What is Tramp Oil?

Tramp oil is a term that describes any unwanted hydrocarbon-based substance that contaminates machine coolant. This issue occurs mostly metalworking and manufacturing industries. Tramp oils can lead to numerous problems that affect work environment safety, production efficiency, and the cost control abilities.

tramp oil buildup in coolant tank


The Unwanted Wanderers of the Machining World

The word “tramp” can have a few different meanings. One of the earliest definitions was that of an unwanted homeless wanderer. Similarly, in the machining world, tramp oil is a term for any unwanted hydrocarbon-based substance that migrates into the coolant of a machining center.

cnc machine coolant tank

These oils can lead to numerous problems that affect the safety of the work environment, production efficiency, and the ability to control costs.

What Causes Tramp Oil?

How do these hydrocarbon-based substances find their way into a coolant sump?

There are a few different avenues.

Machining centers employ various linear motion and rotary motion components such as bearings, slides, ball screws, and spindles that require lubrication to function efficiently. Over time, these lubricants can find their way to the machining center platform where they mix with cutting fluid or coolant.

Another source of contamination is from the materials being processed in the machining center. Most stock metals have a corrosion prevention coating which is typically oil based. If the oil based coating is not removed prior to machining, it will end up mixing with the coolant.

Problems Associated with Tramp Oils

Tramp oil contaminated coolant causes a variety of problems if not separated and removed.

cnc router bit with coolant spray

First, the coolant’s performance ability suffers. This is because oil in coolant reduces the coolant fluid’s ability to reduce temperatures effectively. Any oil that is present in the cutting fluid will promote heat generated by the tool, which can shorten tool life considerably.

Another consequence of oil coming in contact with a hot cutting tool is smoke. At high temperatures, the oil can become hot enough to burn. This can create unsafe working conditions.

When left alone, tramp oils that settle in coolant become breeding grounds for anaerobic bacteria. The oil essentially prevents oxygen from mixing with the coolant, which can promote the growth of anaerobic bacteria. Workers who come in contact with these bacteria are susceptible to contact dermatitis. The bacteria can also generate hydrogen sulfide gas, which emits an unpleasant rotten egg odor.

tramp oils in machine coolant sump

Removal & Separation Solutions

There are two common methods for removing tramp oils from coolant. These are coalescers and oil skimmers.

belt oil skimmeroil boss tramp oil separator

Coalescers consolidate small oil particles into larger droplets. Filters or baffles are then gather larger droplets for removal. Coalescers are a good option for larger area applications as they have greater collection area than skimmers.

Skimmers utilize the differing specific gravities between oil and coolant/water to remove tramp oils. A motor driven belt that is typically constructed of an oleophilic, or oil attractant material, is placed into a coolant sump or reservoir. As the belt moves through the coolant, it attracts tramp oils. The oil is scraped off by a wiper and deposited into a container.

The relative simplicity of skimmers lends to their tremendous versatility. They can be used in a variety of applications and are better suited for extreme applications. This is because skimmers, unlike coalescers, do not use pumps, which can become clogged with shavings or other solids.

Benefit of Removing Oil from Coolant

Removing tramp oils has multiple benefits that cannot be understated.

First and foremost, it is easier to maintain a safe work environment that is free of oil laden smoke or harmful bacteria.

Secondly, clean coolant will work more effectively and promote higher production efficiencies. This allows tools to run at peak operating speed, promotes greater consistency, and improved quality.

Finally, removing tramp oil from coolant can produce significant cost savings. Tools that operate within their design parameters and do not overheat will have a longer life.

It is possible to recycle “clean” coolant, unlike oil contaminated coolant, which requires proper disposal in accordance with environmental regulations. Abiding by these additional regulations costs money.

The proactive and sensible approach to dealing with tramp oils is to reduce or eliminate their impact in your facility before they cause problems. This will promote a safer, more efficient, and most conscious operation.

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