Temporary power for maintenance
January 1st 2008

When maintenance work is being carried out in industrial premises such as large factories and processing plants, managers will want downtime kept to a bare minimum. In these circumstances, the provision of temporary power services can make a huge difference, as Tommy Conway, technical support manager from Aggreko UK explains

With all its associated costs of labour, materials and downtime, maintenance can be a serious drain in the running of any factory or plant.

The evolution of new technology and the added complexity of the next generations of factory equipment – from increased automation to robotics - means that these costs are only going to increase.

Within manufacturing there are two types of maintenance activity: scheduled maintenance as part of a planned programme to ensure the operation continues to run smoothly and help identify any potential problems; and emergency maintenance after an incident.

Either situation can mean having to disconnect the power supply to the entire plant or process so that work on areas such as the switch gear or transformer can be carried out.

The best solution is to put in a temporary power supply from a generator, which will act as a utility provider directly to a specific line or the plant.

There are two options available when setting up a generator, depending on whether or not the manufacturer can go without power for a very short period. If this is the case then it is possible to run a generator with an Automatic Mains Failure panel (AMF) which monitors incoming power supply from the mains grid. In the event that this is disconnected, the AMF panel will start a standby generator. When the original supply is re-instated, the panel switches back to monitoring the mains supply and stops the generator.

With this set-up there is a break both when the generator first starts and when it stops. This option is ideal as part of a planned maintenance programme, which can be conducted at periods of low production when the interruption is less critical.

Alternatively, if going without power is a major problem – which may, for example, affect other processes down the line, and the quality of the end product - then it is possible to use generators that can recognise when there is no mains power supply and then take over. Zero synchronisation, as it is known, involves installing generators that continuously run, monitoring the electricity waves from the grid. The generator is sychronised to three phase 50Hz with the grid, so that having recognised there is a dip in power supply, it automatically takes over the load.

This means the plant can continue to run, minimising downtime and protecting any process that requires constant operation.

Another argument for having generators onsite is in the event of a power failure from the grid. The likelihood of this happening grows greater in poor weather.

With the current infrastructure struggling at times to meet demand, the chances of power outage increases. In this situation, an appropriate generator set-up is ideal to ensure operations can continue and minimise disruption to production lines.

When looking to hire a generator, it is important to work with a specialist company, such as Aggreko UK, which can help identify the most suitable set-up for your company's operations. This is because with a generator – as with any other machine that provides power to a process, such as a compressor - output needs to meet demand for it to work efficiently. Using a generator that is oversized for the amount of energy required and working under capacity can cause just as many problems as a machine that isn't producing enough power. It is necessary to consider the type of load demand of the premises - such as low power loads, leading power loads and Total Harmonic Distortion (THD) - which can otherwise have a detrimental effect on switchgear, cabling and alternators.

As well as considering the size of generator required to meet the plant's energy needs, it is important to plan the location of the generator. If, say, it needs to be situated close to the point of use, this may dictate the need for silenced canopied generators which lower the noise level of the machine.

Other important considerations include the specification of cabling and pipework - which carry the load to the process line - fuel supply and compliance with the G59 regulations, which cover the use of generating plant running in parallel with the grid. Aggreko UK provides additional fuel tanks to allow the generators to run for longer periods than are possible using only the generator's built-in tank. For added peace of mind, Aggreko UK also provides a fuel-management service to deliver top-up fuel to site before equipment runs dry.

The old saying "time costs money" is never truer than in manufacturing, so putting measures in place that can improve productivity - and the bottom line – should be standard practice when planning for maintenance work. The right generator set-up can make a big contribution to that planning whether for ongoing maintenance or emergency back-up.

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