Chop hoop
The Chop hoop process is a variation on the
filament winding technology. Chop hoop is in fact a combination of a winding
process and spray up. The technique is primarily used for the production of
cylindrical storage tanks and agricultural silo’s. These tanks and silo’s are
not used for pressurised storage applications and need therefore to be less
strong than tanks made by filament winding.
The chop hoop process runs as follows: on a rotating mandrel a resin-rich
layer is sprayed which forms a corrosion and abrasion resistant inner layer of
the tank. After initial cure of the resin layer, glass fibre and resin is
sprayed on the mandrel with conventional spray equipment. At the same time
glass fibre rovings are wound around the tank in order to achieve sufficient
circumferential strength (hoop strength) of the tank.
The mandrel on which the tank is produced is partly collapsible. This enables
a rapid demoulding after the cure. When curing is complete (most of the time
done just at room temperature) the mandrel is collapsed and folded away in the
inside of the tank. The tank can then be taken away easily from the mandrel.
It is then finished with the necessary flanges and connections, top lid and
metal support structure.
