Data logging protects 13 tonne chain

Smartlink consists of a strain gauge linked to a microprocessor which collects data about the stresses and forces the chain is exposed to during the lowering and raising of the barrier.

Chain data logging technology from Renold is helping to protect the huge chain that is deployed on the Dartford Creek Barrier.

The barrier is part of London's flood defence system and works in conjunction with gates at Tilbury Docks and Canvey Island, the King George V Lock gate, the Barking Barrier and the famous Thames Barrier itself.

The Dartford Barrier is made up of two towers, each almost 30m high, that stand aside the Darent tributary river.

Between them are sections of barrier that are lowered into place sequentially to form a defensive wall against high tides.

The chain that drives the mechanism on the Dartford Barrier is over 90m in length and weighs 13 tonnes, with a breaking load of 285 tonnes.

This chain is tough and it has to be, for as well as having to bear huge loads when the enormous sections of barrier are raised and lowered, parts of it have to endure spending significant amounts of time submerged underwater.

To keep a check on the general well-being of this chain Renold has deployed the Smartlink data logging technology.

Smartlink consists of a strain gauge linked to a microprocessor which collects data about the stresses and forces the chain is exposed to during the lowering and raising of the barrier.

The Smartlink units are connected to the chain's side plates and the information they collect can be downloaded to a handheld device and analysed on a PC using software developed by Renold for this purpose.

After analysing data from the Dartford Creek Barrier it was discovered that the friction caused by the mechanism of the gates being opened and closed was higher than anticipated.

In turn this was causing the chain to experience loads towards the upper end of its calculated working load under extreme conditions.

By establishing this fact prior to the chain being damaged the maintenance team were able to review the mechanism's action to reduce friction levels and thus the loading on the chain.

The diagnostic capabilities of Smartlink give it the potential for a wide range of applications and is available with a choice of three levels of sophistication.

In its simplest form Smartlink acts as an overload detector.

It is operated with a small remote-control device and gives warning signals if the chain exceeds a predetermined load.

At this point engineers can inspect the system, find the cause of the overload and ensure that it is safe to continue running the machine.

The alarm conditions on Smartlink are then reset using the remote control.

To understand more about the working loads being applied to the chain drive there is a second, more advanced level of diagnostics.

In this case the same Smartlink device is used but a more sophisticated hand-held receiver is used with it.

Using this receiver a range of data can be downloaded from the device and evaluated on a PC.

This data can be used to determine the exact location of the load peaks in the chain drive and provides engineers with more diagnostic information about the whole system.

The most sophisticated version of Smartlink, like the one in use on the Dartford Barrier, is capable of collecting a wide range of data but normally requires the support of Renold's engineers and is used where there are unresolved issues or on safety critical applications.

In these cases Renold works in partnership with maintenance engineers to help resolve issues or monitor systems on an ongoing basis.

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