Switched on thinking

Lighthouse automation reaches new heights thanks to the application of industrial computers which are usually more at home on the factory floor. Jon Excell reports.

The so-called ‘dark factory’, a windowless factory facility in which robots have replaced humans is said to be the inevitable outcome of industrial automation.

But one exception to this trend is the UK lighthouse network – an entirely automated industry where the lights have remained firmly switched on. A steady programme of automation means the days of the lighthouse keeper are long gone. Indeed, the last manned lighthouse was converted to automatic operation in November 1998.

However, while the largely proprietary systems put in place have done the job admirably, recent developments in automation technology have opened up a range of possibilities. This has allowed the Trinity House Lighthouse Service, responsible for the efficient running of most of the UK’s lighthouses, to introduce a new state-of-the-art centrally-controlled remote system, developed in conjunction with automation specialist Omron.

Automation of lighthouses can be traced back to 1910, when acetylene gas-powered lights controlled by sun valves were installed in a number of lighthouses. The sun valve was developed in 1907 by Swedish engineer Gustaf Dalen, who won the Nobel physics prize for his efforts and went on to invent the AGA.

Dalen’s valve, which uses sunlight to turn a lighthouse beacon on and off,consists of a central, blackened, light-absorbing metal rod surrounded by three reflective metal rods. In darkness all the rods are the same temperature and length. However, at dawn the blackened rod absorbs light energy and becomes warmer than the shiny ones. This causes it to elongate and trigger a device that cuts off the gas and switches off the light. When dusk falls, the blackened rod contracts, the gas valve opens and a small pilot flame lights the beacon.

But while the valve began lighthouse automation, keepers remained until the early 1980s, when lantern-top helipads offered easy maintenance and remote control technology was perfected.

Trinity has been running its own automated system for a number of years. Control systems in its lighthouses are linked to a telemetry system that sends and receives data to and from the company’s Harwich operations centre. The system determines rotation frequency, monitors the current and voltage profiles of lamps in order to pre-empt bulb failure and even automatically replace damaged bulbs. But the system is ageing, and support costs are rising.

‘We need to know what can be scheduled into routine maintenance and what demands that we send a team out straight away – the cost of mobilising a helicopter and an emergency repair crew at a moment’s notice can quickly run into thousands,’ said Trinity project engineer Richard Tomkins.

Add to this the growing risk of component obsolescence and the fact that downtime on what is essentially a life-saving operation is a potentially far more serious problem than factory downtime, and Trinity decided that it simply had to modernise.

The new system uses Omron PLCs, linked into the existing telemetry database. It has an open architecture – meaning that it is compatible with hardware and software from a variety of vendors – and has low power requirements consistent with an ongoing move towards solar and wind powered lighthouses. The system is also able to monitor both analogue and digital inputs.

Omron’s Paul Downey said that the true benefits of the system will be felt in the longer term. ‘the benefits of this system is the provision to do an awful lot more, and the future potential for constant improvement,’ he claimed.

The first lighthouse to be fitted with the system is Cromer in Norfolk.

Trinity is currently in the process of rolling out the technology across its entire network of lighthouses, radar beacons and GPS reference stations.

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