I want to know how they make big PE tanks?

Question

Do you see huge Poly ethylene (PE) tanks in chemical industries or power plants? I want to know about the manufacturing process of these tanks.

Answer 1

They are probably "roto-molded".

I very large tool that looks like the "outside" of the tank reversed makes up the "inside" of this tool. The tools is mounted on a 3 rotational axis gimbal, and is filled with plastic pellets.

The gimbal is then advanced into an oven where the tool is rotated on all three axes and the plastic "melts". The rotation assures even coating of the inside of the tool.

The tool is then advanced out of the oven and continues to rotate until the tool is cool enough for the plastic to set.

The tool is then opened, and the part removed.

Usually these gizmos are on a rotary transfer, 3 or 4 gimbals per unit. One "station" is the oven, one is fill, one is cool, one is unload. For 3 stations, unload and fill are shared.