Diaphragm Pump System; Operation; Mechanical Seal; Liquid Temperature And Overheating - Generac Power Systems MAGNUM Owner's Manual

Diaphragm Pump System

Some pumps are equipped with a diaphragm system. The
system is a fully automatic self-priming, dry-prime vacuum
pump. It can rapidly prime and re-prime completely
unattended. The pump utilizes a diaphragm, which creates
vacuum on the suction side of the pump, causing air to be
displaced by water moving up the suction pipe. The water
approaches the ball valve and forces the ball valve closed,
shutting off the air flow diaphragm pump. The pump is then
primed and operating at full flow.
NOTE: The diaphragm vacuum pump system also
comes with run-dry capability, which allows indefinite dry
running of the seal.

Operation

Priming time is a function of the volume of air in the suction
line and the RPM of the vacuum pump. High lifts and larger
suction line diameters will require longer priming times. If
the pump will not prime or maintain prime, or if the vacuum
pump runs hot or passes water, refer to Troubleshooting.
IMPORTANT NOTE: Do not attempt to reduce the
priming time by operating the pump at speeds
exceeding recommendations. Doing so will shorten
the life of the vacuum pump.
When pumping in extremely cold conditions, ice may form
on the prime valve seat or linkage, preventing closure and
allowing water into the vacuum pump. Close observation
must be maintained and the pump shut down at the first
signs of excessive water coming from the vacuum pump.
Should the discharge check valve become plugged, the
pump must be shut down and the valve cleaned out. Refer
to Discharge Check Valve. Clogging of the suction
strainer or hose may result in loss of prime without recovery.
A vacuum gauge can be connected to the tap on the side
of the priming chamber to aid in diagnosing such clogs.

Mechanical Seal

The pump is equipped with a run-dry feature. The run-dry
feature employs an auxiliary gland and reservoir mounted
to the backplate. The rotation of the drive shaft circulates
oil from the reservoir to the gland, then back to the reservoir.
The oil serves to cool the seal faces even when there is
no liquid in the pump casing. A V-ring may be installed
when space allows.
With the backup run-dry feature, the pump can operate for
a short period of time with no liquid in the pump casing
without causing damage to the mechanical seal. The run-
dry option is not intended for extended periods of operation
without liquid in the pump casing, but rather as a safety
feature to save the mechanical seal should the pump
unexpectedly lose prime or inadvertently be started without
being primed.
Recommended reservoir oil:
Owner's Manual for Dry-Prime Diesel Trash Pumps
• Chevron Turbine Oil GST32 or other ISO viscosity
grade 32 or below (synthetic oil recommended)
• Transmission fluid or hydraulic oil
The reservoir oil should be a non-volatile substance that
is compatible with the mechanical seal elastomers, will not
cause rusting, and will not freeze in cold climates. Refer
to Wear Rings for more information.
CAUTION
Equipment Damage. Always run pump with water
in the priming chamber. Failure to do so will result
in equipment damage and/or failure.

Liquid Temperature and Overheating

The maximum liquid temperature for this pump is 160 ºF
(71 ºC). Do not apply it at a higher operating temperature.
Overheating can occur if the pump is operated with the
valves in the suction and/or discharge lines closed.
Operating against closed valves could bring the liquid to a
boil, build pressure, and cause the pump to rupture or
explode. If overheating occurs, stop the pump and allow it
to cool before servicing it. Fill the pump casing with cool
liquid.
WARNING
Personal Injury. Do not operate pump with flow
completely restricted. Doing so could cause pump
casing to explode and could result in death or
serious injury.

Pump Vacuum Check

With the pump inoperative, install a vacuum gauge in the
system. Block the suction line and start the pump. At
operating speed, the pump should pull a vacuum of 20 in.
(67.7 kPa) of mercury or more. If it does not, check for air
leaks at the suction piping gaskets.

Bearing Temperature Check

Bearings normally run at higher than ambient temperatures
because of heat generated by friction. Temperatures up to
160 ºF (71 ºC) are considered normal for bearings, and
they can operate safely to at least 180 ºF (82 ºC). Measure
the bearing temperature with a contact-type thermometer.

Stopping The Unit

Allow the engine to idle briefly before switching the Key
switch to the OFF position.
Operation
(000280)
(000273)
39