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Liquid Handling


Underground solution Two underground spillage tanks for waste treatment works


Specialist manufacturer of Niplast bulk storage tanks, STF of Stockport, has completed the design, supply and commissioning of two 10,000 litre thermoplastic tanks, each now buried 1.5 metres below ground at two North West waste treatment works. Used for the emergency collection of spilt chemical, the tanks’ construction exceeds the requirements of BS EN 12573, the current European code for welding static non-pressurised thermoplastic tanks. The waste authority’s main contractor approached STF Niplast after identifying the need for underground emergency spillage tanks following a review of potential hazards at the treatment works. A spillage capacity of 10,000 litres was calculated as being required at each site for the possible storage of chemicals including a variety of treatment acids and alkalis. STF Niplast’s engineers designed the two tanks to be built from UV-stabilised co-polymer polypropylene, chosen for its chemical resistance and lightweight nature. Their calculations


had to account for a number of criteria including the internal pressure from the chemical, the external pressure from the soil and pedestrian loads and the floatation effects of the local water table.


Each tank has a 2750mm square footprint, stands 1700mm high and features 30mm thick polypropylene walls with on-edge thermoplastic horizontal ribbing to both the tank exterior and interior. Internal access is possible through 900mm diameter manways, supplied with lockable lids and internal grab handles. Other tank furniture includes screened vents, flanged connections for tank loading and level detection and an outlet connection extended to the tanks’ bases. STF Niplast fulfilled the order within 8 weeks from placement, including submission of engineering drawings, manufacture and factory acceptance trials, which involved hydrostatic and electronic spark-testing to verify weld integrity.


For more information visit: www.niplast.com


www.solidsandbulk.co.uk


October 2011 • Solids & Bulk Handling 37


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