Track changers: the small part that decides whether the system runs unattended

A small part with a large failure mode

A track changer, or diverter, is the point where a train leaves one route and joins another. Physically it is a short movable section of rail that swings or slides between two settled positions, with a train running across it.

There are only two acceptable states. Fully in one position, or fully in the other. Anywhere in between is a gap in the rail with a loaded train coming towards it.

That is why this part gets more attention from us than its size suggests. Almost everything else in a transport system fails slowly and visibly. A changer that does not complete its travel fails suddenly, and what it damages is carriers, bobbins, and sometimes the track itself.

How ours are driven

We use electric linear actuators. The moving section is driven positively to each end of its travel and held there mechanically. It does not float, and it does not depend on pressure being maintained in order to stay where it was put.

Both end positions are sensed. The control system does not assume the changer has moved just because it was told to move. It waits to be told that the section has arrived and locked. Until that confirmation arrives, trains are not released through that point. If it never arrives, the system holds the traffic and raises an alarm instead of letting a train run onto a half-set rail.

That sequence is the whole idea. Drive it positively, confirm the position, release the train only then. It is not a complicated principle. It just has to be built in from the start, because it cannot be added convincingly afterwards.

What this is being compared against

Many track changers in this market are air operated, with a pneumatic cylinder pushing the section across.

Air works well when everything about the air supply is right. The difficulty is that in a spinning mill, everything about the air supply is frequently not right. Line pressure drops when other equipment draws on it. Fittings develop slow leaks. Cotton dust gets into the air preparation. Seals wear.

When any of that happens the cylinder does not fail cleanly. It moves slowly, or it travels part of the way and stops. The section ends up between positions, which is exactly the state that must never occur. And unless somebody has added position sensing, nothing in the system knows about it.

The result is a family of breakdowns that will be familiar to anyone who has run one of these systems. Jams at junctions, damaged carriers, derailments, and a maintenance routine built around hunting leaks and changing seals.

An electric actuator takes the air line, the air preparation and the leak hunting out of that part of the system completely. There is less to go wrong, and when something does go wrong the system finds out before a train does.

What it is worth to you

Two things, mainly.

The first is unattended running. A system that verifies its own route points can be left to run. A system that assumes them needs somebody watching for the failures it cannot detect by itself.

The second is maintenance load. Junction faults are a large share of the service calls on overhead transport systems. Removing a common cause of them takes a recurring job off your maintenance team.

We are happy to show you the arrangement properly on a site visit, including at a running installation. It is much easier to understand standing underneath one than reading about it.

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