Fiberglass Pipe Production Process

GRP pipes are produced by either the Continuous Filament Winding or by the Reciprocal Helical Winding process. Both are considered as filament winding machines, which is the process of impregnating a number of glass reinforcement with resin, then applying the wet fibers onto a mandrel in a prescribed patter.

Continuous Filament Winder: A continuous winder is composed of a continuous steel band supported by beams which form a cylindrically shaped mandrel. The beams rotate, friction pulls the band around and roller bearings allow the band to move longitudinally so that the entire mandrel continuously moves in a spiral path toward the end of the machine.

As the mandrel moves, raw materials, like glass fibers, resin, aggregate (if needed) and surface veil are metered on in precise amounts under the direction of a programmable logic controller (PLC) and computer (PC). After pipe is cured a synchronized saw unit cuts the pipe to the proper length.

Continuous winding process is considered as the most efficient, since once pipe production starts, as described above, the production process continues and would only stop at the completion of full order. This process is considered continuous since it does not hold and resume at the completion of each pipe or pipe layer.

Reciprocal Helical Winding: is the process where the glass rovings, continuous roving specifically, passes though a resin bath for resin impregnation. Resin bath and glass directing comb are placed on a carriage that is driven back and forth at a very well controlled linear speed. Fiberglass, pre-impregnated with resin, are winded on steel mandrel that is rotating at determined RPM. The synchronization of carriage linear speed as well as the mandrel RPM determines the angle of which roving are winded on the mandrel, which is considered to be the glass winding angle, that is redetermined depending on the pipe requested property. For this reason, both the mandrel RMP and carriage speed are very well controlled by a computer program.

In this process, winding progress is in stages, were multiple linear movement of carriage would produce one layer of pipe thickness, and pipe thickness is composed of multiple layers, depending on required total thickness.

   

For all processes, GRP pipes are made from many layers, the main layers are:

- Inner liner, which is rich with resin and is to provide chemical resistance to the pipe and well as well as smooth inner surface. Inner liner thickness that could reach up to 2.5 mm

- Structure layer, which is forming the majority of pipe thickness. Pipe mechanical strength is mainly achieved by the structural layer.

- Outer liner, which is as well rich with resin and is to give environmental protection to the pipe thickness.