Merits of an Aqueous Parts Cleaning System

Aqueous Based Systems

The alternative to Solvents is aqueous based systems, which use water or emulsions as a cleaning media. Emulsions are relatively simpler to handle, wash and recycle. But there are issues that are faced during the disposal of the emulsion waste when the media is to be cleaned.

All emulsions are categorised as water in oil or oil in water types. 

The emulsions are made of emulsifiers which have hydrophobic and hydrophilic ends.  When they are brought in contact with water, the hydrophobic end attaches itself to water molecule and the hydrophilic end is free and can easily attach itself to any oil, grease or similar contaminant. This helps in removal of the contaminant from the media or the substrate.

Emulsions are made by mixing water and the emulsifier under immense shear and pressure to create a colloidal solution that has a dispersion of emulsifiers in water. Emulsifiers have the same property as any hydrocarbon making it an ideal compound to be used in the cleaning. The emulsions are  also made of stabilisers, buffers and other chelating agents.

There are many advantages of using Emulsions. Temperature of washing can be increased and it can also be operated in an open system. It’s also compatible with most metals, non-metals, plastics and alloys. Most emulsions are stable over a wide range of ph, temperatures and can accommodate additives needed in the washing process.

However emulsions need a process of rinsing and subsequent drying. The rinsing is compulsory as we need to remove the detergents and soap remains from the component. This process is not required when dealing with a solvent based system.

A typical aqueous cleaner is 3 stage:  

1) Washing

2) Rinsing

3) Drying.

Most aqueous cleaning agents are made of various compounds to accommodate different processes.  They can incorporate Chelating agents, sequestering agents, anti-rust compounds, anticoagulants, buffers, stabilizers and other such compounds. These Chemistries are detailed in a different book.

 In summation it can be said that most metals clean and dry faster in solvent based systems, but we need to study the economics of using the solvent must be studied in detail. Aqueous technologies are safer, healthier and less expensive too.

Both Methods have disposal issues.  There is a change in the mind-set of existing users who are moving towards thee aqueous based solutions. Class 1 level of washing needs be augmented with a newer generation of chemicals.

A Layman's Guide : Wet Cleaning of Industrial Parts

Chemistry of Wet Cleaning

The washing of Small Industrial Parts and Components is carried after an assessment of the safest process that can be employed. The factors that determine the decision also takes into consideration effect of water , detergent, oil, or solvent on the component.

Types of Media Used for Cleaning

Though water is the safest and most reliable media for cleaning, it effects some metals. Another factor could be that certain contaminants are not removed by water and may require special process or attention. The choices of available media are:

·                     Water: Cold, Warm or Steam.

·                     Solvents: Hydrocarbons or Fluorocarbons.

·                     Air: Gasses like CO2.

·                     Chemicals: Alkaline or Acidic.

·                     Energy: Radiation, Laser or Plasma.

The first question is whether or not to use water? Can it achieve the cleanliness by air blowing?

It's only when the answer to both the questions is a resounding NO, does one proceed further.

Cleaning in air can be achieved for materials that have less degree of dirt or have such surfaces and contaminants that can be easily blown off. In such cases, contaminants also can be blown away or wiped off using steam.

Processes used in Wet Cleaning

For cleaning with water, chemicals and solvents some of the popular processes are:

1.    Rinse : Room Temperature, Hot or Cold 

2.    Power Wash: Using water and detergent under high pressure in closed compartments made of MS or sheet metals cabinets. 

3.    Bubbler or Gas Rinse: Forcing air through the liquid media to pass through the parts. Sometime Co2 is also used. 

4.    Rotational: Movement by Rotation, Pivoting or Oscillation etc. 

5.    Ultrasonic: The technologies include Acoustic and Resonance.

6.    Megasonic: High Frequency Ultrasonic.

7.    Turbulator: The water is made to churn within the Tank like that of a Home Washing Machine. 

8.    Sprinkler: Like a shower 

9.    Spraying: Using a Nozzle jet that can force water , solvent or Oil out with force.

10.  Hydroson: A technology that combines water and Ultrasound.

11.  Dunking: The component is pulled out of the Media and dumped back.

12.  Liquid Co2: High pressure Co2 is used as a blasting media

Equipment used in Parts Cleaning:

The different type of equipment used depends on the complexity of the ideal washing process.
Most popular systems include:

1.    High pressure Water jets

2.    Sand Blast Systems

3.    Glass Blasting Systems.

4.    Ultrasonic Cleaner

5.    Megasonic Cleaners

6.    Oil Tanks.

7.    Compressed Co2 Systems.

8.    Laser Ablation.

9.    Chemical Scouring Agents

We will discuss each of the above mentioned processes in the next few posts.

How Four Power Factors Affect Ultrasonic Cleaning

Effect of Power on Ultrasonic Cleaning.

Hello again..

Well, since I have been talking about the various things we are learning in finishing industry,it might be apt that we also speak the factors that affect the performance in ultrasonic cleaning.

Ultrasonic Power is a critical factor in deciding the effectiveness of a cleaning System.

It’s generally accepted that 50 W per litre is acceptable level to induce cavitation in a cleaning bath of the system. However there are factors that must be considered.

What’s loaded in the tank?

The washing component could be made from  plastic or cast iron . Will the power requirement capacities change? An honest answer is yes, In order to maximise the cavitation efficiency the power will have to be altered. The ability of component to absorb the energy and vibrations are extremely important. 

The relative density of the medium?

The medium in the tank could be could be water or a solvent ( specific gravity < .099 or > 1.44) Will the power rating differ? Yes, it will.

Changes in the media , when bath temperatures of 66-75 degree celsius is achieved?

There are materials whose properties change dramatically with temperatures. Thereby the ultrasonic power would need to be adjusted accordingly. Certain fluids drop in Viscosity at elevated temperatures.

What about using different viscosities of fluids to clean?

The relation between the power and the viscosities of the fluid is directly proportional. The thicker the fluid, the more power would be required, The thinner the fluid, the lesser the need of power.

People always want to know what is the ideal cleaning power of a tank. The answer to this varies from person to person due to different perspectives. They have their own standard or interpretation to such a question.

The cleaning ability depends on a few set factors, such as:

1.    Actual electrical power input

2.    Cleaning solution used

3.    Transducer matching

4.    Physical construction of the tank

As the manufacturers of these systems, we use universal electrical power expressed in RMS Volts or Watts to evaluate cleaners. The tanks are then properly sized according to the industrial standards of power levels for cleaning levels, as is, so many watts/gallon. Like I mentioned above, 50 Watts/litre is typically and widely used and is categorised as a high power cleaner. In a few cases, 35 Watts/litre is used and is categorised under lower power industrial cleaner.