The cleanliness requirement of the sump is the most obvious and known factor but is the least attended to. The main reason being that, any sort of proper cleaning of a sump will need the machine tool to be down for a considerable amount of time. In most cases, the production function overrules the maintenance function and hence available time for a proper cleaning is always a constraint. In today’s scenario of fluid economy, varying demand structures and heavy pressure on cost, even dedicated shutdown times for maintenance is taking a toll.
Added to this - the machine tool designers often overlook the necessity for a good assessable sump-design for cleaning. With due respect to designers, in many cases the coolant sump is a “design filler” and takes all sorts of geometry to finish the machine tool. This makes the coolant sump even more difficult to be assessed by human hand in a normal course for cleaning activity.
Knowing the two major constraints as listed above, and also knowing that these cannot be resolved (in existing machine tools at least) we need to come up with a work-around solution. Most likely, the machine tool designers and production managers who read this article will try and resolve these issues to provide some relief to the maintenance personnel.
To have an effective cleaning process within time constraints, the work around solution is the use of “sump cleaners”. Sump cleaners today are capable enough to clean machine tool sump with ZERO DOWNTIME. Sump cleaners use an innovative suction method called “indirect suction” meaning the dirty coolant is sucked out of the machine sump without touching the pump. They can suck out anything in the coolant tank that will fit into its suction hose (which is generally 2”). The dirty coolant with sludge/chips/fines/debris is sucked directly into a 50 micron filter sleeve and the filtered coolant is stored in the tank. Then, this filtered coolant can be discharged back into the machine coolant sump. The indirect suction method also ensures the pump system is maintenance free. With suction speed close to 300LPM, the rate of cleaning achieved is very high.
There is also an automatic version of this “sump cleaner” that cycles the coolant (suction of the dirty coolant, filtration, then discharge of the filtered coolant back into machine tool sump) “on-line”. This means the suction/discharge cycle takes place when the machine tool is running. The coolant cleaning happens with ZERO DOWNTIME of the machine tool. This cycle is programmable through a PLC that is flexible to handle any size of machine tool sump. This type of cleaning is termed as “flush-cleaning” with repeated charge / discharge cycles.
The automation system of a well-known brand is capable to handle a 1000 Liter sump cleaning anywhere between 20-30 minutes. The manual method would normally need over 4-5 hours. This way, good cleanliness can be achieved with solid ROI.
The earlier sections dealt with the efficiency of the cleaning system. This section deals with effectiveness of the cleaning system. It’s not just good cleaning that is essential, but a sustained commitment to a cleaning schedule that ensures cleanliness of the sump in an ongoing manner. This scheduling could be a part of the preventive maintenance (PM) or condition monitoring (CM) schedules.
This commitment is usually driven by the top within an organization. Thus “cleanliness” as an activity is only as effective as when you have a commitment from management. This could be implemented through TPM.
It is a known fact that what is not measured cannot be controlled. Hence we need a good measurement system for good monitoring and control of the cleaning process. You can measure the effectiveness of your program by looking at coolant life expectancy. You’d look to increase it from its current level to a minimum of 40-50% higher life expectancy when you implement a program.
Even if you have a strategy, it’s absence of execution that can kill all your work on the strategy. Hence commitment is a “C” that you cannot compromise in the whole 6C system of MWF management. Click here to read Part I, II, or IV of this series.
M. Krishna is the Managing Director at Master Chemicals India in Pune, India. You can reach him at firstname.lastname@example.org.
Other articles from this issue: