Grundfos CR 95 Data Booklet page 16

4
Thrust handling device
Fig. 12 Thrust handling device
A thrust handling device (THD) is factory-fitted on
pumps with 100 Hp (75 kW) motors or larger. The
system consists of two parts. A rotating part mounted
on the shaft end below the first impeller as well as a
non-rotating part mounted in or on the pump base.
The THD absorbs the main part of the thrust force
generated by the impellers and thereby reduces the
resulting axial force the motor bearings must absorb.
This enables the use of standard ball bearings in the
motor instead of special angular contact ball bearings.
Note: For applications involving CIP
(cleaning-in-place) and motors above 75 Hp (55 kW),
use a bearing flange and a base without THD.
Fig. 13 Position numbers for THD parts
Pos. Description
120a Thrust disc
120b Rotating ring
120g Stationary ring
120h Lifting plate
- O-rings
* On request for CRN.
Operating pressure and inlet pressure
Do not exceed the limit values for these pressures:
• maximum operating pressure
• maximum inlet pressure.
16
Minimum inlet pressure, NPSH
We recommend that you calculate the inlet pressure
"H" in these situations:
• The liquid temperature is high.
• The flow rate is significantly higher than the rated
• Water is drawn from depths.
• Water is drawn through long pipes.
• Inlet conditions are poor.
To avoid cavitation, make sure that there is a minimum
pressure on the inlet side of the pump.
Calculate the maximum suction lift "H" in m head as
follows:
H = p
p
NPSH
H
H
If the calculated "H" is positive, the pump can operate
at a suction lift of maximum "H" ft (m) head.
If the calculated "H" is negative, an inlet pressure of
minimum "H" ft (m) head is required.
120a
120b
120g
120h
Material
Stainless steel
Silicon carbide
Silicon carbide*
Tungsten carbide
Stainless steel
EPDM
FKM
Note: To avoid cavitation, do not select a pump with a
duty point too far to the right on the NPSH curve.
Always check the NPSH value of the pump at the
highest possible flow rate.
flow rate.
x 10.2 - NPSH - H - H
b f
Barometric pressure in ft (bar).
Barometric pressure can be set to 39.9 ft (1 bar).
=
b
In closed systems, p indicates the system pressure in
b
feet (bar).
Net Positive Suction Head in ft (m) head, to be read from
= the NPSH curve at the highest flow the pump will be
delivering.
Friction loss in inlet pipe in ft (m) head at the highest
=
f
flow the pump will be delivering.
Vapor pressure in ft (m) head, to be read from the vapor
=
v
pressure scale. H depends on the liquid temperature t
v
H
f
H p
b
NPSH
H
v
Fig. 14 Minimum inlet pressure, NPSH
CR, CRN 95-155
v
.
m
tm Hv tm Hv
(°F) (Ft) (°C) (m)
370 413 190 126
360 328 180 100
340 259 170 79
160 62
320 203
300 150
148 45
40
131
280 115 140 35
98 30
130
270
82 25
250 120
66 20
49 15
230 110
39 12
212 100
33 10
26 8,0
90
194
20 6,0
16 5,0
176 80
13 4,0
158 70
10 3,0
60
140 6.6 2,0
4.9 1,5
122 50
3.3 1,0
2.6 0,8
104 40
2.0 0,6
86 30
1.3 0,4
0.9 0,3
20
68
0.7 0,2
50 10
0.3 0,1
32 0