5 Operation
5.1 Stuffing box
Stuffing box with packing rings without quenching gland and grease lubricator.
Periodically inspect stuffing box to see that there is sufficient leakage to lubricate the packing and main-
tain a cool box. Never draw up packing so that the stuffing box heats, as this will cause damage to both
packing and shaft. Always draw up gland nuts evenly and only when pump is running.
After pump has been in operation for some time and the packing has been completely run in, at least 40
to 60 drops per minute of the liquid should be allowed to trickle from the stuffing box at all times for cool-
ing and lubricating the packing and shaft sleeve.
Stuffing box with packing rings with quenching glands.
The same precautions as described above apply. However, the amount of leakage through the packing
cannot be so readily ascertained, due to the quenching liquid. In most cases, the valve on the quenching
liquid supply line can be shut off for a short period and the amount of leakage determined . In no instance
should the gland be drawn up tight.
Stuffing box with packing rings with grease lubricator.
Operation is the same as directed in
, with the addition that the handle on the
lubricator should be given a tum or two about every 100 hours of operation.
5.2 Operating at reduced capacities
Do not operate a centrifugal pump at greatly reduced capacities or with discharge gate valve closed be-
cause the energy required to drive the pump is converted into heat. If this condition exists over a long
period, the temperature of the liquid in the pump may increase until the boiling point is reached. If this
occurs, the rotating parts are exposed to vapor with no lubrication and they may score or even seize to
the stationary parts; and furthermore, if running clearances have enlarged due to wear, seizure may not
take place. Continued operation under these conditions may create an explosive hazard due to the con-
fined vapor under high pressure and temperature.
To guard against possible damage, protective devices are available, such as:
1.
Liquid temperature relay or thermostat which will shut-off the unit if the liquid temperature in the
pump exceeds a predetermined maximum. This device guards against possible damage due to
running the pump against a closed valve.
2.
Constant open by-pass orifice between the pump discharge and any check or regulating valve in
the discharge line. The liquid through the orifice is returned to the suction source. The amount of
liquid by-passed is a function of input horsepower and the allowable temperature rise. This de-
vice also is insurance against damage due to running the pump against a closed discharge valve
or very low flow conditions.
3.
Bearing temperature relay which will shut the unit down if the bearing temperature exceeds a
predetermined maximum.
4.
Low suction pressure control which will shut off the unit should the suction pressure drop below a
pre-established minimum.
A centrifugal pump should never be throttled for capacity adjustment on the suction side.
5 Operation
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3655 Installation, Operation and Maintenance Instructions
