EBARA EFQT12 - 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 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.