Series 8100/8150/8200/9100 Fire Pump
23
AC6102 Rev 0
5
Fig. 17
Load and Moment orientation for Horizontal Split Case
fire pump casings
Notes:
1) F = External force (tension or compression (+/-))
2) M = External moment (clockwise or counter-
clockwise)
3)
∑F=√ F
x
2
+ F
y
2
+ F
z
2
, (∑F = resultant force).
4)
∑M=√ M
x
2
+ M
y
2
+ M
z
2
, (∑M = resultant moment).
5) The nozzle loads applied to the pump flanges
must not exceed the values given in the tables.
6) Values given are for loads applied concurrently in
+ or – direction. Individual forces and moments
can be increased provided that ∑F and ∑M are
not exceeded.
7.6.3
Suction piping
The sizing and installation of the suction piping is extremely
important. It must be selected and installed so that pressure
losses are minimized and sufficient liquid will flow into the
pump when started and operated. Many NPSH (Net Positive
Suction Head) problems can be directly attributed to improper
suction piping systems.
Suction piping should be short in length, as direct as
possible, and never smaller in diameter than the pump
suction opening.
A minimum of ten (10) pipe diameters between any elbow or
tee and the pump should be allowed. If a long suction pipe is
required, it should be one or two sizes larger than the suction
opening, depending on its length.
CAUTION
An elbow should not be used directly before
the suction of a double suction pump if its
plane is parallel to the pump shaft. This can
cause an excessive axial load or NPSH
problems in the pump due to an uneven flow
distribution. If there is no other choice, the
elbow should have straightening vanes to
help evenly distribute the flow.
Eccentric reducers should be limited to one pipe size
reduction each to avoid excessive turbulence and noise.
They should be of the conical type. Contour reducers are not
recommended. When operating on a suction lift, the suction
pipe should slope upward to the pump nozzle.
A horizontal suction line must have a gradual rise to the
pump. Any high point in the pipe can become filled with air
and prevent proper operation of the pump. When reducing
the piping to the suction opening diameter, use an eccentric
reducer with the eccentric side down to avoid air pockets.
NOTE:
When operating on suction lift never use a concentric
reducer in a horizontal suction line, as it tends to form an air
pocket in the top of the reducer and the pipe. Some correct
and incorrect suction piping arrangements are shown in Fig.
18.
When installing valves in the suction piping, observe the
following precautions: If the pump is operating under static
suction lift conditions, a foot valve may be installed in the
suction line to avoid the necessity of priming each time the
pump is started.
This valve should be of the flapper type, rather than the
multiple spring type, sized to avoid excessive friction in the
suction line. (Under all other conditions, a check valve, if
used, should be installed in the discharge line, see section
7.6.4 Discharge Piping).
When foot valves are used, or where there are other
possibilities of “water hammer,” close the discharge valve
slowly before shutting down the pump.
Where two or more pumps are connected to the same
suction line, install gate valves so that any pump can be
isolated from the line.
Gate valves should be installed on the suction side of all
pumps with a positive pressure for maintenance purposes.
Install gate valves with stems horizontal to avoid air pockets.
Содержание AC Fire Pump 8100 Series
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Страница 41: ...AC6102 Rev 05 40 Table 14 Troubleshooting List...
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