Hampton WTW Slow Sand Filter Refurbishment

Customer: GBM

Site Owner: Thames Water

Value: £147k

FSD were awarded the electrical installation contract at Thames Water’s Hampton site in Surrey.

The panel manufacturer provided new control panels and sampling kiosks for each of the 25 filter beds at Hampton, along with three new master control panels – one for each of the 3 main filter bed areas.  FSD scope was to provide new fibre optic cabling from the master control panels to each individual filter bed, disconnect existing power and instrument cabling and reconnect into the new control panels when installed, install new free issue instruments and the new containment required.

Hampton is one of Thames Water’s key sites for supplying water to the London ring main as well as Greater London, so ensuring the each filter control refurbishment was completed within a short, agreed timescale coinciding with when a filter was taken out of service for cleaning was critical.  The panel manufacturer was also contracted to undertake the mechanical installation of the panels and kiosks, including additional instrumentation and sample pipework.  We worked closely with them throughout the project to ensure the installation work for each filter was undertaken in a quick and efficient manner , also assisting them with modifying their panel designs to allow the re-termination of the existing and new cabling as each filter panel had subtle differences that they had not picked up during their preliminary work.

Much of the instrumentation and cabling work needed to be undertaken within enclosed chambers beneath the control panels, by the filter outlet pipework – all of which were classed as confined spaces.  We provided confined space equipment and specially trained staff to not only work within the chambers, but to act as top-man when the panel manufacturer’s mechanical fitters were working within the chambers.  Again, good on-site coordination and cooperation meant both the mechanical fitters and our electrical engineers could work within the same restricted access and space areas for the filters without hindering or endangering each other or compromising the installation completion.

We subcontracted the new fibre optic cabling installation (over 4500m in total) to FB Taylor, and the filter bed control panel and master station patch panel terminations and testing were undertaken by ITM.  Having the fibre optic cabling installed ahead of the filter control panels arriving on site and left pre-coiled in each filter chamber, meant the panel changeover process was more streamlined and with less work and personnel required on the day of each changeover.

There were many challenges with this project, not only due to on-site hardware changes by the panel manufacturer, but also due to the criticality of the site maintaining output at all times; we were given very short notice of the filter bed shutdown schedule by Thames Water operational staff, so in most cases we had not more than 48 hours notice.  This meant we had to maintain a very flexible approach to site resourcing and also working hours, to achieve the filter panels according to the short-term needs of the client, rather than as we had programmed.  Approximately 65% of the filter beds were not released one at a time in a consecutive fashion, as we had anticipated, and instead were handed to us sometimes as many as four at a time, an issue we resolved by ensuring key resources were able to be assigned to the project at short notice from other nearby schemes, and also training further staff in confined space working to enhance our resourcing options. Our good, long term working relationship with our supplier and subcontractor ITM proved beneficial, as they were able to provide engineers at short notice to complete the fibre optic terminations and testing once each panel was complete.

Towards the end of the project, the filter issuing from Thames Water became more structured, and we were able to comfortably complete each filter installation within the originally planned five-day period – the same time as each filter was out for scheduled maintenance.  Also, the control panel modifications which needed to be made on site were coordinated by the panel manufacturer’s own newly assigned electrical engineer based on site, with whom our supervisor worked in partnership with and this proved to be a very successful working relationship, with the collaborative working with our client enabling the remaining filter beds to be installed with minimal issues.