Washington State Ferries (WSF) is investigating the use of self-cleaning oil filtration systems with the hope of reducing environmental impacts and saving money. Researchers from Washington State University analyzed a system, installed on one ferry vessel, that does not use disposable filters and provides a higher particle removal efficiency than standard paper filtration, They examined the feasibility of using such a self-cleaning oil filtration system by looking at three key factors: filtration effectiveness, environmental impacts, and costs.
The researchers analyzed filtration effectiveness by using oil analysis records to review the values of oil properties known to be important for lubrication and that indicate oil degradation. Results showed little difference between the standard paper cartridge filtration system currently in wide use and the self-cleaning system. However, longer data collection periods with both systems at longer oil drain intervals would be needed to verify those results.
Environmental impacts were analyzed with a life cycle assessment methodology that quantifies potential impacts on the basis of expected operation. Although the self-cleaning system demonstrated fewer impacts from oil and filter use, the additional diesel fuel that the system consumed outweighed the benefits in many impact categories. For most of the environmental impact categories analyzed for both types of filtration systems, diesel fuel consumption for pumping oil dominated total system impacts.
A life cycle cost analysis suggested that the standard system would outperform the self-cleaning system in terms of 50-year life cost (unless the oil lifetime could be increased by more than three-fold), mostly because of the additional fuel use of the self-cleaning system. However, the filtration effectiveness analysis did not support a three-fold oil lifetime extension for either system.
On the basis of the analysis, decision makers at WSF elected to remove the pilot installation of the self-cleaning filtration system and currently have no other plans to implement such a system on other vessels in the fleet. Nevertheless, similar systems with different operational parameters or characteristics might perform differently, and the conclusions of this project are not meant to suggest that another self-cleaning or centrifugal filtration system would produce similar results. For example, a similar system that filtered oil only through a bypass (rather than full flow) might be able to reduce diesel fuel consumption, altering the results of the cost and environmental analyses.
Authors:
Quinn Langfitt
Liv Haselbach
WSU Department of Civil and Environmental Engineering
Sponsor: WSDOT
WSDOT Technical Monitor: Jon Peterson