WK
Balancing Liquid Piping
1.
Field of Application
Balancing liquid piping is a must for WL pumps. However
for WK/WKS pumps balancing liquid piping is required
whenever the discharge pressure exceeds 20 bar for sizes
40 to 65 and for sizes 80 to 150 when this pressure
exceeds 15 bars.
2.
Requirement and Connection
In case of WK/WKS pumps, the balancing of major portion
of axial thrust is achieved by means of balancing liquid
holes provided on each stage impeller. With this, the
pressure equalization on either side of impeller is attained.
Due to this, a certain quantity of liquid being pumped flows
towards the pressure side, which ultimately enters the
balancing chamber, formed between the walls of stuffing
box housing and discharge casing. This balancing liquid
quantity has to be drawn off from the balancing chamber,
which otherwise will accumulate there only and hamper
the performance of the pump. For this purpose a pipe
line is provided, which connects this high pressure
chamber to the low pressure region of suction casing (fig.
A). By this the pressure relieving of the discharge side
stuffing box housing is also achieved.
In case of WL pumps, the balancing of major portion of
axial thrust is achieved by means of balancing device.
This also involves the flow of balancing liquid into the
balancing chamber, which again has to be drawn off. In
case of WL pumps, this piping is either connected back
to the suction casing (fig. A) or to the feed water tank (fig.
B) depending upon the temperature and differential head
of the pumping liquid.
3.
Size
The tapping size provided on the balancing chamber of
discharge casing and the recommended pipe line sizes
are given in the following table :
Pump Size
Tapping on
Pipeline size
Balancing Chamber
mm
40, 50, 65
R 3/8’’
16 x 1.5
80, 100
R 3/4’’
20 x 2
125, 150
R 1’’
25 x 2
4.
Accessories
Whenever the balancing liquid piping is connected back
to the suction casing, no accessories are required.
When this connection is given back to feed water tank
(fig. C) then the following accessories are necessary.
The sizes of the valves are to be considered as the
corresponding size of the pipeline given in article 3 above.
Pipe line size
Valve Size
Size of
Safety Valve
16 x 1.5
DN15
20 x 2
DN20
DN20 x 32
25 x 2
DN25
Accessory
Purpose
Pressure Rating
Pressure gauge
Indication of
0-6, 0-10 kg/cm2
balancing line
reading
pressure
Check Valve
Restrication of
PN 40
back flow of
balancing liquid
Globe Valve
Isolation of
PN 40
balancing piping
for the purpose
of maintenance
Safety Valve
To safe guard the
PN 40 x 10
balancing piping
Fig. A
Balancing piping
Balancing piping from balancing chamber to suction casing
Fig. B
Balancing liquid in the deareator
Balancing piping in the feed water tank.
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