Tribological Testing of Environmentally Acceptable Lubricants for Maritime Applications
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In marine applications, such as ship stabilizers, manoeuvring or propulsion systems, a number of mechanical components are situated below the waterline. Due to negative effects of lubricant leakage in marine environments, new regulations are forcing the industry to increase the use of environmentally acceptable lubricants (EAL). This project studied the effect of an EAL on the tribological performance of sealing systems compared with a mineral oil. Pure PTFE, carbon added PTFE and UHMWPE was tested against NiAl bronze and WC coated steel in both lubricants. The presence of abrasive particles and water was investigated. A number of tribological tests were performed on a reciprocating tribometer (TE88) in order to compare seal materials and lubricants. Coefficient of friction (CoF) and wear were studied and revealed the following: PTFE shows in general lower CoF and higher wear than UHMWPE when testing without abrasive particles, and vice versa with abrasive particles. Modified PTFE performs better than pure PTFE in tests with abrasive particles. Coated steel shows less wear than NiAl bronze, especially in tests with abrasive particles. All polymers show higher wear sliding against coated steel than NiAl bronze, but vice versa with abrasive particles. Despite having higher friction, UHMWPE is an excellent choice as a seal material in these applications because of slightly lower cost and lower wear on pins and plates, especially with the presence of abrasive particles. This particular EAL performs similar to the mineral oil regarding wear and better regarding CoF, especially with the presence of abrasive particles. When there is a possibility for abrasive particles in a sealing system with these conditions, the use of UHMWPE against coated steel in EAL is an obvious choice for achieving lower CoF and better wear resistance.