Loop ’d Loop

Article From: Products Finishing,

Posted on: 6/1/2002

Amusement park ride or industrial process?

Amusement park ride or industrial process? It could be a wild ride in an industrial process. We are, in this case, referring to closed loop compound systems for mass finishing. If done right, it will not be a wild ride for you.

Closed loop mass finishing systems can be a good thing. Correction! Make that should be a good thing. The effluent from the most popular burr, edge, and surface finishing process can be reduced to zero. The use of compounds is considerably reduced. Flow rates can be optimized for each process without regard to waste. Those are good things.

The bad thing is that too large a percentage of closed loop owners are very disappointed with the results. Some of the unexpected, bad things they received included less than projected savings, bacteria problems, increased cycle times, corrosion problems, inordinate labor consumption, production downtime, dermatitis, and an assortment of other disappointments.

In preparation for an article that appeared in 1992, I visited four operating closed loop installations, each using a different approach in terms of equipment and method. Each was a typical vibratory finishing application using either ceramic or plastic media. The capital costs ranged from under $10,000 to over $100,000. Within five years each of those systems was scrapped. The good news is that an increasing number of good experiences are now occurring, and the industry can realistically expect more and more successful installations as buyers and vendors become more acquainted with the realities of these systems.

The beginning of a good system occurs when management is given an honest expectation of the investment and savings involved. Unrealistic promises are too often made regarding the reduction in compound dollars. When the actual reductions then fall short of the goal, and new costs are added, trouble begins. It is also tempting is to accept the “cheaper is better” mentality when contemplating capital purchases. Low bidders prey on these temptations, and the result can be that you save yourself into a costly disaster.

Let’s consider, first off, what the compound savings realistically might be. Do you know that a typical vibratory finishing machine will evaporate about 0.2 gallons/cubic foot, per hour? A twenty cubic foot vibrator —a common size in manufacturing—will evaporate about 4 gallons of solution every hour. In this case, if the flow rate into the machine is 20 gallons/hour, you are losing 20% to evaporation. In addition, depending on the time cycle and some other variables, carryout on the parts and losses from the handling system can account for another 5 to 10%. Those losses cannot be saved with a closed loop system.

Next, consider that with a flow-through compound method you might be mixing your compound at about 1.25%. This provides the cleaning, rust inhibiting, and other qualities you need for your process. The cleaners, inhibitors, water conditioners, bacteria stabilizers, and other ingredients of the compound are, however, depleted with each use. To make up for this, a closed loop system will usually be set up at 5% to 10% concentration. So, the fewer gallons you use will be more expensive gallons. Most systems will have to be emptied, cleaned up, and re-charged about once a year. The cost of the compound lost and possible hauling charges deduct from your savings.

Consider, also, the additional compounds and items that might be required by the new system. These may include flocculating agents, filters, filter cleaners, anti-foam agents, bactericides, titration, or other testing chemicals and kits. Of course, someone will have to be trained to use all these things, and to provide whatever new maintenance or services will be required. The person, or persons, assigned these tasks will sometimes be on a higher pay scale than those who were previously assigned to mass finishing.

In effluent management there is jocular saying that “dilution is the solution.” Consider that some of the effluent from other operations, such as janitorial operations, may contain high concentrations of oils, phosphates, ammonia, or other chemicals that should be within certain limits. These effluents were considerably diluted with the mass finishing effluent before you installed a closed loop system. How will your plant effluent measure after the change? Some companies are also using their closed loop systems to service the janitorial needs.

Avoiding the pitfalls and installing a good system pays great dividends. There will be savings, the regulators will be happy, and you will be helping the environment. On the other hand, it could be a wild ride. With good planning, the choice is yours.

 

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