Lamellar filament winding

(published on April 2010 – JEC Magazine #56)

VEM is an Italian manufacturer of filament winding equipment that specializes in the design, construction and installation of filament winding plants for the manufacture of GRP/GRE pipes, tanks, pressure vessels and poles. VEM’s patented machine produces GRP/GRE pipes ranging from 100 to 800 mm in diameter with or without sand filler. The pipes have high hoop and axial strength which makes them suitable for low- and medium-pressure applications.

The products wound on the Lamellar Machine can be used in a broader range of applications than conventional continuous wound pipes, including:

• Water transportation: fibreglass-reinforced polyester/vinylester pipes for potable, industrial and waste water transportation;
• District heating: fibreglass-reinforced epoxy pipes with hydrolysisresistant liner and external polyurethane foam covered with a PE coating for distributing the heat generated by centralized plants to end users;
• Oil, gas and chemicals transportation: high-axial-strength fibreglass-reinforced epoxy, phenolic or vinylester pipes with a gas barrier and corrosion-resistant liner for industrial applications and extraction sites;
• Marine and fire-fighting systems: fibreglass-reinforced epoxy pipes for flame resistant/retardant applications.

The lamellar plant

Compared with traditional continuous plants, the Lamellar Plant is characterized by: the possibility of producing ND 100-300 mm pipes; higher productivity; compact overall size; reduced manpower and maintenance; reduced downtimes; instantaneous stiffness regulation (MSR); heat transfer system for preheating the mandrel (HTS); online cross-winding of continuous roving for additional axial strength; UV and thermal curing system; online pipe insulation by PU foaming with PE coating; and axial strength through cross winding.

Most of these features result from the use of VEM’s lamellar mandrel instead of a steel band mandrel. The lamellar mandrel is formed by a shaft with supporting spacer discs calibrated according to the nominal diameter of the pipe under production. The disk grooves house the lamellas, mounted parallel to the shaft axis and to each other in order to form the mandrel surface. The lamellas assembled on the shaft are actuated by the cam system. A forward/backward movement of the lamellas drives the pipe under production over the mandrel towards its end, thus securing non-stop production.

The use of this innovative type of mandrel does not substantially affect the process, which remains analogous to conventional plants. The application of raw materials follows the standard sequence: the fibreglass, resin and sand are fed in due position according to the pipe design. The pipe is then cured and cut to metered lengths. Despite all the similarities this machine shares with steel-band machines, it offers a number of specific features: for instance, arriving at minimum diameters inaccessible to steel band plants, as well as the reduction of the downtimes caused by steel band breakages, thus increasing the overall efficiency of the factory.

The MSR feature enables the operator to regulate the internal pipe diameter and to change the required pipe stiffness before production. While the pipe outer diameter is determined by AWWA and ISO standards, the operator can adjust the inner diameter to achieve the required pipe stiffness. The instantaneous regulation reduces the time needed to change from one stiffness class to another (1 minute instead of 6 hours). The cross winding feature developed for the Lamellar Machine allows the on-line helical winding of the continuous roving on the advancing mandrel at a pre-set angle, resulting in enhanced axial and circumferential load strength, fundamental for above-ground installations and in oil and gas applications.