EBARA EFQT3 - Manual (Page 9)

EBARA Fluid Handling 9
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.