COLLARIN EJE 30mm. STD (ZN)

Function and technical context

The 30mm STD shaft collar with zinc protection is a subsea driveline component that hugs the tailshaft at the height of the hull or hub, acting as an axial stop and retaining element that prevents longitudinal displacement of the propeller shaft. It works in the propulsion system, at the interface between the shaft and the stuffing box or horn, collaborating with the shaft line bearings to maintain correct alignment during navigation. The zinc finish of the collar also fulfills a galvanic function of cathodic protection, defending the shaft and adjacent metal parts against electrolytic corrosion typical of the marine environment. If this component fails, degrades or is lost, the shaft can experience axial displacement under load, compromising propeller alignment, increasing vibrations and accelerating wear of the stuffing box and stern tube bearings.

When to replace this part?

The most common symptoms that indicate that the shaft collar needs to be checked or replaced are: unusual vibration transmitted to the hull during navigation, noticeable axial play in the propeller shaft when manually pushing and pulling it while the boat is dry, and visible wear or advanced corrosion of the collar itself or the integrated sacrificial zinc. As it is a cathodic protection element as well as a mechanical one, it is recommended to inspect the collar at each beaching or at least once a season, replacing it when the zinc shows wear greater than 50% or when cracks, looseness or loss of tightening in the shaft are noticed. Replacing the collar preventively at each annual tune-up is a low-cost measure that prevents progressive damage to the horn, the stuffing box and the shaft itself, repairs that can be very expensive in ocean navigation.