In fall protection, the dorsal (back) D-ring is the single most critical load-bearing component. It is the attachment point where the lanyard hooks to the harness, and in the event of a fall, it bears the entire dynamic shock load of the worker's body. Workers routinely inspect the webbing of their harness for cuts and burns, but they almost never inspect the D-ring itself, assuming that forged steel is indestructible. This assumption is fatal.
D-rings are subject to violent, cyclical metal fatigue and severe mechanical abuse. Every time a worker leans back in a harness, adjusts their lanyard, or accidentally strikes the D-ring against a steel beam, the metal is stressed. Furthermore, the D-ring rotates within its webbing loop, grinding against the metal grommet or the forged insert. This constant friction creates metal wear grooves.
Over time, the once-rounded cross-section of the D-ring wears down to a razor-sharp edge on the sides. This is a two-fold catastrophe. First, the thinning of the metal drastically reduces the tensile strength of the ring; it can shear apart under the 3,000 to 5,000 pounds of force generated in a fall. Second, if the ring is sharp, it acts like a blade. In a fall arrest, the violently deploying shock pack can snap against the sharpened D-ring, severing the lanyard webbing, dropping the worker to their death.
You must physically grab and manipulate the D-ring during your pre-use inspection. Run your thumb around the inside curve of the ring. If you feel a lip, a groove, or a sharp edge, the harness must be immediately destroyed. Also, grab the ring and attempt to wiggle it within its webbing loop. If the grommet is popping out, or the webbing is torn around the insert, the ring will twist and side-load in a fall, causing the connector to fail. Never paint a D-ring; paint hides the stress cracks and wear grooves. If the ring is gouged, the harness is dead.
