Insulated adhesive joints
Today's signaling technology mainly makes use of track circuits, and the rails serve as conductors for them. At the borders of the individual block sections, the track circuit of the running rails is interrupted by means of an ISO-joint.
A high strength can be obtained with the multi-component adhesive for the bonding connections of the ISO-joints. The insulated joints previously produced consisted of wood and compressed wood fish plates. They were replaced by extremely sturdy steel fish plates. The different temperatures and the resulting gaps in the insulated joints caused a great deal of damage to the joints, and thus, a high level of maintenance costs. Photo: The yellow Skl1k clamps are easy to recognize. They are essential for the purpose of avoiding contact between fish plates and rail fastening parts.
A high strength will be achieved with the multi-component adhesive for the bonding connections of the ISO-joints. The insulated joints which was previously produced consisted of wood and compressed wood fish plates. They were replaced by extremely sturdy steel fish plates. The different temperatures and the resulting gaps in the insulated joints caused a great deal of damage to the joints and thus this also had a high level of maintenance costs.
Insulated adhesive joint IVB 30:
The special feature here is that the rail ends are obliquely cut (angle 30°) and abut with one another, so that the resulting force transfer between the two rail ends occurs gradually and the usual impact of the wheel (so-called wheel shock) no longer occurs in one step.
- Optimum force transmission by bonding of the entire joint.
- Trains gradually roll over the joint without Impact.
- Longer life.
- Reduced noise.
- Maintenance intervals are extended.
In order to achieve this angular cut-off angle of 30°, in the upper area of the rail (rail head and upper rail web) the track is diagonally sawn and the lower part (rail foot and half the lower rail web) straight at 90° angle to the longitudinal axis of the rail.
Inorder that the saw areas (sections) do not meet and result in damage to the saw blades, they are executed one after the other. In the middle section, a hole is drilled (used for destressing) in the front end.
This development is of enormous importance, for the railway track since the wheel impacts can appear as jolts in the track and lead to long term settlements and changes to the track geometry. The IVB30 can only be a fabricated joint.
The insulating adhesive joints S (Schmitz) and MT (Münch-Thermit):
They have proved to be very reliable. Both ISO types of joint differ primarily in the method of production and as a result, differ in the ways of force absorption or transmission. In the S-joint the transfer of forces from the rail ends to the fish plates passes through the adhesive force of the plastic adhesive and the bonded insulation rolls. With the MT-joint the forces from the rail ends are transmitted using the wedge effect of the screws into the fishing surface and further into the tensioned insulated fish plates. Due to the weather conditions the S-joint is no longer made in the track but only in the workshop. It is only tightened to 900 Nm and must harden for 24 hours.
Trains can run over the insulated MT joint after the first fastening down and retightening. However, no tensile stresses should be applied during hardening (along the rails). During a break of train operation the joint can be made, glued and put together. If the joint has been tightened with a torque of 1000 Nm it should be available to the signalling system in good order immediately and can be used by trains.
Because of its resistance to the weather, the MT-joint can also be installed in extended stoppages in the track. But it can also be prefabricated and then installed later with the rest of the rail units on location.
Passende Fachliteratur zur Bahninfrastruktur finden Sie hier:
The Basic Principles of Mechanised Track Maintenance
This book is dedicated to the many people involved in the day to day planning and performance of track maintenance activities. Providing a practical approach to everyday challenges in mechanised track maintenance, it is not just intended as a theoretical approach to the track system.
Railways aim at transporting people and freight safely, rapidly, regularly, comfortably and on time from one place to another. This book is directed to track infrastructure departments contributing to the above objective by ensuring the track infrastructure’s reliability, availability, maintainability and safety – denoted by the acronym RAMS. Regular, effective and affordable track maintenance enable RAMS to be achieved.