Teikoku USA | Chempump
Instruction Manual NC-Series 0220
14
2.4 Special Conditions & Features
2.4.1 Backflushing 32-S
For normal clear fluid applications, Chempump
TM
NC-Series are
cooled and lubricated by fluid being pumped through the system.
For slurry and other “dirty” applications, backflushing is recom-
mended. Backflushing is noted on the order when recommended.
See
for a typical back flush installation.
Pumps using backflush are normally supplied without circulat-
ing tubes. Clear fluid is brought to the fitting at the front of the
motor section by customer’s piping as shown in Figure 2-4. The
amount of clear base fluid introduced in this manner should ap-
proximate the standard flow rates listed in
Table 2-9. Recirculation Flow Rate
MODEL
RECIRCULATION
FLOW RATE
(GPM)
RECIRCULATION
FLOW RATE
(M3/HR)
NC-AA-6
2.5 - 4.5
0.57 - 1.0
NC-AA-8
3 - 6
0.68 - 1.36
NC-AB-6
3.5 - 4.5
0.79 - 1.0
NC-A50-8
5 - 7
1.14 - 1.59
NC-A60-8
5 - 7
1.14 - 1.59
NC-A05-10
7 - 9
1.59 - 2.04
NC-50-10
7 - 9
1.59 - 2.04
NC-A60-10
8 - 10
1.82 - 2.27
Backflush pressure should be suction pressure plus 20-30% of
the pressure developed by the pump. Excessive backflush pressure
will destroy the thrust balanced operation built into the NC-Series
by causing excessive forward thrust.
Procedure:
1. Remove the circulation tube and plug off the port in the dis-
charge neck of the pump casing. (This is done at the factory if
specified in the order).
Figure 2-4. Back-Flush System
2. Supply clear liquid to the port in the adapter normally used for
the circulating tube size.
3. If the back flushing liquid is hot, auxiliary cooling methods,
such as water jacketing the stator must be employed. The
temperature of the backflush fluid should not be close to its
boiling point and should not exceed 300˚ F.
2.4.2 Reverse Circulation 13-SE
For normal clear fluid applications, Chempump
TM
NC-Series are
cooled and lubricated by the fluid being pumped. However, when
the fluid being pumped is at or near its boiling point, the addi-
tional heat picked up from the motor combined with the recircu-
lation fluid returning to the low pressure at impeller suction may
cause vaporization inside the pump. In these cases the reverse
circulation method of lubricating the bearings and cooling the
motor should be used. Flow rates should duplicate those shown
in
.
In reverse circulation the cooling and lubricating fluid is forced
from behind the impeller into the motor section. It passes through
the front bearing, over the rotor, and across the rear bearing. The
fluid then exits the rear of the pump and is piped back to the suc-
tion vessel (not the suction line).
By this method, the fluid in the motor section is maintained at a
pressure close to discharge pressure. Flow through stator-rotor
cavity must be controlled to allow for good balance of pressure
and temperature without excessive flow.
Procedure:
1. Connect tubing (minimum 1/2") to the port provided in the
outboard bearing housing.
2. Run the tubing from the connection port fitting in the rear
back to the suction receiver, preferably above the liquid level.
3. Use large size suction line and gate valve for low pressure
drop and thus improve Available NPSH.
2.4.3 Internal Circulation 1-S
Internal Circulation is available on all NC-Series pumps. A unit
modified for internal circulation requires the elimination of the
circulation tube, fittings and discharge filter. Internal flow paths
are provided to direct the fluid circulation through the motor and
bearings.
NOTE:
Please contact the factory prior to any modification to in-
ternal circulation.
