Articles & Case Studies

£1.7m UU tank contract

Posted: Thursday 21st February 2008

The growing usage of thermoplastic methods of construction of storage tanks to contain aggressive or corrosive chemicals has led to a rise in their market demand. Indicative of this growth is the announcement by Gee & Company that it has just been awarded a two-year framework agreement by United Utilities, valued at £1.7 million, for the design and manufacture of tanks and associated equipment for chemical storage.

With over thirty years specialisation behind it, Gee is well known for its advances within the chemical dosing market. Perhaps slightly less well known has been its parallel development in the tank market. Yet, as one of the companies that has driven this growth and taken the technology into new applications, the company has just announced that it is to invest in an expansion programme that will see a doubling of its tank manufacturing capacity.

In the early years, already involved in the design and manufacture of wastewater treatment systems, Gee struggled to find subcontractors to manufacture tanks. Explains Rob Lissner of Gee, “At this time, we were also taking on many effluent treatment projects in the electronics and automotive industries and our sources of tank supply were just too slow and inflexible”, he says. “So we decided to buy a plastic fabrications company and develop a manufacturing capability of our own. Speed of construction was vital. To meet fast-track programmes, it was necessary to construct the tank shell at the same time as final design consideration was given to branch positions”, he explains.

Vital weeks were gained by working in this way, typified in recent times by a contract for a new caustic dosing system and 35,000 litre sodium hydroxide reagent tank and bund for Southern Water’s Ashford WTW. This was designed, installed and commissioned in five weeks - a remarkable feat by any standards and certainly impossible without in-house manufacture.

So successful has Gee’s plastic fabrications division been over the last twelve months that the company has announced that it is to double the production space dedicated to this sector of the business and to invest in new overhead craneage to facilitate the handling of the large fabricated tanks.

“Another reason for the dramatic expansion of our plastic fabrications division was a result of Gee’s acquisition of the Systems Division of Michael Smith”, adds Rob Lissner. “This division’s KB and KTB dosing units both have a high content of thermoplastic engineering, the manufacture of all of which we have now moved in-house. KTB units are very substantial in size. For example, two recent systems involved the manufacture of 25,000 and 30,000 litre capacity tanks, housed in bunds that are constructed in fabricated enclosures,” he says.

The ability to work in many thermoplastic materials has empowered the division to become involved in the handling of a much wider range of chemicals. This, combined with some unusual manufacturing techniques to fabricate large tanks, is reflected in the design and manufacture for United Utilities of 180 tonne aluminium sulphate storage tanks. These large structures were also supplied lagged and heated.

Gee has also developed construction techniques, using special thermoplastics, for large capacity, conical-bottomed tanks of up to 60,000 litres capacity. These units, which were previously manufactured in steel, have been used for applications such as the storage of kalic and also for sedimentation tanks. Replacing steel for sedimentation tank applications - which invariably have highly corrosive liquid interfaces - makes them virtually maintenance-free.

This philosophy was used with good effect for a sludge holding tank with side entry man way that was commissioned for the BMW car factory in Oxford. The original specification called for manufacture to be in mild steel, which would have been chemically quite acceptable. However, given the strict environmental controls in the immediate vicinity, Gee decided to change the specification to polypropylene, a decision for which the user was appreciative.

The materials used by Gee are single polymer thermoplastics such as polypropylene and polyethylene, and also composite products such as polypropylene or PVC that are reinforced with GRP. Compared with single polymer tanks, these are favoured for their engineering and construction reliability. For this reason, although some producers use large capacity single thermoplastic tanks, Gee limits the capacity to a much lower level. This helps users to select the correct tank for the application, without over-exceeding the engineering properties of the materials of construction.

Concludes Rob Lissner, “There is a concern – that you will sometimes even hear voiced by the Health & Safety Executive – about the safety of tanks that contain corrosive chemicals. Gee believes that the correct way forward is to ensure that design and manufacturing techniques are maintained and held with the highest level of contingency”.

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