Description of a sudden blocking scenario
The kinetic energy of the rotor has to be absorbed by the installation if the pump blocks suddenly. The
maximum resulting loads have been measured on a test bench by simulating the worst-case turbo
pump blockage with a rotor split in two with the pump rotating at nominal speed. The impact on the rotor
parts creates the following transient loads.
Axial force (A)
The rotor parts can be ejected out of the pump inlet flange and can hit the valve plate or any other part
of the system. If this is placed close to the turbo pump and if it has high stiffness, the impact can create
a high axial force on the installation. Such axial force has not been observed on a standard pendulum
valve, or when there is a free space greater than 100 mm.
Bending moment (B)
The impact of the rotor parts on the housing will create a radial force on the housing. This radial force
will create a bending moment on the system as a function of the distance to the pump. The deceleration
of the rotor parts creates a torque value on the pump housing, which is transmitted to the equipment.
Torque (C)
The deceleration of the rotor parts creates a torque value on the pump housing, which is transmitted to
the system. The maximum values of the axial force and the bending moment occur at approximately the
same time. A delay of up to several ms has been observed for the maximum torque value.
B
C
C
A
1
2
10
9
8
7
6
5
4
3
2
1
0
20
40
60
80
100
120
0
0
0.5
1
1.5
2
2.5
C
B
A
Axi
a
l
fo
rce
-
kN
T
o
rq
u
e
–
Be
n
d
in
g
mo
me
n
t
kN
·m
Time ms
Fig. 5:
Graph of the loads exerted on the equipment
1 Turbopump
2
Pendulum valve
Technical data
Unit
Set Point
Nominal speed
min
-1
50000
Energy
kN·m
24
Torque
(C)
Max. kN·m
9
Duration ms
1
Delay ms
1
Bending moment
(B)
Max. kN·m
6
Duration ms
0.5
Delay ms
0
Axial force
(A)
1)
Max. kN
0 to 110
Duration ms
0.3
Delay ms
0
1) Maximum axial force occurs when pump inlet is blocked by the rigid parts. There is no load on the
equipment in case of limited stiffness, e.g. with a valve.
Tbl. 1:
Loads exerted on the equipment
Installation
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