Goulds Pumps 3500XD - IOM - Manual (Page 28)

DILUTION SYSTEM – TYPICAL
(Refer to Figure 16A and 16B)
For Order Specific Description - Refer to the IOM Appendix
An automatic standpipe dilution system is recommended so
the highest possible average consistency for which the
discharge piping is designed can be continuously delivered
by the pump. The consistency of the stock being pumped is
the major contributor to friction head loss in the discharge
piping, followed by temperature and pH (this is true only if
the same fiber type is being pumped). The higher the
consistency, the greater the friction head loss will be.
Usually the only parameter or variable that can be adjusted
in the standpipe is stock consistency, which can be
controlled by the dilution system.
The dilution system normally consists of an upper spray
nozzle with a control valve (DCV-1) and a lower dilution
header with a control valve (DCV-2)
In the auto mode, the upper dilution valve (DCV-1) will
open to assist pumping when the standpipe level exceeds its
set point by 10%. A maximum signal selector is also used
to allow DCV-1 and DCV-2 to be open a preset amount,
while still maintaining the automatic function on an
increase in level.
The normal set point of the standpipe level controller (LCI)
is approximately 25%. When the level exceeds 25%, the
level control valve opens to bring the level back to its
set-point. When the level exceeds 35%, the dilution
controller (DCI) will signal the dilution valve (DCV-1) to
start to open. It will open gradually with level and be
100% open at 85% level. DCV-1 will gradually close as
the level decreases back to its set-point.
The lower dilution valve (DCV-2) should be programmed
to begin opening when DCV-1 is greater than 50% open,
and should be 100% open, when DCV-1 is 100% open.
Refer to the IOM Appendix for the order specific
information on the dilution scheme.
If the Model 3500XD is running and the standpipe level is
less than 10%, the upper and lower dilution valves will
open 100%. The valves will close when one of the above
conditions change.
SEAL/VACUUM FLUSH
(Refer to Figure 17A and 17B)
Seal and flush water is manually controlled with a
Safematic seal water monitoring unit. The seal water flow
to the bearing frame cooling coil and then to the
mechanical seal is monitored with a 0-2 GPM flow meter
and alarm. The seal water from the mechanical seal outlet
is directed to the gland flush connection or stuffing box
flush connection. Seal water required is 1-1½ GPM. A
second 0-2 GPM flow meter is supplied to provide 1-2
GPM directly to the Model 3500XD vacuum chamber. A
third flow meter (0-4 GPM) with alarm provides
approximately 2 GPM of make-up water directly to the
vacuum pump (Fig. 17A).
Check valves are provided to prevent stock from flowing
back into the seal and flush water control unit.
The water supply to the seal and flush water monitoring
equipment should be clean filtered water with a maximum
particle size of 50 microns, a maximum temperature of
100° F (40° C) and supplied at minimum pressure of 50
PSIG (3.5 bar). The seal water flow indicators for the
mechanical seal and the vacuum pump are equipped with
flow switches, which are set to give an alarm if the flow
falls below 50% of the set point. The Model 3500XD
pump will not start unless the seal water flow is above the
minimum.
For design pulp consistencies at 10% and lower it is not
neccessary to utilize a vacuum pump with the Model
3500XD. In this situation only two seal flush water flow
meters are required. The flow meter servicing the vacuum
pump is not required (Fig. 17B).
l
! CAUTION
Never operate the pump without liquid supplied to
mechanical seal. Running a mechanical seal dry, even
for a few seconds, can cause seal damage and must be
avoided. Physical injury can occur if mechanical seal
fails.
24
3500XD IOM 8/07