Understanding Fifth Wheel Couplings

understanding fifth wheel couplings

There are several critical safety aspects to heavy vehicle combinations, one of which is couplings, and understanding fifth wheel couplings is vital to the safety and efficiency of a trucking fleet. Bob Woodward, Chief Engineer, Australian Trucking Association, explains some of the issues.

Too often fifth wheel couplings are taken for granted because of familiarity. However, if those critical safety items are functioning normally, and in accordance with requirements, regardless of what else may happen, the vehicle can be brought to a safe stop.

Mechanical couplings that connect vehicle units, prime mover to trailer, or trailer to trailer have been developed to facilitate interchangeability and accordingly, standards have been developed to ensure connectivity compatibility of the various coupling types.

The most common mechanical coupling used in multi-vehicle combinations is the fifth wheel and kingpin. But these are available in several sizes two inch, three inch and 3.5 inch, check the fifth wheel and the kingpin.

Coupling and uncoupling also varies from operation to operation, from once a month or once a week, to as much as eight times in a single day. The more often coupling and uncoupling occurs, the greater possibility of a critical aspect being overlooked.

To combat this and assist operators with their procedures, the ATA’s Industry Technical Council has developed the Fifth Wheel Coupling and Uncoupling Guidelines Technical Advisory Procedure (TAP).

The TAP is a set of guidelines that provides a consistent, clear and safe procedure for coupling and uncoupling prime movers and semi-trailers using fifth wheel couplings, and addresses several key factors including technical and safety considerations, visual inspections, and coupling and uncoupling procedure.

The TAP was created by an expert Industry Technical Council working group, before review by the ITC and approval from the ATA General Council. Developed by the industry, for the industry, the TAP was created to meet the needs of operators and fill the gaps in the vehicle standards.

Fifth wheels allow quick coupling and uncoupling of semi-trailers, provide articulation for the combination, and provide additional stability and support to the semi-trailer. Where a fifth wheel is specially designed to have a turntable base as an integral part, the term ‘fifth wheel assembly’ includes that turntable base, and does not include the skid plate and kingpin, which are parts of the semi-trailer.

All procedures demand consistency, following an uninterrupted routine with an understanding of the importance and relevance of each step, and it is recommended that only one person undertakes the coupling or uncoupling procedure to prevent missing critical steps. 

The Fifth Wheel Coupling and Uncoupling Guidelines TAP is now freely accessible on the ATA website, and designed to help those who unsure of technical interpretations, how to best meet their compliance requirements, or work as efficiently as possible.

Not only does the suite of ATA ITC Technical Advisory Procedures provide informative guidance and advice to industry members, companies also use the material to improve their current practices and for training purposes.

To view the Fifth Wheel Coupling and Uncoupling Guidelines TAP, go to the this website, or to find out more about the Industry Technical Council.

understanding fifth wheel couplings