Glass-reinforced plastic delivers benefits

Louise Smyth

Don’t overlook GRP for sludge processing plant, advises Andrew Shedden

Wastewater treatment processes can involve some harsh operating conditions that pose a particular challenge for the manufacturers and operators of treatment equipment.

Glass reinforced plastic (GRP) is an attractive, modern material that can deliver many benefits for the construction of equipment used in activated sludge processing plants.

Sometimes referred to as fibreglass, GRP is composed of many millions of individual strands of glass, each one very fine, collectively formed into a fabric-like sheet. This is used to line a mould and is then set solid by the addition of a resin to which a catalytic chemical has been added so that it quickly hardens.

Normally the GRP is applied in layers, with each one hardened before the next is added.

The result is a multi-layered material, shaped into a useful object that is strong and lightweight. Today we are all used to seeing GRP used in water tanks, canoes and countless other everyday products. It is also a favourite material with engineers who are pushing the boundaries of technology.

For instance aerospace engineers fit it in the latest supersonic, ultra manoeuvrable jet fighters, while civil and water engineers have found it really useful in developing a new generation of equipment for sludge processing plants.

Using in-house 2D and 3D CAD design and full materials traceability, coupled with extensive NDT (non destructive testing) and inspection regimes, A&J Fabtech can guarantee the quality of its equipment and project management skills for even the most critical of applications.

Around a sludge processing plant the company will recommend the best type of equipment for each individual situation. For instance, it may recommend GRP for water and sludge processing equipment such as diffusor drums, energy dissipating drums, launder systems, McKinney baffles, scum boards, Stamford baffles, tank covers, weir boards, to name just a few.

There are several advantages of GRP, the most attractive of which is corrosion resistance. In this respect GRP outperforms steel, timber and other traditional construction materials, so is particularly appropriate for the harsh and corrosive environment of a sludge processing works. In many installations GRP will outlast steel by a very wide margin, giving operators a considerable and on-going cost saving in terms of maintenance and replacement.

GRP is very light in weight and this belies its strength. It is about 50% the weight of aluminium or 15% the weight of steel. This makes it easier, safer and cheaper to handle during installation and means it requires less support once in place. These characteristics can be particularly important for pipes and tanks and also for projects based on retrofitting new, or replacement equipment within existing installations or in elevated locations.

High strength

A major consideration in virtually all material selection decisions is strength, and GRP does not disappoint in this matter. It can be used for rigid and self-supporting structures, is well appreciated by pipe and duct makers and is easily formed into unusual shapes. It can also be used to mould one-piece tanks, drums, etc. that have integral supports and other structural elements, plus it benefits from a lack of seams where leaks or weaknesses can develop.

There are not many engineers who do not have to worry about project costs, and when looking for a low-cost, high-performance material, GRP is often the answer. In fact, compared with exotic metals such as stainless steel, titanium and Hastelloy, or complex solutions such as special tank linings and vacuum impregnated materials, GRP is often a tiny fraction of the cost. It is impossible to give an approximate equivalent cost because each job is unique in terms of design and production processes, but it is almost unheard of for GRP not to be very cost competitive.

The final advantage is that of flexibility. The simple moulding technique used to produce GRP equipment gives it a distinct advantage over other materials that require complex production processes. In mass production, reusable moulds are used again and again so that their cost of production is spread over a long manufacturing run; for one off pieces often a cheap sacrificial mould can be used.

GRP is a very versatile material that can be used in a wide range of installations, often as a direct replacement for more expensive traditional solutions. Furthermore, for one-off projects it can provide a quick, cost effective and easy solution to almost any job.

Andrew Shedden is with A&J Fabtech

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