Tie rod designs
Rubber expansion joints exert force on the adjacent sliding or fixed point when under pressure (active bellows cross-section surface area x operating pressure). These can be eliminated by using lateral or angular expansion joints with tie rods, such that the bearings are unburdened accordingly.
| Tie rods: | Several threaded rods mounted around the circumference assimilate pressure from the active bellows cross-section. Pipe flanges need to be parallel aligned for lateral expansion joints. |
| Pressure: | The tie rods assimilate the axial stresses of the expansion joint. |
| Stiffness rate: | Movements give rise to forces that rise under pressure and need to be taken into account in dimensioning the pipeline. Lateral stiffness rates to move the expansion joint under pressure can be found in the technical appendix; you may also enquire directly with us. |
The following tie rod designs are used depending on the requirements:
Design: B
Tie rods mounted outside in rubber bushing to accommodate reaction forces in the event of pressure (up to NB 300)
Design: R
Control unit plates: Tie rods mounted outside in the rubber bushing to accommodate reaction forces in the event of pressure (up to NB 300)
Design: E
Tie rods mounted outside in spherical bearings and ball disks to accommodate the reaction forces in the event of pressure
Design: K
Control unit plates: Tie rods mounted outside in spherical bearings and ball disks to accommodate the reaction forces in the event of pressure
Design: C
Tie rods mounted outside in rubber bushing and inside in the thrust limiter to accommodate stresses in the event of pressure and vacuum (up to NB 300)
Design: L
Control unit plates: Tie rods mounted outside and inside in spherical bearings and ball disks to accommodate the reaction forces in the event of pressure and vacuum
Design: M
Tie rods mounted outside and inside in spherical bearings and ball disks to accommodate the reaction forces in the event of pressure and vacuum
Design: F
Hinge tie rod: For angular movements on one level with plates and bolts to accommodate the reaction forces in the event of pressure and vacuum. Axis of rotation in the middle of the installation gap
Design: S
Tie rods mounted outside in spherical bearings and ball disks, as well as internally in thrust limiters to accommodate stresses in the event of pressure and vacuum
Design: G
Cardan joint tie rod: For angular movements on two levels with plates and bolts to accommodate the stresses in the event of pressure and vacuum. Axes of rotation in the middle of the installation gap
| Design: | Dimensioning according to design pressure (test pressure) based on the Pressure Equipment Directive |
| Pipeline: | For laterally stayed expansion joints the flange diameter of the pipeline must not be bigger than as defined in the norm, as otherwise the tie rod touches against the side of the flange and the lateral movement is restricted. |
| Materials: | Carbon steel in strength class 8.8 or stainless steel |
| Coating: | Spherical bearings and ball disks PTFE-coated Tie rods galvanised or hot-dip galvanised |
