Biodegradable lubricants under scrutiny after reported failures


Thordon Bearings welcomed an industry initiative to evaluate the effect of biodegradable lubricants on sterntube bearings, after a reported increase in sealed oil lubricated propeller shaft bearing failures.
Many operators consider environmentally acceptable lubricants (EAL) a cure to meeting environmental regulations, particularly in waters where the US Environmental Protection Agency (EPA) has regulated the use of mineral oils. However, their performance as a propeller shaft having lubricant has come under scrutiny.

It is believed that some EALs may obstruct bearing and seal performance, damaging critical components and compromising oil-tight integrity.

Terry McGowan, President and CEO of Thordon Bearings suggests that the US EPA has contributed to this confusion by determining that four major types of lubricants can meet all the necessary required criteria to be classified as an approved EAL:

1.Vegetable oils
2.Synthetic esters,
3.Polyethylene glycols (PAGs),

However, not all of these EALs perform in the same way. The International Marine Contractors Association had warned that “choosing the correct type of lubricant for a particular application can be problematic, because most types offer some degree of biodegradability, but differ in performance and regulatory compliance”.

While these environmentally-friendly lubricants can cost significantly more than mineral oil-based products.the real concern is when biodegradable oils mix with water. Their viscosity can deteriorate with water ingress, resulting in reduced lubricating capacity and potential damage to seals and bearings. One easy solution for newbuildings is to use an open seawater lubricated system, eliminating these EAL issues entirely and saving the ship owner money,

said Mr. McGowan.

Speaking about the 1999 large canola oil spill in Vancouver harbour, Canada, which had as a result many seabirds to be killed, Craig Carter, Thordon’s Director of Marketing, mentioned that EALs were developed to protect the marine environment from oil-based pollution. However, that does not mean that they are environmentally safe to marine species.

We issued a statement in 2015 calling for more research on biodegradable lubricants regarding their operational and environmental performance, so are pleased to hear there is now a concerted effort to provide shipowners and operators with the information they need to make better informed lubricant decisions,

Mr. Carter concluded.