bypass (to tank) can be combined
with the relief valve discharge line. This line must be
full-sized, well supported, and sloped downward to
avoid freezing in cold weather. (A frozen relief valve line
provides no protection to either the pump or operating
personnel!)
The ability of a reciprocating pump to be "self-priming"
depends on the ratio of the swept (displaced) volume in
the cylinder to the unswept (clearance) volume at the
end of the stroke. This depends on the design of the
fluid end and on the plunger size selected.
Choice of the largest size plunger for a particular fluid
end improves this compression ratio and so leads to
"self priming", or easy priming. Choice of the minimum
size plunger sometimes leads to difficulties, especially
with pumps that require frequent servicing, or which
handle volatile liquids, or which contain substantial
amounts of dissolved air or gas. An automatic bypass
and purging system for these applications may be
merited.

LUBRICATION

Pumps are shipped without oil from the factory. If the
pump is fitted with a planetary gear reducer, it must be
filled separately through its own fill port. Gear reducers
should be filled to approximately the halfway point.
Myers Aplex Series pumps use S.A.E. 40 wt.
nondetergent oil in the crank case. This oil requires only
a nonfoaming additive and should possess good water
separation (antiemulsion) character is tics. Such oils are
often labeled "industrial" or "turbine" quality lubricants.
If these oils are not available, a good quality gear oil or
EP oil may be substituted. See lubrication guidelines.
In temperate climates, oil viscosity selected should
fall between 70 and 84 seconds Saybolt viscosimeter at
210º F. In arctic service, low pour point oils
are needed.
After the first 500 hours of operation in a new pump,
drain the oil. Refill with clean, fresh oil. Thereafter,
change the oil every 1,500 hours or sooner if it becomes
contaminated with water or dirt. Fill to the center of the
sight gauge. Recheck after start ing, adding oil to center
of gauge while running.
The table below shows the quarts of oil needed for each
pump.
Quarts of Oil
15
MA-95L
MA-120L
MA-120L-HD
SC-170L

V-BELT DRIVE

A properly designed, well-aligned V-belt will provide
years of reliable, economical service if properly
tensioned and kept dry, free of oil and ventilated.
Alignment is critical for long life. If the shaft axes
are not truly parallel, or if the sheave grooves are not
positioned in good alignment, some belts will carry most
of the load, resulting in their disproportionate load share
and may actually twist or turn over in the groove. Use
a straight edge across the rim of the sheaves to detect
and correct for misalignment.
17
18
MA-95M
MA-120M
SC-170
SC-170H
SC-170DD