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Amitech South Africa (Pty) LtdP.O. Box 12405132 Potgieter StreetAlrode (Johannesburg) 1451South AfricaTel: + 27 11 864 20 40Fax: + 27 11 864 20 41info@amitech.co.zawww.amiantit.com

AMITECH SOUTH AFRICA – CUSTOMER MAGAZINE 3rd EDITION 2009

From the beginning, GRP was used in pipes in the chemical industry due to its excellent corrosion resistance. In Norway, the production of pipes started at the end of the sixties. The oldest Flowtite GRP pipes in Norway are more than 35 years old.

Today GRP pipes are used in more and more applications due to its excellent mechanical and chemical properties. Namely: Pressure Sewer, Hydropower, Raw Water, Potable Water, Desalination & Sub aqueous to name a few.The basic raw materials used in the manufacture of FLOWTITE GRP pipes are resin, fibreglass and silica sand. The walls of all GRP pipes consist of an inner liner, a mechanical resistance layer (core) and an outer layer.

GRP pipes branded as “FLOWTITE” are manufactured using the continuous advancing mandrel process, which represents state of the art GRP pipe production. This process allows for the use of continuous glass fibre reinforcements in the circumferential direction. For a pressure pipe or buried conduit, the principle stress is in the circumferential direction. Thus, incorporating continuous reinforcements in this direction yields a higher performing product at a lower cost. Using technology developed by material specialists, a very dense laminate is created that maximises the contribution from the three basic raw materials. Both continuous glass fibre rovings and choppable rovings are incorporated for high hoop strength and axial reinforcement. A sand fortifier is used to provide increased stiffness by adding extra thickness, placed near the neutral axis in the core. With the Flowtite dual resin delivery system, the equipment has the capability of applying a special inner resin liner for severe corrosive applications, while utilising a less costly resin for the structural and outer portion of the

The manufacturing of GRP pipes at AMITECH South Africa

FLOWTITE pipe - wall build-up

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TECHNICAL

laminate. Taking advantage of the winding process, other materials such as a glass or polyester veil can be used to enhance the abrasion resistance and the finishing of the pipe.The cross section of a pipe laminate as well as the method of applying and placing different raw materials, can differ depending on the pipe application.

GRP Pipes branded as “VECTUS” are manufactured by a discontinuous filament winding process whereby resin-impregnated continuous glass fibre rovings are wound around a rotating mandrel with a computerised process, until the required design wall thickness of the pipe is attained. All influential factors and processes for the pipe build-up are predetermined by a computer

programme which controls the manufacturing process.The pipe wall has an integrated structure consisting of three different layers The inner liner is a chemically resistant, flexible liner and applied around the mandrel. This liner provides resistance to corrosive materials and abrasion, and ensures impermeability of the pipe wall. The surface of the liner is extremely smooth with a thickness of about 1mm.The mandrel with the inner layer is then placed into a curing station to cure the liner for a predetermined period, depending on the design of the pipe. Afterwards the mandrel is then moved to the winding machine where the mechanical resistance layer is

wound onto the liner. Strands of resin-impregnated continuous glass filament rovings are wound over the pre-cured inner liner under controlled tension and at a predetermined helix angle (typically between 50 and 70 degrees, measured relative to the pipe axis). The angle is carefully selected to impart the strength and stiffness properties that will meet the expected load conditions for which the pipe is designed. The number of strands applied depends on the wall thickness required. This layer has a glass content of about 70% by weight and its stiffness can be further increased by the addition of silica sand.The gel coat or outer protective layer has to resist weathering and scuffing during handling, and to ensure complete impregnation of the peripheral glass fibres.

To ensure these properties, a resin-rich outer layer (optionally containing ultraviolet inhibitors) is applied over the mechanical resistance layer. The mandrel is then moved to the curing station for final curing and afterwards brought to the machining station where the grooves for the double o-ring seal are cut and the pipe prepared for extraction.The final process in manufacturing is the extraction where the pipe is extracted off the mandrel. Final finishing of the pipe is then conducted.In Africa, the first VECTUS pipes were manufactured in South Africa in 1992 and the first FLOWTITE pipes were manufactured in Botswana in 1994.

Outer Layer Mechanical Resistance Layer Inner Layer

FLOWTITE material application area

VECTUS winding process

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The third phase of the Sheffield Waste Water Works project is approaching closure and, with all three phases of this project bearing GRP pipes from

Amitech South Africa successful in Sheffield waste water project

Amitech South Africa, provides a great opportunity to highlight this GRP success story.

The project is being undertaken on behalf of client, Siza Water – a water service utility in the Illembe district, on KwaZulu Natal’s north coast, that manages the area from Tinley Manor to Tongaat. Nicky Misra, Siza Water project manager, approved the use of GRP in all three phases of this project which he says is critical for the company.

The entire project comprises PN 10, SN 5000 GRP pipes, with both, continuously wound FLOWTITE and discontinuously wound VECTUS being used and supplied by Amitech South Africa. Various diameters have been used including DN 450, DN 600, DN 700, DN 800 and DN 900. The pipe length exceeded 3000 m and was tested and passed.

VECTUS was used where short lengths of pipe were required, as the manufacture process allows for a single pipe to be produced at a time. Where longer lengths were needed, FLOWTITE was used, bringing additional cost savings to the project. This flexibility provides the client with a consistent piping material, which greatly aids maintenance and internal controls.

Misra and colleague Gerrie Lombard note that the process of selecting the correct piping material for a project involves several steps. First, the engineers are

PROJECT

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Imprint

Amitech South Africa (Pty) LtdP.O. Box 12405132 Potgieter StreetAlrode (Johannesburg) 1451South AfricaTel: + 27 11 864 20 40Fax: + 27 11 864 20 41info@amitech.co.za

Editor in chief:Cathleen van den Berg Tel: + 27 11 864 20 40Fax: + 27 11 864 20 41E-Mail: cathleen.vandenberg@amitech.co.za

Utmost care has been taken to ensure that all contents of this publication are accurate. However, no responsibility is accepted for any problems, which may arise as a result of errors in this publication.

informed of the business requirements at design stage; then the engineers provide the client with material and design options; and finally the client makes a decision.

According to Misra and Lombard, this decision is based on three key factors: initial cost of material against budget; long-term cost of maintenance; and reliability of material – track record and history of the material.

While Siza Water was prepared to act on the advice of the project engineers, it also relied on its own positive history with GRP to inform its decision. The company took over a GRP line from Avondale to Blythedale that was installed by Umngeni Water in the early 1990s. No maintenance is required on this line, and to date none has been done. This provided Siza Water with great confidence in using GRP pipes in appropriate projects.

This same line was discussed with engineer, Morrell Rosseau of Stemele Bosch Africa. Rosseau has extensive experience in the water industry and is well known and respected in KwaZulu Natal. He said he considered the alternatives of HDPE, concrete, steel, uPvc and GRP, but proposed GRP for a number of reasons, including:

• GRP’s resistance to hydrogen sulphide gas, which is released in sewer lines; this gas can be exacerbated

with the lower flow of waste, so resistance to this material was required;

• GRP’s ‘true’ grade, which meant that the engineer could rely on the fact that the grade would be consistent and allow for consistent flow, which is not the case in all piping materials;

• Installation is cost effective and easy;

• Long-term cost of ownership is low due to maintenance not being required;

• The stiffness of the pipe is good, allowing for loading conditions, which was not the same for all alternative materials;

• Flow characteristics are comparable with alternative pipe materials;

• The direct cost of the pipe is favourable, so it was possible to do the project within budget constraints.

Both client and engineer are happy that, from a piping perspective, GRP has delivered on commitments and has provided a pipe that will meet the requirements at a cost that is favourable in the market. Both maintain they will continue to use GRP, manufactures from Amitech South Africa, for appropriate projects in the future.

Project details:

Sheffield Waste Water Works Project Report

Client: Siza WaterEngineer: Stemele Bosch AfricaContractor: BPB Construction

PROJECT