Goulds Pumps AF (Axial Flow) (42"/1200mm/54/60"/66") LM/LMR Bearings - IOM" - Manual (Page 36)

36 AF (42-66) IOM
OPERATION
GENERAL CONSIDERATIONS
Service temperature in an ATEX classified
environment is limited by the table in the
ATEX identification section.
Do not operate pump below
minimum rated flows or with suction
and/or discharge valve closed.
These conditions may create an
explosive hazard due to vaporization
of pumpage and can quickly lead to
pump failure and physical injury.
Observe pump for vibration levels,
bearing temperature and excessive
noise. If normal levels are exceeded,
shut down and resolve.
Always operate the pump at or near
the rated conditions to prevent
damage resulting form cavitation or
recirculation.
Always vary capacity with regulating
valve in the discharge line. NEVER
throttle flow from the suction side.
Pump must never be throttled on
suction side.
NPSHa must always exceed NPSHr
as shown on Goulds performane
curves received with order.
Reference Hydraulic Institute for NPSH and pipe
friction values needed to evaluate suction piping.
Most axial flow pumps are in evaporator circulation
service and since the evaporator performance and the
amount of product depends on the rate of liquid
circulation, care should be taken to maintain these
pumps in good operating condition.
When production drops off, it is usually due to lower
circulation rate. An approximation of this rate can be
made by several methods:
• Temperature drop across the heat exchanger.
• Visual inspection of flow in evaporator body.
• Testing the circulating pump.
Items (1) and (2) above are covered by the evaporator
manufacturer.
While field conditions preclude absolute accuracy, a
check of pump performance will give reasonably close
results. This can be done by installing a mercury
manometer at pipe taps located at least-one pipe
diameter away from the suction and discharge flanges
of the pump. If-gauges are used, the pressure
differential times 2.31 divided by the specific gravity of
the slurry indicates the TDH against which the pump is
actually operating. If a manometer is used, then
inches of mercury times 1.0455 divided by specific
gravity equals TDH, providing water is in both legs of
the manometer and connecting lines.
Check the pump speed and determine flow rate (gpm)
from the pump curve. This curve will also give
efficiency from which the hp requirement can be
determined. A double check is to take motor ammeter
readings, convert to hp, figure 90% drive efficiency,
and use it against the pump curve to get GPM. This is
only an approximate check, as the hp curve on some
applications is rather flat, but is probably within 7-1/2%.
It is important to take and record these readings when
the equipment is new, so that later readings can be
judged on a relative basis.
OPERATING AT REDUCED CAPACITY
WARNING
DO NOT operate pump below minimum rated flows
or with a discharge valve closed. This condition
may create an explosive hazard due to
vaporization of pumpage and can quickly lead to
pump failure and physical injury.
Driver may overload if the pumpage
specific gravity (density) is greater
than originally assumed, or the rated
flow rate is exceeded.
!