10-1
10. Special specification
10.1 Negative suction type
This section describes specification of the negative suction type
water supply unit.
By employing the negative suction type unit, suction of up to -4m
(actual pump head) and -6m (total pump head) is enabled.
A constant relief kit (an orifice, a ball valve, a nipple, and a union)
is provided. Connect a constant relief pipe to the kit to send water
back to the source of water supply.
Note
For the installation procedure of the constant relief pipe, there may be an
applicable guideline or guidance from local governments or other official
institutions. Carefully check for such guidelines and follow the instructions.
Note
A standard model can be modified to the negative suction type.
For further information, contact us.
[Instructions only applicable to negative suction type]
(1) Ensure to install the constant relief pipe
c
for each
pump.
(2) Submerge the end of the constant relief pipe deep
enough to prevent exposure to air even if refilling of
water creates waves on the surface. In addition,
keep a distance from the suction pipe so that air
from the constant relief pipe does not enter the
suction pipe.
(3) Fully open the valve
d
during operation. (Water
flows at a rate of about 10 L/min.)
(4) Ensure to install the suction pipe
e
for each pump,
and provide a rising slope (at least 1/100 degrees)
leading up to each pump to prevent the formation of
air pockets inside the pipe. Furthermore, install
joints in a way that no air enters from there.
Pay special attention because the flow rate of the
subsequently activated pump exceeds the value
devided the maximum water usage by the maximun
number of paralleled units.
(5) Ensure to attach a foot valve
f
with a strainer to the
end of the suction pipe
e
to block entrance of
foreign matter or objects. The suction port must be
located at a position more than twice as deep as the
size of the suction pipe diameter (D) below the
lowest water level, and at a distance of at least 1 to
1.5 times the pipe diameter (D) away from the bottom and the side of the water tank.
(6) Do not attach a sluice valve to the suction pipe
e
.
(7) Install strong piping supports
g
to prevent the weight of the piping components from being applied to the
unit.
Fig. 10-1(a) Constant relief kit
Orifice
Nipple
Suction flange
Union
3
5
4
1
Lowest level
1 to 1.5D or more
300mm or more
2D or
m
o
re
1 t
o
1.
5D
or m
o
re
D
100
1
2
Fig.10-1(b) Piping installation example
