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Materials of Construction

Forbes manufacture tanks and environmental technology systems in a wide range of materials in order to suit a full spectrum of contents and applications. Our experienced team can select suitable materials of construction to suit each individual application.

PP - Polypropylene

The most versatile tank construction material is polypropylene (PP). This material is widely acceptable within the chemical, water treatment, food, beverage, pharmaceutical and electronic industries. Copolymer polypropylene is the most versatile giving good impact resistance even at low temperature. Polypropylene offers:

The PP materials used by Forbes have WRc and FDA approvals. Polypropylene is also available to comply with the more stringent requirements of the DWI Regulation 31 through our Cheetah and Lion range of approved products.

Natural PP is generally only used indoors; its semi-translucency permits limited visual checking of contents levels. If used outdoors it will start to degrade from exposure to ultraviolet radiation (sunlight) in the longer term.

Black PP is UV-stabilised and quite suitable for long-term outdoor installations.

Key Points
  • Superb chemical resistance
  • Strength, resilience & impact resistance
  • Material is light in weight
  • Non-toxic, non-taint & odour free
  • Highly cost-effective
  • Ability to operate at higher temperatures than HDPE

GRP - Glass Reinforced Plastic

GRP tank technology is now accepted as standard in virtually every industry from chemicals to food and water, microelectronics and offshore oil and gas.

Forbes manufacture GRP tanks using both hand lay-up and machine based techniques.

Standard filament winding manufacturing techniques do not produce the ideal glass/resin ratio for process plant applications therefore, Forbes invested in a massive installation for the production of cylindrical GRP shells by the chop-hoop winding process.

Automated controls constantly monitor the rate of deposition of both glass fibre and resin and provide detailed quality records. The laminate is particularly strong and economical and combines all the advantages of winding and spraying techniques, notably considerable multi directional strength and enhanced inter-laminar shear when compared to standard filament winding techniques.

Where necessary for process reasons, tanks will be post-cured in accordance with the resin manufacturers’ specifications to ensure optimum physical and chemical properties in order to achieve maximum performance from the laminates.

Resin Selection

Choice of resin is important as there a vast range of resin types. Forbes specifies the correct resin for the application giving long-term resistance to the contents.

The external weather resistant resin rich surface can be pigmented to any colour required. Design life of 20 years is standard however life expectancy, proven by existing tanks in service, can exceed 40 + years.

The range of resins specified by Forbes includes:​
  • High chemical resistant isophthalics
  • NPG – isophthalics
  • Bisphenols
  • Vinylesters.

HDPE - High Density Polyethylene

A versatile tank construction material high density polyethylene (HDPE) comes in various grades.

For chemical tank & other chemical applications Forbes use PE 100 as the preferred material.

There are lower grades of HDPE which offer less chemical resistance & in particular are susceptible to environmental stress cracking. HDPE is not so heat-resistant to high temperature when compared to polypropylene. PE 100 material is widely acceptable within the chemical, water treatment, food, beverage, pharmaceutical and electronic industries.

The HDPE materials used by Forbes have WRc, FDA approvals and also complies with Regulation 31 for use in the public water supply through our range of Jaguar tanks.

HDPE – PE 100 is pigmented black to give full UV-stabilisation for long-term outdoor installations with a design life of 20 years.

Key Points
  • Superb chemical resistance
  • Strength, Resilience & Impact resistance
  • Material is light in weight
  • Non toxic, non taint & odour free
  • Highly cost-effective
  • Ability to operate down to -40c

Other Materials

PVDF - Polyvinylidene Difluoride

A high performance material being especially resistant to aggressive chemicals at higher temperatures. Should not be used for Caustic applications.

Due to the high cost, PVDF is generally only used for tank manufacture as a relatively thin inner corrosion resistant shell with GRP reinforcements to give the required mechanical & structural stability.

ECTFE - Ethylene Chloro Trifluoroethylene Copolymer

An exceptional high performance material. At temperatures up to 120° C the polymer is not affected by stress cracking nor attacked by the majority of chemical reagents.

Whilst ECTFE offers one of the best chemical & temperature resistance, there is a price to pay – this being almost 10x the cost of Polypropylene.

Due to the very high cost, ECTFE is generally only used for tank manufacture as a relatively thin inner corrosion resistant shell with GRP reinforcements to give the required mechanical and structural stability.

UPVC - Unplasticised Polyvinyl Chloride

PVCu offers excellent chemical resistance when used with strong oxidizing and reducing chemicals (such as high concentrations of Sulphuric Acid or very strong oxidizing agents) and is especially suited for the storage of Chlorine based compounds such as Sodium Hypochlorite.

PVCu is generally only used for tank manufacture in conjunction with suitable GRP reinforcements due to its poor impact resistance and general brittle nature if not externally supported with a GRP structural laminate.

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