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6C - Metalworking Fluid Management, Part II

January 01, 2013
M. Krishna
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2C: Control

The next “C” is Control, or the dashboard of the coolant management system. Many coolant manufacturers or service providers claim to provide coolant management service (CMS), but they focus solely on this part of the overall 6C concept. The “Control” section covers critical day-to-day activity that ensures the machine tool sump is monitored for coolant level, coolant concentration, and coolant pH.

Generally, water constitutes anywhere from 85-95% of end coolant, so monitoring water quality is equally critical.  However depending on the source reliability, the periodicity of monitoring the water quality can be customized.  The de-mineralized water or reverse osmosis water will give best coolant performance. I would argue that softening the water is not a good solution, as minerals are replaced rather than removed. 

Although controls are a lagging indicator, the trending of the plots are a real time indicator of issues or problems that could arise in the near future.  The success of this depends on the effectiveness of the training for those who are handling the measurement systems.

This “C” is only the beginning of coolant management service (CMS), but for many this is the end. It is up to the end user or the customer to ask their CMS providers to go beyond this “C” and complete the coolant management cycle.

3C: Contaminant

Most commonly, metalworking fluids fail due to contamination, or “unattended” contamination.  The two major contaminants are (floating) tramp oil, and metal chips and fines.  In a machine tool, tramp oil sources cannot be eliminated as they are critical to the machine tool, but they are also detrimental to coolant performance. Unfortunately, coolant is the indirect second-tier product in the supply chain, so coolant suppliers and their management teams have to live with this necessary evil.  It becomes economical to have a removal/reduction system for tramp oil, rather than trying to prevent or eliminate the contaminant. 

The tramp oil is one major root cause for coolant smell also known as “Monday morning odor”.  In layman’s terms, the presence of tramp oil layers prevent coolant aeration. The absence of oxygen causes bacteria growth, resulting in the foul smell from the coolant tank. So, planning for an effective tramp oil removal system is a must for a successful CMS.  

A wide variety of tramp oil and chip removal systems are available in the market and selection will depend on having a proper understanding of the coolant dynamics in the machine. 

Just as a guideline, belt and disc skimmers are recommended when the turbulence is very low in the tanks. The most critical part of the oil skimming system is the oil skimming belt. There are many assembly shops that make belt skimmers, but only a few make patented Oleophilic belts.  Different types of belts are available for coolant and cleaner applications.

When the tank is turbulent, you would use a different type of skimmer like a coalescer.  It is strongly suggested that the end user (in conjunction with the coolant manufacturer) determine the most suitable methodology for on-line contaminant control together prior to installation.  Once installed, the system can then be routinely maintained by any CMS provider.

The other contaminant, chips and fines are to be handled through a filtration mechanism that is often customized to the operation. Generally, the manufacturer will have this incorporated into the basic machine design during the process design stage.  Even if you have the best filtration system design, the daily management and handling of the filtration equipment along with it’s cleaning and maintenance schedules contribute to the system’s overall success.

The next installment of this article will appear in the April issue of the MWF newsletter, and will explore the next “C”: Cleanliness, including the handling of chips, fines, burr, sludge and effective tank cleaning systems. Click here to read Part I, III, or IV.

M. Krishna is the Managing Director at Master Chemicals India in Pune, India. You can reach him at mkrishna@masterchemicalindia.com.

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