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A large snack-food plant is using an Energair compressed-air management system to reduce energy bills by GBP27,000 per annum.

The process of helping the team towards achieving its target of a 10 per cent reduction in overall energy usage has included combining the compressed-air supply for two production operations on one site, integrating two retrofitted variable-speed drives, reducing system pressure and fine tuning compressor usage.

The energy savings have been achieved by applying a combination of system pressure optimisation principles, matching air generation to demand, ensuring compressors are working at their optimum speed and efficiency and operating compressors only when they are needed.

The central element of control included in both sites is an Energair SX control unit: a specialised supervisory and control module designed to provide optimised pressure and sequence management of all the air compressors on each site.

Nigel Clark, Energair’s regional manager, said: ‘The project began with an audit carried out on the two production areas that, until recently, used completely separate compressor houses and air ring mains.

‘Energair carried out a comprehensive audit that measured system pressure and air usage and benchmarked a series of key performance indicators before the change and upgrade,’ he added.

Analysis of the data led to a set of estimated results that predicted the energy savings achievable by fitting an Energair management control system and retrofitted VSDs at each site.

There are seven compressors in total, made up by three 160kW units and four 200kW units, and production runs for 24 hours.

Based on the overall cost of installing the system, balanced against the reduction in energy that could be achieved, the payback period was estimated at 18 months for the entire project.

Based on these predictions, the facility coordinator at the time ordered the Energair system and the retrofitted VSDs.

The system paid for itself after 18 months in operation, according to Energair.

The company claims that large plants such as this are continually changing and the level of visibility and fine control provided by the Energair software has enabled the facilities team to continue making savings and improvements.

For example, the team has connected the main air supply between both sites and uses the Energair system to optimise overall system pressure and air generation in both compressor houses – but controlled and working as one.

The plant has also been able to add another complete production line since the initial Energair installation, without having to upgrade the compressed-air generation facilities.

The compressors are also being used to generate hot water for the site.

There are also plans to use hot air vented from the compressors through a heat-exchange process for heating the building during the winter months.

Pressure sensors are fitted throughout the system and are used to feed live data into Energair’s Enersoft-Analysis data management software, which is hosted on an onsite PC.

This collates and records all the data and makes it available to the Energair Enersoft-Visual PC visualisation package.

The complete compressed-air system, from compressor through to the dryers and out across the plant, is represented visually on screen in a Windows environment, with key indicators such as system pressure and efficiency displayed on screen as analogue-style dials.

Through a series of SCADA-style screens, the operators can drill down and check on the performance of individual compressors, set threshold alarms for performance variables, schedule servicing and maintenance tasks and see the effect any changes have on the system immediately.

Using the Enersoft-Analysis data manager, any of the key performance indicators can be tracked over time and reported on at fixed intervals.

The data is updated every few seconds and the information seen on the screen is virtually live, making it easier to accommodate changes to the plant and make positive changes to keep efficiency maximised.

Prior to having the Energair system, the facilities team had to collate data over a period of time using much cruder indicators, such as energy bills, and it was a minimum of 10 days before results could be seen.

In that time, other factors could have cancelled out the improvement made and the team would never be completely sure how effective the change had been.

One aspect in particular that has shown savings and can be tweaked on site is the overall system pressure.

There are certain limits to how low it could go based on manufacturers recommended minimum operating pressures for machinery on the production line, some of which were set quite high.

The team has been able to safely reduce the overall system pressure by more than half a bar in increments.

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