Varicons Recent Projects

By fitting VACON 100 FLOW AC variable speed drives (VSDs) to the three main inlet pumps at Newbury sewage treatment works (STW) in Berkshire, UK, Varicon has made it possible for Thames Water to achieve large energy savings complemented by significant reductions in downtime. The energy savings alone will cover the cost of the VSDs and their installation in less than two years.

Fixed-speed soft start replaced with three separate VACON 100 FLOW drives

Thames Water continually assesses all areas of its operations to find opportunities for saving energy. The company determined that replacing the fixed-speed soft start used to control the main inlet pumps at Newbury STW with three separate VSDs would provide important energy saving benefits.

For assistance in carrying out this project, Ricky O’Sullivan, Technical Coordinator (Thames Water Swindon/Newbury Area Waste Operations), approached Varicon, the company that provides support and repairs for all of Thames Water’s VSD and soft start installations. Varicon, an authorised DrivePro®Service Partner, responded by proposing a competitive solution based on three of the latest VACON 100 FLOW VSDs, each rated at 55 kW.

Fitted adjacent to motor control centre

Varicon undertook the supply and installation of the VACON VSDs. Because of the lack of available space and difficult cable access with the existing motor control centre (MCC), the new drives were fitted adjacent to the MCC. This presented no problems as the version of the drive chosen has an IP54 ingress protection rating.

Significant benefits and short payback period

The new VACON 100 FLOW drives have completely eliminated ragging issues with the pumps at Newbury STW, and overall process control has been significantly improved. There are no longer surges when the pumps start as their acceleration is closely controlled and this has resulted in significant downtime reductions across the whole site.

“The project was completed with a minimum of disruption to our operations,” said Ricky O’Sullivan, “and we were extremely impressed both with the specification of the VACON drives and the quality of the work provided by Varicon. We’ll certainly hit our anticipated payback period of two years based on energy cost savings, but we’re actually getting much more in the way of benefits, and these benefits are sure to increase further over the traditionally challenging winter period.”

As a result of his experiences with this project, Ricky O’Sullivan is now looking at other potential applications within his area of Thames Water where he can work with Varicon and VACON VSDs to save money and improve process performance.

Developed specifically for pump applications, VACON 100 FLOW VSDs combine exceptionally high operating efficiency with the latest film-capacitor technology to ensure long life and lowest total cost of ownership. The drives also incorporate a range of pump-specific features as standard, including auto-cleaning and anti-ragging options, which detect when pump torque is increasing due to blocked pump and runs a user-defined cleaning sequence. This reduces risk of unplanned downtime in wastewater applications. The VACON 100 FLOW also has provision for multi-pump control and a real time clock that facilitates time-stamped logging of operating parameters and fault information.

In the Newbury STW application, Thames Water had found that using soft start control for the main inlet pumps caused large surges to the inlet screen system and, because of the small inlet size, this would weir over to storm. This resulted in a significant amount of rag moving through the plant, causing pump blockages throughout the site.

The inlet pumps were, in fact, subject to rag blockages on an almost daily basis, and the recent replacement of the pumps did not completely resolve this situation. Varicon is, however, confident that the auto-cleaning and anti-ragging features provided as standard by the VACON 100 FLOW VSDs would be the key to an effective solution.

VACON 100 FLOW product information

Newbury STW drives

Three VACON® 100 FLOW ac variable speed drives (VSDs) control the three main inlet pumps at Newbury sewage treatment works (STW).