Case study - machine coolant tramp oil


Courtesy of SkimTech Inc.


Midwestern Manufacturer of metal stampings and machined parts for the Automotive Industry.

The Problem:

Tramp Oil collecting in metal working coolant.  Oil concentration levels raise to unacceptably high levels, adversely effects product quality and promotes bacterial growth which leads to worker skin disorders.  Cutting tools leave burn marks on the parts due to high oil levels, which is a perceived quality problem with the end user.    

Primary Cause:

Lubricating oil and grease “Tramp Oil” leaking from metal working machine(s) into cutting tool and stamping water cooling system.  
Metal used in machining operations have protective oil coating that washes off the stock during machining by cooling system.
Tramp oil collects in coolant reservoir and forms a surface layer that promotes bacterial growth.

Secondary Cause:

The existing “Belt Skimmers” continually reintroduced free-floating tramp oil into the coolant by dragging the floating waste oil back into the coolant.  The tramp oil dragged into the coolant increases oil concentration levels and is drawn back into the machine by the coolant pumps.  Tramp oil comes into regular contact with operator’s hands.
The Existing “Disk Skimmers” also continually reintroduced the free-floating tramp oil into the coolant where it was reintroduced to the machine and onto the operator’s hands.

The Solution:

  1. Eliminate the use of the Belt and Disk Skimmers.
  2. Plumb two of the three machining cells to a central coolant reservoir and circulation system.  Coolant reservoir includes a settling tank large enough to contain the coolant long enough to allow an average sized droplet of oil to raise to the surface of the coolant.
  3. Install one SkimTech Model BG34 Oil Skimmer with 60” Angle Frame Mount to continually remove the tramp oil without dragging the tramp oil back into the coolant reservoir.
  4. Install one SkimTech Model AG25 Oil Skimmer on each machine where it is not practical to use a central coolant system.  Enlarge the reservoir tank to allow more settling time for the tramp oil to rise to the surface of the coolant where it can be skimmed in a more efficient manner.  The Model AG25 Oil Skimmer does not reintroduce the tramp oil back into the coolant.
  5. Installing the Tube Type Oil Skimmers minimized the concentration of tramp oil in the coolant which significantly reduced bacterial growth.  Tube Type skimmers use a floating collector tube that is driven in a continuous loop by the skimmer and does not reintroduce the tramp oil back into the coolant flow.
  6. The customer also experimented with expensive synthetic and other mixes of coolant.  After addressing the real problems with the tramp oil concentration levels – dwell time to allow the tramp oil to float to the coolant surface, and eliminating the use of the belt and disk skimmers, the customer was able to continue using their lower cost oil/water coolant mix without continued quality and worker health related problems.

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