GRP pipes with Flowtite continuous filament winding technology

Flowtite filament wound pipes are built as a structural sandwich, using the Flowtite continuous filament winding technology. The high-strength continuous glassfibers resist the hoop stresses from internal pressure, while the chopped fibers provide excellent resistance to axial stresses, impact, and handling loads. The structural laminate consists of heavily reinforced skins, separated by a compact, reinforced silica-filled core to provide optimal bending stiffness. Together with the protective layers, this construction provides capacity to resist high internal pressures and maintains excellent long-term stiffness.

 

Flowtite pipes with Flowtite technology are manufactured using a continuous advancing mandrel process. This process allows the use of continuous glassfiber 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 lower cost. A very compressed laminate is created that maximizes the contribution from the three basic raw materials: Continuous glass fibre roving and choppable roving are incorporated for high hoop strength and axial reinforcement, and a sand fortifier provides increased stiffness by adding extra thickness. With the Flowtite dual resin delivery system, the equipment can apply a special inner resin liner for severely corrosive applications while using a standard type resin for the structural and outer portion of the laminate. Other materials such as a glass veil or a polyester veil can be used to enhance the abrasion, the chemical resistance, and the finishing of the pipe.

 

The filament winding manufacturing machine consists of a continuous steel band mandrel supported by beams in a cylindrical shape. As the beams turn, friction pulls the steel band around and a roller bearing allows the band to move longitudinally so that the entire mandrel moves continuously in a spiral path towards the exit assembly. As the mandrel rotates, all composite materials are continuously metered onto it in precise amounts with the help of electronic sensors. Firstly, mould release film, followed by various forms and patterns of glass fibres, embedded in a polyester resin matrix. The structural layers are made of glass and resin only, whereas the core layer includes pure silica. After the pipe has been formed on the mandrel, it is cured and later cut to the required length. The ends of the pipe stion are calibrated to fit the coupling.

The figure shows a typical cross section of a pipe laminate. This section, as well as the way of applying and placing the different raw materials, can differ depending on the pipe application.

Flowtite pipe wall structure illustration

1 Inner liner layer
2 Inner structural layer
3 Core layer
4 Outer structural layer
5 Exterior surface

Technical data Flowtite pipes with Flowtite technology

Main materialsresin, glassfibers, sand
Operating temperature-50 °C to +70 °C, higher temperatures may be considered for individual projects
Standard lengths12, 6, and 3 m, other lengths on request
Pressure rangePN 1 – 32
Expected service lifemore than 150 years
Corrosion protectionnone needed, as materials used are inherently resistant to corrosion
Hydraulic roughnessk = 0.029 mm (Colebrook-White)
Water jetting resistancetested according to DIN 19523