SHOT BLASTING Plates and sections are in most cases now shot blasted
to remove rust and millscale. The principles of shotblasting are dealt with in
Chapter 27.
Shot blasting plant in shipyards is generally of the impeller wheel type
where the abrasive is thrown at high velocity against the steel surface and
may be re-circulated. The plant can be so arranged that the plate passes
through vertically, but more often it is installed so that the plate may pass
through in the horizontal position. In the former case equipment must
be provided to allow the plate to be raised into the vertical position from
the roller conveyor before it enters the blasting plant, and to lower it on
removal. There is a further problem with lighter plate which may more
easily distort when stood on end. The only disadvantage of the horizontal
plant is the removal of spent abrasive from the top of the plate, which may
be relatively easily overcome. A separate shot blast plant is often installed
for sections.