(This Foreword is not part of ASME B29.18M-1993.)
The welded steel drag chains were developed to provide a series of steel chains similar to cast drag chains in the offset and combination types. Welded steel drag chains were originally introduced for the forest products industries and their ex- panded usage in recent years called for standardization of basic sizes.
In September 1967, a subcommittee of ANSI Sectional Committee B29 was ap- pointed with American Chain Association members from the engineering steel chain industry to develop a standard for welded steel chains, attachments and sprockets including the drag type. The Standard developed by this Committee affects only those dimensions that affect interchangeability.
To promote the use of this Standard in the international market, the metric equivalent of all dimensions is given. The American National Standards Institute approved this Standard in 1974. The 1981 revision included updating to the current ANSI Standards format and symbols covering chains and sprockets. Minimum Ultimate Strengths were reviewed and updated, where necessary.
The 1993 revision includes a modified definition of Minimum Ultimate Tensile Strength (para. 2.1). An optional barrel configuration was added to Table 1, and an optional wing configuration was added to Table 9. The American National Standards Institute approved ASME B29.18M-1993 on September 16, 1993.