12/21/12
7
Fairbanks Nijhuis™
1500 and 2500 Series Single Stage End Suction Pumps
Installation, Operation & Maintenance
MODELS 1500 AND 2500
OPERATION INSTRUCTIONS
Centrifugal pumps operate under a wide range of conditions. The pump you have selected exactly fits your specific
requirements. Before putting your pump into operation, however, there are certain basic ground rules that must be
followed to assure maximum efficiency, long pump life, and maintenance-free service.
Centrifugal pumps should never be started or run dry. Operating a pump dry can cause burning of the packings or
seal, resulting in destruction of the packings or seals, and possible scoring of the pump shaft. To prevent the pump
from being run dry, the pump should be primed before starting it.
A centrifugal pump should not be throttled, or the volume controlled on the suction side of the pump. Throttling the
pump on the suction side not only reduces the capacity, but also reduces pump efficiency and, more importantly,
can cause serious damage to the pump due to cavitation. Cavitation occurs when the pressure at any point inside
the pump drops below the vapor pressure of the liquid. The liquid flashes and forms vapor bubbles. These bubbles
move along with the liquid into a higher pressure area, where the bubbles collapse or implode, creating an area of
low pressure. The implosion phenomenon is characterized by a crackling noise and sometimes by loud knocking as
the vapor bubbles are collapsed. Repetition of this action causes a wearing away of the metal on the impeller and
other parts of the pump, and if allowed to continue can result in serious damage to the pump.
Pump capacity can be effectively controlled by use of a throttling valve in the discharge piping. Most centrifugal
pumps can be operated for brief periods of time with the throttling valve closed without building up excessive
pressure or overloading the drive unit. In fact, a centrifugal pump operating against a closed discharge line at its
rated capacity actually requires less power to operate than it does when the throttling valve is open.
The pump should never be started with the throttling valve completely closed, however, because a condition of
water hammer could exist. The condition of water hammer is caused by an increase in pressure due to changes in
velocity of the liquid flowing through the pipe line. When the velocity is changed by closing a valve or by some other
means, the magnitude of the pressure produced is frequently much greater than the static pressure on the line, and
may cause rupture or damage to the pump, piping, or fittings. Water hammer may be controlled by regulating valve
closure or by the use of relief valves and slow-closing check valves.
On pumps equipped with packings, there should be sufficient leakage from the packing to ensure lubrication of the
packing and effective cooling of the stuffing box. The packing glands should always be adjusted evenly and not too
tightly. Overtightening the packing can generate heat which will burn the packing and cause scoring of the shaft,
making it necessary to replace both the shaft and the packings.
Adequate precautions should be taken to prevent freezing of liquid in the pump when the pump is not in operation.
If there is any possibility of freezing, the water should be drained off by removal of the plugs provided in the pump
casing.
All mounting bolts and piping connections must be firmly tightened to prevent excessive vibration, leakage, and
possible damage to the pump. The mounting bolts are particularly important. If they are not firmly tightened, the
base plate upon which the pump is mounted may deflect, causing a misalignment of the pump and the driver.
STARTING THE PUMP:
In order to start your pump, it will first be necessary to prime it.
