There is no European or 'International' association that issues screw conveyor guidelines or standards. The basic problem of international reconciliation is that the US is still on Imperial sizes whilst most of the rest of the world is metric.

CEMA has done a great job of consolidating US standards for screw conveyors and their components, although these designs are a bit long in the tooth and tend to stultify developments and designs for special applications. It should be remembered that CEMA is an association of conveyor equipment manufacturers, so they will have no driving commercial or technical motivation to change, to bring dimensions in line with metric or 'outside' international standards.

In UK, SHAPA, (Solids Handling and Processing Association) has not addressed the issue, as the main dimensions of screw conveyors are covered in British Standard BS 4409 Part 1 and 2. Components are not included in the same manner as CEMA, as most manufacturers make to individual design. This allows more flexibility to meet variable duties. The market is divided into off-the-shelf items that are used for simple applications and dedicated designs that tend to be applied to applications that call for careful performance evaluation, where reliability of function outweighs marginal capital cost.

The answer to you query would appear to depend upon the site of use for the equipment. If within a US zone of influence the CEMA standards are most appropriate, otherwise ISO dimensioned equipment should be specified. In either case it would be prudent to note that International safety considerations for screw conveyors come under the recently reviewed EN 618 - 'Continuous handling equipment and systems, Safety and EMC requirements for mechanical handling of bulk materials except fixed belt conveyors'. Associated feed hoppers come within EN 617.

FEM 2 581:11.1991 usefully lists the 'Properties of Bulk materials' and FEM 2 582:11.1991 describes the 'General properties of bulk materials and their symbolisation'.

Lyn Bates ■