Coupling, Load Security, and a Trailer That Will Not Stay Put
You are picking up a loaded flatdeck at a lumber yard. The trailer has been dropped on level gravel with the landing gear down and the spring brakes set. When you back under it, the kingpin engages but the fifth-wheel jaws do not visibly close. You raise the landing gear, tug twice with the tractor in a low gear, and the trailer holds. You then notice the trailer has no wheel chocks and the gravel is loose. The load is bundled lumber with two steel straps over the bundles and no friction mat. The shipper says the straps are rated and the load has never moved. You are 90 km from the destination on a route with two 6 percent grades and a 20-minute stretch of rough pavement under repair.
1. What must you verify about the coupling before you accept the trailer, and what does the failed visual check mean?
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A tug test is necessary but not sufficient. You must physically look at the jaws from under the trailer to confirm they are closed around the kingpin, check that the release handle is fully in and latched, and confirm the safety latch is engaged. If the jaws do not visibly close, the coupling is not verified, and a tug that holds proves only that the kingpin is caught, not that the lock is seated. Back out, inspect the fifth wheel for a bent jaw, debris, or a mis-set lock, and re-couple. Also confirm the trailer apron sits flat on the fifth wheel with no gap, and that the air lines and electrical cord are connected and not chafed. On loose gravel with no chocks, the trailer can shift as you couple, so chock it or have someone hold it. Do not accept the unit until the lock is confirmed visually.
2. Assess the load securement for the route described and state what you would change.
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Two straps over bundled lumber is thin for a load that will see two 6 percent grades and rough pavement. The straps must be rated for the working load, in good condition, and tensioned correctly, and the aggregate working load limit must meet the requirement for the cargo weight. Rough pavement and grades produce fore-aft and lateral forces, and smooth steel strapping on smooth bundles can slip without friction material. Add friction mats or dunnage under the bundles, add more straps so the load is held at intervals along its length, and check that nothing can slide rearward on the downgrades. Verify the bundles are banded and that the bands are not the only restraint. Re-check tension after the first few kilometres, especially after the rough section, and log the securement check. If the shipper will not let you add securement, the load does not move.