Grain flow pipes are generally not square, but more commonly round section pipes. Round pipes are preferred to ensure smooth transportation of grain and to avoid damaging the product during flow. However, in some special cases or in accordance with certain design requirements, square tubes can also be used.

Square pipes generally have a more limited usage area and are preferred for certain applications. For example, square pipes may be used for special equipment or facilities where the shape of the pipe must be square due to a particular design. However, round section pipes are used as standard for the general transportation and processing of grain.

Round pipes can provide better grain flow, prevent grain from getting stuck or clogging in the pipe, and provide a smoother flow. Therefore, the preferred option for grain flow is usually round section pipes.