TP40-160/2 Shaft Seals Manual

10
Shaft seals in general
Shaft seals
Calculation of the efficient closing force (F
C, eff.
):
Calculation of the efficient seat load (P
eff.
):
Calculation example, balanced shaft seal, Grundfos
type K
Data:
Calculation of the balancing K-factor:
Calculation of forces acting on the shaft seal:
Calculation of the closing force (F
C
):
Calculation of the opening force (F
O
):
Calculation of the efficient closing force (F
C, eff.
):
Calculation of the efficient seat load (P
eff.
):
Depending on the shaft diameter and the material of the
stationary seat, unbalanced shaft seals are suitable for
applications up to 25 bar. Balanced seals are suitable
for applications up to 80 bar by reducing the load of the
seal faces. To obtain this reduction, the shaft or bush
must have a recess, reducing the external and internal
diameter of the rotating seal face. The area affected by
the hydraulic pressure in the seal housing is thus
reduced without changing the area between the seal
faces.
The smaller load on the seal faces causes less gener-
ation of heat, and consequently less friction and
mechanical wear on the shaft seal. This improves the
cost of ownership of the shaft seal.
For balanced shaft seals, the following applies:
A 120 mm
2
B 150 mm
2
F
S
45 N
P0.8 N/mm
2
F
C, eff.
165 60–=
F
C, eff.
105 [N]=
P
eff.
105
150
----------
=
P
eff.
0.70= [N/mm
2
]
K
120
150
----------
=
K = 0.8
F
C
120 0.8×()45+=
F
C
141 [N]=
F
O
150
0.8
2
--------
⎝⎠
⎛⎞
×=
F
O
60 [N]=
F
C, eff.
141 60–=
F
C, eff.
81 [N]=
P
eff.
81
150
----------
=
P
eff.
0.54= [N/mm
2
]
K
A
B
--- -
1 –[]≤=