Thordon Bearings has indicated that a polymer propeller shaft bearing that is lubricated by seawater could generate significantly less underwater radiated noise (URN) than oil-lubricated metal bearings.
Seawater-lubricated polymer bearings are less noisy than metal ones but also quieter than rubber bearings and staves, according to the Canadian polymer bearings specialist.
“A common problem with conventional rubber bearings is the squeaking and squealing that can occur when trawling at low speeds,” explains Gary Ren, Thordon’s chief research engineer.
“This high-pitched noise will reverberate for miles underwater, but the friction associated with conventional bearings could be removed with an elastomeric polymer bearing system, meaning shafts turn more easily,” he adds. “Noise is absorbed by the bearing in the 20- to 200-rpm range.”
The findings have been verified by New Zealand-based distribution and engineering partner, Henley Group, which has fitted Thordon bearings to some of the world’s largest all-carbon vessels.