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Case Studies

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Alwen WTW

OSS worked closely with Black & Veatch, on behalf of DCWW, to deliver a new Rapid Gravity Filtration Plant at Alwen WTW in Deeside, North Wales. The existing SIEMENS APACS Control system with PCS7 OS SCADA was expanded to include a new control system node and SCADA client. The project was delivered within tight timescales and close liaison with the other disciplines on the scheme was essential. More details on the scheme can be found on the following link:

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Cwellyn WTW

New Dissolved Air Floatation and Rapid Gravity Filtration plants were built and constructed at Cwlleyn WTW in the heart of Snowdonia. OSS provided the expertise to develop and commission the APACS/PCS7 OS control system software to meet the DWI date. It was a highly successful project, resulting in an award for OSS from the AMA alliance. Details of the case study can be found within the following Water Projects Online article:

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Llyn Conwy WTW

Under the Black and Veatch Go to Green programme, the control system at Llyn Conwy WTW was migrated to the new Mitsbushi Servelec solution to align with DCWW's Automation strategy. A technically challenging project, OSS were drafted in to assist with the development and commissioning of the new system control system working closely with MCC suppliers GPS, to get the project delivered to the satisfaction of all parties. Details can be found on the following link

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Mynydd Llandegai WTW

Mynydd Llandegai WTW was expanded to include a CocoDaff plant to address water quality issues from the raw water supply. Following on from a successful Siemens PCS7 control system migration project towards the end of 2009, OSS were contracted to extend the control system to include a number of intelligent MCCs and Profibus instrumentation networks. The new plant was successfully commissioned in isolation before being integrated within the mains works simply by adding the new Profibus networks to the existing AS controller. The project was a great demonstration of innovative use of technology to mitigate disruption to existing plant operations. A detailed case study can be read here:

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Maple Brook Pump Station

As part of the refurbishment programme of Maple Brook Pump Station, OSS's electrical division undertook the electrical installation contract, working closely with Imtech Process on behalf of South Staffs Water. Further details of the scheme can be found here:

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Nantybwch WTW

A water treatment works (WTW) in South Wales has had its control system completely upgraded, without disruption of supply to the population of around 70,000 people it serves.

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Dwr Cymru Welsh Water, The Nantybwch WTW

A water treatment works (WTW) in South Wales has had its control system completely upgraded, without disruption of supply to the population of around 70,000 people it serves.

The Nantybwch WTW, owned and operated by DCWW, has been supplying potable water to the towns of Tredegar, Ebbw Vale and Bargoed in South Wales since the works was first built in 1993. The original control system needed upgrading and local framework system integrator Oasis Software Solutions (OSS), from nearby Monmouth, was brought in to help with design, installation and commissioning. It was realised that enhancements could be made on multiple levels with a new control system, for which Welsh Water selected state-of-the-art Mitsubishi Electric technology.

The towns served by Nantybwch are expected to see population growth in the coming years, something the water supply needs to be able to accommodate.

Nantybwch WTW usually supplies around 20 megalitres of potable water per day, but has a maximum design capacity of 30 megalitres per day. Its catchment area is the mountainous eastern side of the Brecon Beacons National Park. Most water treatment processes tend to be similar, but each has to be adapted to account for local conditions, perhaps filtering out certain minerals or organic compounds. At Nantybwch, the quality of the water held in the reservoir is good, so a straightforward process is used. The primary treatment is based on dissolved air flotation (DAF), followed by two stages of rapid gravity filters.

In fact, the architecture of the final design provided a system that comprises of two pairs of redundant Mitsubishi Electric Q25 programmable logic controllers (PLCs) in the main works and a Q06 PLC in the pumping station. Each redundant system has two central processor units (CPUs) and a mix of traditional I/O and remote I/O. The remote I/O is connected in a number of different networks, some using fibre optic MELSECNet/ H and others using Profibus. "The mixture of technologies used for the remote I/O solutions demonstrates the flexibility and versatility of the Mitsubishi Q Series product. Where the system required low density I/O and a Profibus network already in place to interface a number of drives, a slice I/O solution was deployed. For critical areas of the process, a redundant MELSECNET/H solution was provided with the capability of utilising high density I/O modules, connected to a high speed, high integrity, fibre optic network. A fibre optic Ethernet ring was installed to provide peer to peer PLC communications and SCADA networking, offering a modern, future proof interface adhering to the DCWW AS427 Industrial Network Communications standard.", explains Neil MacDonald, Managing Director of Oasis Software Solutions.

Mitsubishi Electric Q Series PLCs are designed to provide a high functionality platform for automation, suitable for a wide range of applications across the full spectrum of industrial sectors. Of particular interest to the water industry, they can offer a high level of system redundancy, which ensures complete immunity to process interruptions caused by power or system failures. This is achieved by using a fully redundant architecture, which duplicates processors and network links. Hot-swap capability provides an operational level of redundancy.

The dual redundant CPUs (control and standby) mean that any failure of the control CPU causes immediate transfer of control to the backup, preventing system failure or interruption. Synchronisation of up to 100,000 words of process data is possible between CPUs per scan.

Switchover time is typically around 20-40ms, ensuring a 'bumpless' transfer. Because the CPUs reside on physically separate racks, the control CPU can be replaced while the backup maintains system operation. Most parts are interchangeable with standard Q Series systems, which helps to control both purchase cost and total cost of ownership.

Other aspects of the project that contributed to the overall improvement included upgrading and augmenting existing instrumentation, replacing existing variable-speed motor drives, modifications to improve the water treatment process, replacing local loop controllers and panels and a new SCADA (supervisory control and data acquisition) system.

Work started on site in summer 2013 and the plant was running entirely on the new system by mid March 2014. "There is a lot of satisfaction knowing that we have played a part in the regeneration of the regional economy of the Heads of the Valleys," says Neil.