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Sinner’s Circle & the 4 Factors of Cleaning

There are many things you should consider before ordering a custom parts washer, including its price, speed and ease of use. The most important thing to evaluate is your cleanliness standard. What do you need to clean, and how clean does it need to be? Complex shapes, blind holes, cross holes and fragile materials make cleaning more challenging. 

Once you know what you’re cleaning, you can determine what “clean” means to your company or customers. How clean do the parts need to be? How will you measure cleanliness? Some companies have requirements that involve analyzing contaminants at the microscopic level, while others only need a simple wash and rinse. 

Each machine relies on interdependent factors to achieve your clean. These factors vary based on the level of cleanliness needed. What are the factors that influence the cleaning process of equipment and parts? Keep reading to learn how time, temperature, chemistry and mechanics factor into your ideal clean. 

Sinner’s Circle & Factors of the Cleaning Process

In 1959, Chemist Herbert Sinner identified four factors involved in effective cleaning: time, temperature, chemistry and mechanics. These factors work together to complete a successful wash cycle. 

If one factor is modified, you must change the other factors as well. For example, increasing the concentration of the cleaning solution may call for reducing the temperature, wash time or level of agitation. Often, these cleaning variables are visually represented by four parts within a circle named the Sinner’s Circle. 

A visual representation of Sinner's Circle. A diagram including the factors of cleaning: time, temperature, chemistry and mechanics.
A visual representation of Sinner’s Cirlce.

1. Time

One factor of cleaning is time. How long does it take for an aqueous cleaning solution (or chemistry) to work its magic? Whether the parts are soaked or sprayed, the time they are exposed to the chemistry affects cleanliness. The longer a part is in contact with the chemistry, the more time the chemistry has to attack soils. Thus, the cleaner the parts will be. 

Think about the way you wash dishes at home. Food-covered plates are difficult to wash later if you leave them in the sink. You need extra elbow grease to get them clean. If you let the same dishes soak in soap and water, you can wash them easily. The more time the plates soak, the cleaner they will be! Similarly, leaving parts exposed to a cleaning solution for longer provides a better clean. 

2. Temperature

Temperature affects cleaning efficacy in most scenarios, which is why heated parts washers are standard. As temperatures heat up, the speed at which parts are processed increases. Heat causes molecules in the cleaning chemistry to move and vibrate faster, which quickens the reaction between the soil and chemistry. 

As a rule, efficacy increases as the solution’s temperature rises but only up to a certain point. The top operating temperature refers to the highest temperature at which the cleaning solution is effective. Any temperature above the top operating temperature will no longer speed up the cleaning process and could adversely affect the parts.

Typically, parts washers utilize aqueous spray cleaning. These machines operate best when heated at 140 degrees to 180 degrees Fahrenheit. 

Working with a manufacturer will help you find the right balance of time and temperature. If the water becomes too hot, the solution could evaporate and leave behind unwanted residue. Evaporative losses affect your ability to maintain the continuous flow of water and cleaning solution.

With certain materials, a solution that’s too hot could tarnish parts. For example, brass parts can tarnish once you remove them from extreme heat. Reducing the temperature and extending the washing time can prevent any ill effects high temperatures pose to the parts. 

3. Chemistry 

Parts cleaning solution, or chemistry, is chosen based on the part’s material and the soil. Water is the base of all aqueous cleaning solutions. Detergents, inhibitors and buffers are added to the solution as needed. The exact chemistry and its concentration are tailored to your application. 

  • Acidic solutions (pH 1-5). With a pH of 1 to 5, acidic solutions are not used for general cleaning. Treating surfaces, descaling and removing tarnish or rust are uses for acidic aqueous solutions. 
  • Neutral solutions (pH 6-9). Mild chemistries with a pH between 6 and 9 have less cleaning power and are best for applications with light soils, such as metalworking fluids, or delicate alloys. Neutral solutions are easy to rinse away because they don’t leave behind residues. 
  • Alkaline solutions (pH 9-12). These chemistries are used for general cleaning. Alkaline solutions remove oil, grease and organic soils within a wide range of temperatures. 
  • High alkaline solutions (12+). Tougher soils like heavy grease, carbonized contaminants and paint need an aggressive parts cleaning solution. High alkaline aqueous solutions fit the bill, but they require more rinses to prevent corrosion.

4. Impingement or Agitation

The last factor of Sinner’s Circle is mechanics. Agitation (or impingement) in cleaning is the final variable that affects how clean the parts will be. Many aqueous parts washers apply mechanical movement to knock contaminants off the parts. 

Added force can come from pressurized spray or parts bumping against each other. Agitating parts washers may include rotating baskets, sprayers or ultrasonics to agitate the parts or aqueous solution.

  • Sprayers. Spray impingement refers to the pressure and volume of the spray used. The distance from the spray nozzle to the part affects impingement. Impingement is stronger when the nozzle is closer to the parts. Spray manifolds can be combined with immersion tanks to offer more turbulence underwater.
  • Rotating baskets or turntables. Cabinet-style washers use rotating baskets or turntables to move parts as they are sprayed. Part-on-part contact, in addition to spray contact, helps remove soils. Baskets also keep smaller parts, like ammunition casings, together.  
  • Vertical agitation. Simple parts without blind holes or unique grooves may benefit from vertical agitation, which is simply a mechanical process of moving parts (often in a basket) up and down repeatedly. 
  • Ultrasonics. By emitting sound frequencies underwater, ultrasonics loosen stuck-on soils. Ultrasonics use a process called cavitation that causes surrounding water molecules to explode upon contact with an object. The force of the explosion shakes off debris. Companies with complex parts, including those with grooves and blind holes, commonly use ultrasonics.

Rinsing and drying are also key cleaning components, though they are not included in Sinner’s Circle. Rinsing removes loosened soils and any residues left behind by the chemistry. Some parts need to exit the cleaning stage completely dry. Any remaining water on the surface could contaminate the next phase in manufacturing. 

When you consider these factors, you and your manufacturing partner will be able to identify the right chemistry and requirements for your application.   

Get Your Aqueous Parts Washer 

Are you ready to give aqueous cleaning a try? At Jenfab, we don’t shy away from customization. We build custom parts washers in addition to standard models. We also provide free, in-house test washing to ensure the system and chemistry meet your cleanliness standards before you make a purchase. 

Request a quote from us today or call (800) 524-9274 to tell us about what you need in an aqueous parts washer. 

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