Editing Cutting fluid (section)

==Degradation, replacement, and disposal==
{{Anchor|Tramp oil}}
Cutting fluids degrade over time due to contaminants entering the lubrication system. A common type of degradation is the formation of ''tramp oil'', also known as ''sump oil'', which is unwanted oil that has mixed with cutting fluid.<ref name="Smid2010p114">{{Harvnb|Smid|2010|p=114}}.</ref> It originates as [[lubrication]] oil that seeps out from the [[slideway]]s and washes into the coolant mixture, as the protective film with which a steel supplier coats [[bar stock]] to prevent rusting, or as [[hydraulic fluid|hydraulic]] oil leaks. In extreme cases it can be seen as a film or skin on the surface of the coolant or as floating drops of oil.

[[Skimmer (machine)|Skimmer]]s are used to separate the tramp oil from the coolant. These are typically slowly rotating vertical discs that are partially submerged below the coolant level in the main reservoir. As the disc rotates the tramp oil clings to each side of the disc to be scraped off by two wipers, before the disc passes back through the coolant. The wipers are in the form of a channel that then redirects the tramp oil to a container where it is collected for disposal. Floating [[weir]] skimmers are also used in these situations where temperature or the amount of oil on the water becomes excessive.

Since the introduction of CNC additives, the tramp oil in these systems can be managed more effectively through a continuous separation effect. The tramp oil accumulation separates from the aqueous or oil based coolant and can be easily removed with an absorbent.

Old, used cutting fluid must be disposed of when it is fetid or chemically degraded and has lost its usefulness. As with used motor oil or other wastes, its impact on the environment should be mitigated. Legislation and regulation specify how this mitigation should be achieved. Modern cutting fluid disposal involves techniques such as [[ultrafiltration]] using polymeric or ceramic membranes which concentrates the suspended and emulsified oil phase.

[[Swarf|Chip]] handling and coolant management are interrelated. Over the decades they have been improved, to the point that many metalworking operations now use engineered solutions for the overall cycle of collecting, separating, and recycling both chips and coolant. For example, the chips are graded by size and type, tramp metals (such as bolts and scrap parts) are separated out, the coolant is centrifuged off the chips (which are then dried for further handling), and so on.<ref name="Willcutt">{{Citation |last=Willcutt_2015-06-18 |first=Russ |date=2015-06-18 |title=When the chips are down |journal=[[Modern Machine Shop]] |url=http://www.mmsonline.com/blog/post/when-the-chips-are-down |postscript=.}}</ref>