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CTG Technical Blog

Stainless Steel can RUST?

In general, we view stainless steel as an ideal material for the construction of industrial cleaning equipment.  It laughs off strong caustics and most other cleaning chemistries, provides long life in the case of ultrasonic transducer surfaces and, in general doesn’t rust or oxidize in a deleterious way giving years, even decades, of service in difficult environments.  The fact remains that in order for stainless to perform the way we want and expect it to, it must be used properly.  It does not, for example, tolerate chlorine bleach, especially in a system with ultrasonics and can “rust” although corrode or...Read more

Questioning Particle Generation Due to Cavitation Erosion as a Source of Contamination

Ultrasonic cleaning is widely used for removing particles from surfaces.  It is generally agreed that the high energy of implosions of cavitation bubbles break the bonds holding particles to the surface being cleaned and that liquid motion (streaming) carries the particles away once they have been dislodged.  However, it is also well known that ultrasonic cavitation and implosion will generate particles as material is eroded from surfaces as cavitation bubbles implode in proximity to them by a process of ultrasonic erosion similar to that seen on a ship's propeller.  A glass beaker, aluminum foil or a lead coupon subjected to long...Read more

Conductivity Calculations

Previous blogs have talked about heat conductivity in very general terms to produce a foundation for this somewhat more technical view for those of you who like formulas and numbers. Conductive heat transfer can be expressed with "Fourier's Law"
  • q = k A dT / s
  • where
  • q = heat transfer (W, J/s, Btu/hr)
  • A = heat transfer area (m2, ft2)
  • k = thermal conductivity of material (W/m K or W/m oC, Btu/(hr oF ft2/ft))
  • dT = temperature gradient - difference - in the material (K or
  • ...Read more

Heat Conductivity and Convection

Heat conductivity is a measure of the ability of a material to transfer heat within itself.  For example, if you heat one end of a short piece of copper wire, the heat is quickly distributed throughout the wire by conduction.  This can be easily demonstrated using a short piece (1 to 2 inches) of heavy gage copper wire and a small torch or gas lighter.  Hold the wire at one end and apply the torch to the other.  It won't take long before the copper becomes too hot to hold. Heat moves by conduction through different materials at different rates depending...Read more

Heat - Definitions and Concepts

Temperature has been identified as one of the important variables in cleaning - arguably the most important.  So I thought it might be worth some time to develop a little understanding of heat - - especially how it is generated and transmitted. Heat is a form of energy.  The amount of heat contained in an object determines its temperature.  The more heat an object contains, the higher its temperature will be.   The amount of heat in an object can be increased by adding heat via conduction or radiation from another object at a higher temperature.  In the case of conduction, the two...Read more

Exhausting Gasses Produced by the Cleaning Process

In many industrial cleaning processes it is necessary to exhaust emissions that unavoidably result from the cleaning process.  The reasons for exhaust can take on a large range -

  • Remove heat that would otherwise raise the temperature in the cleaning area
  • Remove humidity that would otherwise raise the humidity in the cleaning area
  • Remove toxic fumes that might otherwise be dangerous to workers
  • Remove mists of oil and other contaminants
  • Remove dust and other particles to prevent air contamination

The process of exhausting usually starts with an exhaust fan with appropriate inlets or vents designed to capture the contaminants to be exhausted.  Capturing the offending contaminants, however, is only a part of the...Read more

How do you measure surface tension?

In the world of industrial cleaning technology we talk about surface tension a lot! So much so, in fact, that it is hard to enter into any discussion of cleaning without having the subject of surface tension arise.  In cleaning chemistry, for example, we are always looking for lower surface tension to promote penetration of small surface features and blind holes.  Surface tension has a major effect on ultrasonic cavitation and implosion.  A less well-known fact is that surface tension has a significant effect on the droplet size and pattern produced by spray nozzles.  So, if this thing called surface tension is as...Read more

Surface Tension and/or Wettability

A few days ago, I sat down to write what I thought would be a simple explanation of surface tension and how it is measured in the laboratory (a blog which will be published shortly if I can figure all of this out).  In doing the normal background research, however, I started to see contradictions that did not align with what I thought I knew about surface tension.  The culprit was wettability.  Soon I was in a circular argument with myself regarding the two and how to differentiate them.  Contact angle, for example, is a measure of wettability...Read more

Reliability of Plumbing Fittings - Threaded vs. Compression

Wherever there are liquids there are leaks - it's inevitable.  Leaks, of course cost money in downtime and repair of industrial cleaning systems.  So, you ask, what is the best defense against leaks. Most leaks occur where one piece of plumbing connects with another.  A pipe to a valve, unions, connections to pumps and filters and connections to tank fittings.  Other than connections that are metallurgically or adhesively bonded by techniques such as welding or brazing in the case of metals or adhesives in the case of polymer materials, liquids are contained simply by two surfaces wedged against each other.  Let's...Read more

Ultrasonic Drying - Not Yet but Possible???

There has been a lot of buzz lately on the internet regarding work at the Oak Ridge National Laboratory to develop a dryer that uses ultrasonics instead of heat to dry things.  The major thrust seems to be to replace the conventional domestic clothes dryer (which uses heat to evaporate water) with one that uses ultrasonics to atomize instead of vaporize water to dry clothes.  Claims include drastically reduced energy consumption and shorter drying times.  As a result, there has also been some buzz about using the same idea (ultrasonics) to dry parts after ultrasonic cleaning.  The logic being that the ultrasonic...Read more

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