You can choose the wrong process. You can choose the wrong chemical. You can choose the wrong equipment. The purpose of my Cleaning Times column is to help you make none of those mistakes. Of those three mistakes, the most significant is to choose, and have your company pay for, the wrong equipment.

Stuff Happened

Some examples around my experience are that:

  • Often my consulting business involves trying to make a spray booth work like an immersion bath, or the reverse. It really can’t be done. No client wants to hear that!
  • A client bought an aqueous belt conveyor machine to clean parts that must be tumbled so all sides are exposed to cleaning action. You can’t do that with a belt conveyor.
  • Another past client needed help in rebuilding a set of wash tanks to allow for soil removal. They never considered what happened to the soil once it was liberated from their parts. Their tanks were full of soil.
  • Another client wanted help to dry a hydrocarbon-based cleaning agent from cleaned parts. The cleaning was well done. But the drying equipment was designed to evaporate water not evaporate a high-boiling material. The parts appeared soaked with oil.
  • Another client was trying to rinse parts by immersing them in a water bath. The parts were held in a nonporous basket that had been used to store parts—not rinse them. It had around 25% open area. That inexpensive basket didn’t allow adequate circulation of the rinse fluid through the parts. Rinsing was poor, but it improved when a basket with around 60% open area was used.
  • A supplier told me “…I lost a sale of an inline to a rotating table batch washer. The customer’s justification was price and quality: ‘$15,000 vs. $75,000, and it cleans just as well.’ However, after installation, the customer soon realized that cleaning ‘just as well’ applied to one part. After one or two parts, the small size sump was spent, full of soil, and had to be cleaned out.”

Common Denominator

The thread connecting all of these situations is that the user didn’t understand how cleaning was done. So they bought equipment ill-suited to their job. An understanding of the principles affecting cleaning work is the secret to avoiding an unpleasant visit with your boss.

Suppliers—Are They to Blame for Failure?

Suppliers can contribute to a poorly completed application. Their representatives can and do sell you equipment that is not well-suited to meeting your cleaning needs. That has happened, does happen, and will happen. But they aren’t responsible for most application failures where the wrong equipment is used.
This is because they, generally, have too much at stake to deceive you by misrepresenting the capabilities of their equipment and the principles underlying its design. The business plan of suppliers is to prosper over the long-term, and intentionally selling users equipment (or cleaning chemicals) ill-suited for their application is not likely to be a component of that strategy.

A Management Approach

A philosophy of management I have used successfully is to make sure everyone knows their role, their goal, and who is empowered to make a decision (and who is not). This approach is known as “roles, goals, and whose got the ‘D’.” In the purchase of cleaning equipment:

  • Your role as a consumer/purchaser is to understand what you need and how what you purchase will fulfill those needs. You are nearly certain to make the wrong choice of equipment if you can’t do this. And today that can lead to finding another career opportunity by visiting
  • Your goal is make the cleaning difficulty disappear via selection and implementation of the appropriate cleaning process (and procedures). Since most firms see cleaning as a value-subtracted operation, and not one that adds value, you may not be perceived as adding value to your organization when you are often noticed to gaze into the cleaning machine.
  • The role of the supplier’s representative is to inform you of how offerings they represent can meet those needs, in a competitive environment. If you ask the right question, a supplier will give you the correct answer to it. But, if you don’t ask necessary and pertinent questions, they won’t get answered. The normal supplier’s representative treads a narrow path. On one side there is failure because of misapplication. On the other side is failure to feed their family.
  • The goal of the supplier’s representative is to get paid via selling and installing equipment, which they can use as a reference when their family needs additional food. They can’t do that by selling you a lemon.
  • It is you who has the decision. Don’t leave it in the possession of your boss, the financial controller, the supplier’s representative, or anyone else. You are responsible for the success of the application. It is you who will be held responsible if it is not successful. You make the decision. This column is a resource to help you do that.

A Key Principle—Forget Selling Price

There are two reasons for this. First, the market for cleaning equipment is highly competitive—on a national basis. There are few large suppliers. Most firms manufacturing and selling equipment are small. They don’t have the financial muscle to manipulate prices. Very occasionally, one of the few large suppliers will try to “buy an application” via offering a factory-sponsored price that can’t be matched by other firms. But, don’t wait for this event.

Second, the cost of your failure is usually much more significant than the price of your success. Poor cleaning performance causes product quality to be poor. This usually leads to lost business, production shutdowns, unsold inventory, or political disruption. Granted these items show only indirectly on an area cost sheet. But you can be sure that their impact can be easily located on a business balance report. In summary, pay the right price to buy the right equipment for the job.

And Yet…

Don’t expect prices for similarly designed immersion or spray parts washer to be the same among suppliers. Suppliers differentiate their offerings by providing different features, quality, support, or warranty. All require a cost to the supplier. You will pay different amounts for a machine if you choose to value these items. And likely, you should do so.

Since most supplier firms are small and without financial muscle they may seek to differentiate their offering from that of the competition. They’ll offer better quality at a higher price or less quality at a lower price. Some examples are:

  • A pump with magnetic seals may last longer or leak less. But it will cost more for the supplier to purchase and install than a pump with graphite-packed seals.
  • A blower with less volumetric air throughput, or a heater with a lower wattage, can substantially change the price of a parts dryer. Can your production quotas and quality specification be met at that price?
  • Stainless steel skins (outside covers) make a great impression. But they add cost vs. glossy painted metal. A 2B finish to stainless steel skins looks even better, but isn’t cheaper.
  • Speaking of stainless steel, polypropylene tanks may do the job just as well—though they don’t appear as fashionable.
  • Tanks with cove corners are easier to flush (they trap less undrained liquid), but they cost significantly more to manufacture.
  • Computer-controlled ultrasonics cost more than do those started by a switch.
  • Automated handling of materials can double or triple the price of a cleaning machine vs. one requiring more human participation.
  • Prices for cleaning machines do vary because what is offered in return for them varies. Make sure you get what you need, and only that.

Anatomy of a Cleaning Machine 

When you purchase cleaning equipment, boxed machinery will arrive on your loading dock. What you have really purchased is at least four items: a design, the components used in the design, assembly of the components to complete the design, and support during your use. This is true whether you purchase an automobile, video game, or cleaning machine.

You can’t separate these four items. You can’t choose a cleaning machine with a brand of pump you use at your site, and a design of parts racks you have found useful, and the longest warranty, and workmanship equivalent to that done at your site. If you did choose all those items, you couldn’t afford the custom machine that would be the outcome.

The persons who market (not sell) each cleaning machine make conscious decisions about these four items to maximize their profit. They have (or should have) targeted a type of customer with certain needs and values. You make the best choice of machine when you recognize what are your needs and values, and select a supplier of machines who aims to meet them. Choice among the four items depends on you. In general, I rank the four items in this order of importance: design, support, components, and workmanship. On a scale of 1 to 10, design and support are 10s, components are a 3, and workmanship is a 2.

The Fallacy of Cleaning Tests

A standard sales tactic is “…let us test your parts and see if we can clean them…”. Having been on all three sides of this tactic—supplier, customer, and consultant—has led to one of Durkee’s Rules About Cleaning:

No supplier has ever returned dirty parts (at least deliberately) to a client after a cleaning test.

Cleaning tests are a huge sales cost for suppliers—a sizable commitment of equipment and manpower—and their impact on sales price is certain.

There are two problems with traditional cleaning tests:

  • They are not definitive. Often this is the fault of the user—they send only one (literally) part, or a handful of parts. A supplier can’t develop and confirm a process using that small number of parts. Alternately, if you send a keg, crate, case, or boxcar of parts, the supplier probably doesn’t have the time and resources to test that number. Suppliers aren’t in the business to develop processes and test them for every customer at that level of volume. Further, the effectiveness of these tests is self-limiting. The offer to test is made, in good faith, to nearly every customer. A free test is hard to decline. Nearly all users accept it. Suppliers then have to test for a number of potential customers for every sale, because they get only a fraction of the orders on which they quote. But the cost of all those tests is incorporated into the price you pay for your unit.
  • Something you may value more than cleanliness is not tested. That is throughput. The reasons are above. A legitimate measure of productivity requires a significant amount of parts, time, and commitment—whose cost can’t be justified by the supplier for every sales opportunity. The outcome is usually that the sales-related cleaning tests produce cleaned and returned parts. But they may not produce all the information about the application that is needed to support design, completion, and operation of a cleaning machine—to the level of quality and productivity required by the user.

Another Way

I advise clients to adopt another strategy—don’t accept the free cleaning tests. Buy the test you want. Screen suppliers and choose one with whom you are fairly certain you want to work.

Offer them $1,000 to do a test. Require them to use enough parts to establish that their proposed cleaning machine will meet your stated cleanliness standards and productive requirements. Witness that test.

The money that you spend will be returned to you as increased certainty about having chosen the right equipment (and supplier) to meet your needs. You’ll get more than $1,000 of the attention of your chosen supplier—they’ll know you are serious and likely to buy from them if they can demonstrate that they can meet your two needs. Accounting for overall project cost will show the $1,000 to be an item of inconsiderable financial consequence. But if the cleaning equipment fulfills your cleanliness and productivity requirements, it will be of practical consequence to your business.

Ten Principles for Successful Cleaning

There is not a short list here because I am not smart enough to distill collective experience into a few “secret words.” Each of these principles could be covered (and may well be or has been) in a separate column.


  1. Get those who do the work involved in the selection process. Your operator or shop foreman understands your cleaning situation and needs. Listen to them. But make your own decision.
  2. Both aqueous and solvent cleaning processes can be made to clean your parts. You’ll probably make your choice between them based on factors other than expected part cleanliness.
  3. Winnow your choices to one or two suppliers using published information and referrals. Then witness a cleaning trial by the supplier you most prefer. Don’t waste your time in the selection process (please see above). Spend your time making that selection work well.
  4. Define the quality of cleanliness (and dryness) you need. Do this by understanding what will be next done with the cleaned parts. Insist on finding some cleanliness test that quantitatively mimics that next step. Use the test in a statistically sound way.
  5. Take the time to understand how your cleaning machine manages the process of soil transportation. Cleaning is nothing but moving soil from where it isn’t wanted (on your parts) to where it should be (a dumpster, recycle tank, etc.). It is usually no trick to get soil off parts. The magic is needed to get soil out of the cleaning bath, out of the rinse bath, not into the drying section, out of the cleaning machine, and into some receiver.
  6. Quality is usually of more value to an organization than is productivity. Yes, your management will insist on both. But they are likely to settle for some acceptable product rather than inventory much unacceptable product. That’s why cleaning machines are normally chosen and purchased with more emphasis on if and how good work can be produced and less emphasis on how much of it can be produced. Yet, in some cases, the opposite has been clearly true.
  7. Rinsing is usually more difficult to do than is cleaning. This is because the concentrations of soil are low in the rinse system. Thus the chemical or physical driving forces for their control are significantly lowered vs. the cleaning tank. Equipment for rinsing can take several times more floor space than is needed for tanks where cleaning is done. Cycle time is also likely to be stretched if good rinsing is necessary.
  8. Do all cleaning, rinsing, and drying work at as low a temperature as possible. It is true that solubility of soils is increased, soils are more fluid, and the drying cycle is shortened when parts are kept at an elevated temperature. But the price to achieve those benefits may not be worth the benefit. That bill includes: heightened concern about part damage, increased utility (heating and cooling) costs, additional safety equipment and procedures, reduced life of surfactants, increased solvent loss and associated environmental concern, and a new control set point (temperature). Further, cycle time is stretched to allow energy transfer in both directions.
  9. If cleaning is removal of soil from parts, and rinsing is separation of dirty cleaning agent from more pure cleaning agent, then drying is separation of parts from pure cleaning agent. If rinsing may impose more burden than cleaning (see principle #7), drying is likely to impose more burden than is rinsing. That burden is at least floor space, investment for equipment, cycle time, attention, and energy cost. As with principle #4, dry to no lower level of retained cleaning agent than is necessary. Ask why “dry-to-the-touch” isn’t satisfactory? And, consider nonevaporative methods of separating cleaning agent from parts.
  10. The useful lifetime of cleaning equipment is three to five years. Don’t use a longer time to amortize an investment. After that time, the unit may have “rusted out,” been made obsolete by environmental regulations or higher quality standards, not compatible with then-current business plans, or competitive vs. new technology. When the unit is financially amortized, a decision about replacement is more easily understood.

A "Freebie"

A corollary principle is that equipment for metal finishing must perform as well as equipment for manufacturing articles with metal. It doesn’t matter if the customer rejects the article because it has been made with poor size control, a low-quality alloy, or the surface is contaminated with “water spots.” The outcome is identical in each case—loss of business.

Cleaning equipment has the same value as does any equipment necessary to retain the customer’s business.


Purchase of anything that costs thousands or tens of thousands of dollars and which can have direct impact on the health of your business is worth doing to the best of your ability. Cleaning equipment fulfills that criterion.
You can buy the right equipment for your application—that which meets your quality and productivity needs. You can also not do so, and risk failure. The difference is in your approach to the situation.

Your approach should be that stated by writers more literate and technologists more knowledgeable than this one: figure out what are your needs and meet them. Said another way, don’t let the normal issues of supplier competitiveness, price, proof testing, or desire to have or avoid uniqueness sidetrack you from this mission. Purchase of equipment is simple: buy what you need.

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