Functional Unit for a lubrication system

Question

I'm trying to figure out the functional unit for a lubrication system that supplies lubricant at the rate of 600 litres per minute. The life cycle of the system is 15 years. The major components modelled are the motor, pump, reservoir, the lubricant and pipe connection. The reservoir capacity is 5000 litres. As I am new to LCA, I am not sure what to use as the functional unit and also I am a bit confused on which reference flow to be used for the functional unit. I am using ecoinvent 3.8 database.

Answer 1

Hi poobeshks,

you will find good overviews of function units for lubricants in the literature, e.g Bart, J. C. J., Gucciardi, E., & Cavallaro, S. (2013). Chapter 11: Environmental life-cycle assessment (LCA) of lubricants. In Biolubricants (pp. 527–564). Elsevier. https://doi.org/10.1533/9780857096326.527. Some examples are given here. It makes most sense if you take a functional unit that referes to the performance of the lubricants like: area of aluminium rolled, 1000 work pieces produced, volume of oil used to cut 1000 m³ of wood. Some LCAs also use 1 kg of oil, 1 m³ of hydraulic fluid, 1 kg of lubricant as FU. Hence, you will use the respective quantity as reference (can be mass/volume based of the lubricant or better the results of lubricating (area or wood cut).
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Comments

thanks. That's a nice reference. BTW, the lubricant is used in circulating system over a period of 20 years, will I have to designate the FU to be in flow rate or the total volume that is circulated in 20 years? say the quantity of lubricant in the entire system is 2000 litres at any given instant and the circulated quantity is 500 lpm, so throughout 20 years of lifetime, total lubricant circulated would be 4.7 billion litres. I'm a little confused on this. If you would, I'd like a clarification. Appreciate it!!