EBARA EFQU4 - Manual (Page 9)

EBARA Fluid Handling 8
VELOCITY (FT. /SEC.)= QUANT. (G.P.M)x.321 OR G.P.M. x 4085
AREA D²
VELOCITY (M./SEC.)= FLOW (M./MIN)x21.22 OR FLOW (M³/SEC.)
DIAMETER IN MM² AREA IN M²
Figure 2. Recommended Minimum Suction Line Submergence vs. Velocity
If it is necessary to position inflow close to the suction
inlet, install a baffle between the inflow and the in
suction lines, it must be the rigid-wall, reinforced type
to prevent collapse under suction. Using piping
couplings in suction lines is not recommended.
Suction inlet at a distance 1 ½ times the diameter of
the suction pipe. The baffle will allow entrained air to
escape from the liquid before it is drawn into the
suction inlet.
If two suction lines are installed in a single sump, the
flow paths may interact, reducing the efficiency of one
or both pumps. To avoid this, position the suction
inlets so that they are separated by a distance equal
to at least 3 times the diameter of the suction pipe. Suction Line Positioning
The depth of submergence of the suction line is
critical to efficient pump operation. Figure 2 shows
Recommended minimum submergence vs. velocity.
NOTE
The pipe submergence required may be reduced
by installing a standard pipe increaser fitting at
the end of the suction line. The larger opening
size will reduce the inlet velocity. Calculate the
required submergence using the following
formula based on the increased opening size
(area or diameter).
DISCHARGE LINES
Siphoning
Do not terminate the discharge line at a level lower
than of the liquid being pumped unless a siphon
breaker is used in the line. Otherwise, a siphoning
action causing damage to the pump could result.
Valves
If a throttling valve is desired in the discharge line,
use a valve as large as the largest pipe to minimize
friction losses. Never install a throttling valve in a
suction line.
With high discharge heads, it is recommended that a
throttling valve and a system check valve be installed
in the discharge line to protect the pump from
excessive shock pressure and reverse rotation when
it is stopped.