Articles & Case Studies

A BRAND NEW SLANT ON TANK COVERS

Posted: Tuesday 10th March 2009

Cover technology specialists Power Plastics have recently completed a unique odour control design, build and install project at the Ringsend Wastewater Treatment Works in Dublin Bay. The work, a ground-breaking industry first, was project managed by Enpure.

Power Plastics created a new £1.5m frame and fabric system to cover the lamella tanks at the site, which stands at the mouth of the River Liffey. In conjunction with an air purification plant, the installation prevents the spread of odours while still allowing safe access to the tanks for the workforce.

The Ringsend works are part of the €500m Dublin Bay Project which also incorporated a pumping station and a submarine pipeline bringing wastewater from the north of the city. It was completed in 2003, since when odours have been a recurring source of objections from local residents.

Complaints have been made to the European Commission and the matter has been raised in the Dàil, the House of Representatives of the Irish Parliament.

A FLEXIBLE, PRACTICAL SOLUTION

In order to provide an effective and permanent solution to this long-standing problem, Power Plastics were tasked with designing a means of covering the lamella tanks.

Their design was chosen over two other companies’ standard GRP cover proposals primarily because it provided easy access and a safe working environment for the workforce. The tanks require regular inspection, maintenance and cleaning.

The winning proposal was based around a rigid curved framework mounted to the tank perimeter creating 12 segmented bays into which pre-stressed PVC coated panels are inserted. Removal of one or more panels is a simple process which allows the workforce to enter without having to uncover the whole tank surface – which therefore keeps odour-escape to a minimum.

DETAILED PREPARATIONS

The site was thoroughly surveyed with laser measures and initial planning began. There were two significant restrictions to overcome when the first designs were being developed.

The Ringsend works has 12 lamella tanks, each measuring 37m x12.2m, arranged in two sets of six with very little room between adjoining tanks. The arc of the frame, which curves away from the tanks’ edges, was dictated by the need to allow the walkway to be used as a safe working platform.

And within each tank there are tracks for a skimmer to move along the surface. Very careful measurements (and the occasional bridging truss) were needed to allow the frame to be mounted without being compromised by the track mountings.

The frame itself on the finished design is a modular construction in aluminium, but it was only the last in a long line of different designs which were tested as prototypes at the Power Plastics base in North Yorkshire. Along with different materials for the inserted panels, and a variety of proposals for the gable end, every element was thoroughly examined until the perfect combination was achieved.

The chosen panels were created from pre-stressed PVC coated with PVDF lacquer. Cut, shaped and welded in Power Plastics’ own factory, the panels were delivered on-site with a curve already built-in.

Each panel has a keder edging on two sides which allow it to slide into grooves in the aluminium frame. A similar system is used in yachting to slide sail edges into grooves in the mast.

Once fully seated, the panels are pulled tight by straps and there is no creasing or fluttering.

A full working version of the new cover designed was installed at a Birmingham training site to make sure all components were performing properly before installation at Ringsend began.

CRANE-FREE, HASSLE-FREE INSTALLATION

One of the benefits of the modular nature of the system is that installation took place without the need for a crane on-site. It was, therefore, a faster process than traditional covers would demand – unaffected by wind and weather constraints – and gave significant cost-savings.

Part of the overall odour-control system is an air scrubber system using activated charcoal filters to provide constant purification, and the frame allowed for the fitting of all the relevant pipework and ducting.

Gable ends were fitted and, once the ribs were in place, the 72 PVC panels were located in their grooves and stretched taut. At this point the structure is more than 99% gas-tight.

Finally, the walkways’ plasma-cut struts for the hand-rails were installed.

Removing one or more of the panels is a two-man operation performed entirely from the safety of the walkway. The procedure can be taught in a matter of minutes, and the removal of one panel takes a practised team less than 90 seconds. As a result, inspection, maintenance and cleaning with high-pressure hoses can all take place within the demands of current legislation, including the ‘working in confined spaces’ rules.

And, of course, the swift removal and re-fitting of the panels keeps odour escape to a minimum.

To facilitate even more efficient inspection, the design incorporates lift-up aluminium panels at the weir end which also allow waste to be hosed away.

And with maintenance in mind, a gable end for each tank is removable which means the skimmer bridge can be hauled out completely and dealt with on safe ground.

Mention must be made of the finished design’s aesthetics, which go far beyond the merely practical to create a very pleasing architectural appeal, influenced by the curves and arcs of ocean-going craft.

SUMMARY

The system has an expected design life of 15-20 years. In normal use, the framework can be expected to last much longer with only the panels requiring replacement at only 10-15% of the original overall project cost.

Installation was completed on September 3 rd 2008, on-time and in-budget, with no extras. The installation process took four months out of a project timescale which stretched a mere seven months from signing the contract to completion.

At the time of going to press, Power Plastics have two similar installations of their unique design underway.

Tel: 01845 525503
Email: info@powerplastics.co.uk
www.powerplastics.co.uk




Read the magazine online

December 2018

About the magazine »
Magazine archive »


Advertisements

Information for advertisers »

Grundfos 2018
Pulsar Button June 13 Prominent Fluid Controls Huber Water Aid Verder British Water buttonwood marketing Harvey Communications wateractive
Sykes Pumps