Automation Technology Learn about an Innovative Approach to a New Motor Control Center
Water treatment is not the environment in which one expects to find state of the art automation technology — And yet, sewage treatment plants could benefit greatly from the latest developments in drives and process control systems. All that is needed is an open mind for innovative thinking and new technologies, as a major English water distributor experienced.
Severn Trent Water is the UK’s second-biggest water company, serving more than 3.7 million homes and businesses in England and Wales. The company delivers almost 2 billion litres of water every day through 46,000 km of pipes. A further 91,000 km of sewer pipes take wastewater to more than 1,000 sewage treatment works. The company has a positive attitude towards innovation: It has a formal advisory group, whose members come from both within and outside the company, to assess new approaches and technologies for the benefit of both company and customers.
It was this desire to explore new technology that led Severn Trent Water and one of its Tier 1 contractors, NMC Nomenca, to investigate the feasibility of advanced, integrated motor control centers (MCCs) from Rockwell Automation. The approach also included Form 2 construction: a proven, space-saving approach from other indus-tries.
Severn Trent Water gave engineers from NMC Nomenca the green light to investigate new technologies for a new inlet at Melton Mowbray sewage treatment works. The complete job involved replacing the current screenings, screens handling, and grit removal installation at the Lake Terrace terminal pumping station, which transfers raw sewage to Melton Mowbray.
Tight Space, New Thinking
The existing pumps at Lake Terrace will be retained, but the screening infrastructure will be relocated to Melton Mowbray. Given the space limitations and inherent hazards at Lake Terrace, the project gave the engineers the opportunity to consider new ideas for the site. Following an investigation by the ICA Community of Practice group and a competitive tender, MCC and associated technology from Rockwell Automation were chosen.
“We wanted to do something a little different with the MCCs,” explains Chris Webb, Contracts Engineer at NMC Nomenca and the company’s representative on the ICA COP group. “Severn Trent Water was looking for innovation in the new equipment and was also looking to save money (15 % compared to other solutions). I had a few ideas based around the MCC, especially relating to the use of Form 2 construction, which is not very common in the UK water industry even though it is in the current standards. As well as using Form 2 to reduce the overall size of the MCC, I also wanted to try out some different, contemporary technologies, such as those offered by Rockwell Automation.”
Innovation in Motor Control
The Form number defines the way the metalwork of the MCC is constructed: Form 4, a mature design based on older standards and less-reliable equipment, is currently the “normal” method in the water industry. Using Form 4, the motor starters would be isolated from each other and installed in separate compartments. A Form 2 MCC, however, requires just one compartment. Recent advances in equipment reliability make Form 2 not only possible, but also more desirable for installations with restricted space. Chris Webb presented his ideas for a Form 2 MCC to the Severn Trent Water ICA COP and in due course received approval to go ahead.