Six Sigma – Monitoring Variables in Cleaning – Part 2

Here are a few more variables that can be monitored in cleaning systems in pursuit of a Six Sigma process –

Oil laden detergent –

A good oil removal system is paramount in controlling the quality of the detergent in a cleaning system.  An oily bath can quickly become ineffective in removing additional oil and even particulate from the parts.  Several options are available for continuous removal of oil from a cleaning system.  A simple oil coalescer may be sufficient in maintaining the bath of some machines but a more sophisticated ultra-filtration system may be required to maintain the effectiveness of the detergent by controlling the oil level in other,  usually more critical, applications.

Note – Realizing that I haven’t yet talked about oil removal in the blog, I will address both oil coalescers and ultrafiltration in soon to be published blogs.  Check back if you are looking for more information on either of these oil removal methods. – FJF

When selecting an oil removal system test the oil to see how it reacts in the oil removal system.  For a coalescer to function effectively the oil must float to the surface of the cleaning solution so that it can be easily skimmed off.   For an ultra-filtration system the membrane must be able to discriminate between detergent and oil and oil and/or detergent must not clog the pores of the membrane.

An ultra-filtration would be beneficial to achieving six sigma cleaning because it will remove the oil and particulate down to .5 micron. Thus keeping the wash or rinse in like-new conditions for months.  By eliminating the variances of the detergent cleanness the probability of meeting the cleaning specification is greatly increased. Ultra-filtration can also pay for itself by eliminating machine downtime due to frequent dumping of detergent.

Temperature –

The system should have a digital temperature control system to maintain the temperature.  The control should have the ability to both control the source of heat and report its readings to a remote device to produce an alarm in the event a significant deviation from the desired temperature is detected.  Redundant temperature sensors help to insure proper temperature control and should be considered.  In most cases, electric heat is easier to control and maintain and is recommended.  Steam heat is more difficult to control and is especially prone to being out of range and should be avoided.

Dirty Filters –

Filters are a critical factor in most cleaning systems.  As filters blind off due to the collection of particles from the cleaning solution, the flow slows to the detriment of the cleaning process.  Means to monitor and indicate that filters are operating effectively or are approaching the end of their life are an important part of process monitoring.  Notification of the need for filter replacement or maintenance should come with enough advance notice to allow the required action to be initiated while the machine is still meeting specifications.

One obstacle to changing the bag filters when needed is that the machine must be taken out of service to change the filter.  This can cause the operator to choose between production and part quality — production wins every time.  A dual filter option could be added so the filter canisters can be switched from one to another while the machine is running.

Further information on monitoring filters is available at Sorting Out Filters – Plumbing Options and Tips and Sorting out Filters – Monitoring Filter Health.

In the next blog we will explore even more process variables that can be monitored to help achieve Six Sigma performance.

–  FJF –