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32 WILO SE 11/2023
7.1.2 Installation of a flange-end pump
Assembly of pumps with a combination flange PN 6/10
(Flange-end pumps DN 40 to DN 65 inclusive)
WARNING! Risk of personal injury and material damage!
The flange connection can be damaged and develop leaks if the pump is not
installed correctly. There is a risk of injury and material damage due to hot
fluid escaping.
• Never interconnect two combination flanges!
• Pumps with combination flanges are not permitted for operating pressures
PN 16.
• The use of securing elements (e.g. spring lock washers) can result in leakages
at the flange connection. They are therefore not permitted. The washers
supplied (Fig. 3, item 1) must be inserted between screw heads/nut heads
and the combination flange.
• The permissible tightening torques listed in the table below must not be
exceeded, even if screws of higher strength (
≥ 4.6) are used, since splinter-
ing may otherwise occur at the edges of the long holes. This may cause the
screws to lose their prestress and leakage can occur in the flange connection.
• Use screws of sufficient length. The screw thread must project by at least
one pitch of screw thread from the screw nut (Fig. 3, item 2).
• Install appropriate flat gaskets between pump and counter flanges.
• Tighten the flange bolts across diagonals in 2 steps to the prescribed tightening
torque (see Table 7.1.2).
• Step 1: 0.5 x permissible tightening torque
• Step 2: 1.0 x permissible tightening torque
• Check the flange connections for impermeability.
DN 40, 50, 65 Rated pressure PN 6 Rated pressure PN 10/16
Screw diameter M12 M16
Strength class ≥ 4.6 ≥ 4.6
Permitted tightening torque 40 Nm 95 Nm
Min. screw length for
• DN 40 55 mm 60 mm
• DN 50/DN 65 60 mm 65 mm
DN 80 Rated pressure PN 6 Rated pressure PN 10/16
Screw diameter M16 M16
Strength class ≥ 4.6 ≥ 4.6
Permitted tightening torque 95 Nm 95 Nm
Min. screw length for
• DN 80
70 mm 70 mm
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