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Condensation Cleaning

The future for solvent vapour degreasing equipment – Innovation driven by legislation.

Vapour degreasing is the simplest but most effective degreasing and cleaning process for industrial use.  It has, until recently, been subject to little change since it was first invented in the early part of the last century. The name for the process is a misnomer as the cleaning is achieved  by solvent vapour condensing on the cooler target parts the hot liquid solvent dissolving oil and removing dirt.

Vapour degreasing is a mature chemical technology on which legislation is now effecting changes so fundamental that the more accurate name for the process “Condensation Cleaning” should be used to reflect the way in which it works. The open topped tanks so ubiquitous in factories and workshops worldwide are no longer acceptable and the alternatives in equipment design and their  fundamental differences in  technology  which guarantee the continuing use of vapour degreasing in the future need to be considered and understood.

In Europe the United States and in other advanced industrialised economies increasingly stringent legislation to control emissions of VOCs and especially solvents has led to new formulations for paints and other coatings where water replaces most of the solvent. In the early days the quality of the coatings was not as good as solvent based coatings but innovation has driven the development of new polymers with results as good as, if not better than, the solvent based originals.

As with coatings, cleaning systems have had to change. With increased regulation users of solvent have been targeted and alternatives are encouraged by the relevant authorities and law makers often without serious consideration of unintended consequences.

For example water based cleaning is the obvious alternative but this has many disadvantages compared to condensation cleaning as although the machines are simple and relatively cheap the processes require multiple tanks for immersion or spray processing or long programmed cycles in batch machines for cleaning, rinsing and drying. Water based processes are slow, energy intensive and occupy more floor space than  condensation cleaning equivalent where only one tank with small footprint is needed delivering shorter process times and most importantly using minimal energy.

The ideal cleaning process would be “Condensation Cleaning” with water but due to the physical characteristics of the water vapour/steam and the inability to carry onto the surface of the targeted parts surfactants to remove the oil, grease and soils and the difficulty of rinsing and especially drying this can only ever be a dream.

A little history of the chemistry helps to explain the changes since the introduction of the vapour degreasing process. Suitable chemicals must be very good solvents for oil, grease, and other industrial soils non-flammable, safe for users and the environment and very stable when heated continuously for long periods.

Halogenated hydrocarbons are the solvents of choice for “Condensation Cleaning”. The process is essentially simple. A tank with a sump to contain the solvent, heaters at the base and condensation coils around the top section to control the height of the vapour is all that is required.  When heated in the sump halogenated solvents produce, a saturated vapour between 3 and 4 times heavier than air at a temperature greater than the ambient conditions. This allows the solvent vapour to condense on the surface of the parts to be cleaned. The condensate dissolves the contaminants such as oil, greases and soils returning the used solvent into the sump of the machine for recycling into vapour which continuously condenses onto the parts until they have achieved the same temperature as the solvent vapour when, with no further condensation, the process is complete. Parts removed from the cleaning machines are very clean, warm and dry.

The most common halogenated solvents, in use for commercial purposes, are non-flammable so present no risk in this process. Perchloroethylene, used mainly for dry cleaning, methylene chloride used more widely in paint strippers and trichloroethylene used for vapour degreasing were the original materials used based on chlorine chemistry. However continuing concern about the environmental impact and danger to operators by exposure to chlorine based solvents, especially trichloroethylene, has led to a continuing search for safer alternatives.

1,1,1 trichloroethane (Genklene from ICI and Chlorothene from Dow Chemicals)  both of which were based on another chlorinated solvent  were to become ubiquitous in the mid part of the last century as a much safer, non- carcinogenic replacement for trichloroethylene. This was an excellent solvent safe for users but which, with increased awareness of the environmental impact of solvents, proved to be depleting the protective ozone layer around the Earth and was subsequently, banned. With the development of the REACH legislation in Europe, which now classifies trichloroethylene as a human carcinogen, usage is allowed but with restrictions and stringent controls for use  authorised in machines which control factory emissions to very low figures close to zero.

Meanwhile cleaning solvents based on 1-bromopropane such as EnSolv were developed in the United States as a drop in replacement for trtichloroethane. EnSolv has an identical profile, stable, non-flammable, with the same physical characteristics such as boiling point and specific gravity and it is an excellent cleaning solvent but without the potential for ozone depletion.

During this time new halogenated solvent blends using trans1.2 dichloroethylene, a highly flammable solvent with similar chemistry to trichloroethylene were also developed for condensation cleaning.  The trans 1.2 dichloroethylene is blended with a variety of different fluorocarbon solvents which are not suitable as cleaning solvents, as they have very low solvency, but are used in these blends as a fire retardants.  An extremely expensive answer to a simple problem, already solved by the development of machines able to safely use the more economical solvents.

As with all legislation for the use of chemicals regulation and restrictions drive development of associated processes and equipment. The most important developments in machines to use solvents for condensation cleaning use two different approaches and  raise difficult questions as to which is the best most economical and simplest in use.

Solvac Automatic hermetically sealed vapour/liquid cleaning system

Figure 1 – Solvac Automatic hermetically sealed vapour/liquid cleaning system conveyor fed.

The single tank hermetically sealed machines favoured by some equipment manufacturers uses a process tank to contain the solvent and a separate storage tank/vapour generator. Baskets, containing soiled parts, are loaded from the top or through access points on the side of the tank. Lids or doors close over the opening and the process tank is hermetically sealed.  Baskets are immersed in solvent, where agitation, ultrasonics or pumped liquid is circulated through the parts.

When the immersion process is completde solvent is removed to the storage tank and vapour fed to the process tank from a vapour generator for rinsing and drying. On completion of the cycle coil,s located within the process tank  collapse the vapour.  The process tank is evacuated by vacuum and recycled through carbon absorption units to remove traces of solvent from the air until the concentration is below limits set by regulators when the lid opens automatically for the basket of parts, clean and dry, to be safely removed and replaced with a further basket.

Variations of process within the hermetically sealed tank are possible using sprays of cold or hot condensed solvent, immersion with or without ultrasonics and revolving baskets to deal with the problems experienced when processing machined and fabricated parts. Continuous external distillation of the contents of the vapour generator is also an option depending on contamination.

The alternative technology is much simpler and cheaper using well tried techniques not requiring the long recovery times of the hermetically sealed processes. The multilevel system uses a standard vapour degreasing tank design with a sealed loading section above the process tank.

Solvac 1000

Figure 2 Solvac 1000 – Hermetically sealed multilevel vapour degreasing system for manual load batch processing.

Components, to be cleaned, in baskets or on jigs, are fed to the automated hoist in the load section manually, by hoist or conveyor. The loading door is  sealed pneumatically to completely isolate the process. The process tank sealing lid opens and the basket lowered into the process chamber. Depending on the soils  simple condensation cleaning can be used or with the lower section being filled with clean solvent for immersion cleaning with or without ultrasonics or power sprays. Revolving baskets are a further option to improve cleaning in blind or through holes or oil ways in castings and fabrications.

With the process completed the basket rises to the freeboard area where the condensation coils are located and parts allowed to drain and dry.  The tank seal opens to allow the basket into the load section while the lid closes to seal the  process tank. A fan is then activated which produces a negative vacuum in the load area. The loading door partially opens to allow a flow of air through the loading section which is exhausted to atmosphere or can be recycled through carbon absorption systems.

As baskets entering the loading space contain parts drained and dried only very small amounts of solvent are carried in the exhausted air which is monitored to ensure compliance with appropriate legislation. When this is completed the door opens fully for removal of cleaned components. The loading section can be fitted with top or side sealed doors allowing baskets to flow through on conveyor systems or be loaded from hoists. No solvent enters the work area.

Both processes will produce parts cleaned to the highest standards but the choice of which offers the best solution needs a little more consideration.

The hermetically sealed vacuum process is complicated with the need to move liquids in the machine. It is relatively slow as the carbon adsorption process needs to remove high levels of solvent from the recirculated airstream from the process tank. This is inefficient as adsorption rates for carbon fall rapidly with increasing saturation.  Final levels of solvent in the tank when the lid or loading door opens will be emmited into the workspace and the area in which the operator is working. Long process cycles reduce throughput.

The simpler multilevel systems where movement of liquids is not required are more efficient and offer much faster process times.  Cost of manufacture is also lower as no liquid movement or vacuum is involved. The extracted loading section ensures no leakage of solvent into the work area which gives complete safety for operators and factory staff.  The disadvantage of the multilevel machine is the height of the equipment compared to the hermetically sealed machine.  This will often need the equipment be installed in a pit for easy access.

Both designs of process machines fully comply with the emission regulations of the EU and U.S authorities. Which to choose will depend on many factors which should be discussed with both the equipment and solvent suppliers who have the experience to advise on which offers the best process for the application. Equipment and solvent work together as a process and it is essential to ensure that the suppliers work closely together to offer a package with high levels of responsible care and product stewardship to ensure the best results and safest installation.

The “Condensation cleaning” process still gives the highest levels of economical cleaning with minimum energy usage, low footprint on the factory floor, safety for the operator, and high production rates with low solvent usage or environmental impact. With the new generation of sealed cleaning machines its future as the process of choice for industrial cleaning is assured.

EnSolv cleaning solvents are supplied throughout Europe.

We can provide you with a Material Safety Data Sheets, independent laboratory reports, product samples and technical assistance..

For more information or advice please telephone us on +44 (0) 20 8281 6370 or use our contact form.

All of our products are manufactured, supplied and supported by EnviroTech Europe Ltd and are available on short delivery times through our dedicated team of distributors worldwide.

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Reduce Corrosion Fretting

Why use of SuperCORR A for maintenance of electrical connections on Gas Turbines improves performance by reducing corrosion fretting.

LP Gas Turbines are used throughout the world by extraction industries and manufacturing plants in remote and hostile locations for essential power production. Dusty and wet environments in deserts, mines, grinding mills, pulp and paper mills and on land or sea drilling rigs for gas and oil production. Turbines powering aircraft services while stationary connect and disconnect many times a day in extreme conditions. These applications and locations test connector sealing continuously allowing dust or water to penetrate. This with the flexing of the connecting cables allows sufficient movement between the metal surfaces of the connecting pins to produce fretting corrosion which reduces, interrupts or produces failures in supply.

Regular maintenance of electrical connectors is essential to be certain of uninterrupted supply.

SuperCORR A is an aerosol lubricant containing corrosion preventive compounds, and, as is the case with all lubricants, they can be worn off over time. A manufacturer of connectors tested SuperCORR A to see what the “life” of the lubricant was in a “rub test”. The typical test is 20,000 cycles, i.e. unplug, plug in is one cycle. The test results demonstrated that after 20,000 cycles there were no failures. It was decided to take it one more step and run the same tests for 200,000 cycles. The results again showed no indications of galling or scoring on the connectors at all. The connector looked and tested as good as new. This test
was run under clean conditions in a laboratory but demonstrates the effectiveness of the protective lubricant in SuperCORR A.

As it meets Mil-DLT-87177B specifications it is used by the U.S. Air Force to protect the intricate workings of the F-16 and F-15 fighter jets and by the U.S. Navy on the P 3 Orion electronic surveillance aircraft. Savings for the U.S. government is estimated at $50 million per year. Commercial Aviation aircraft manufacturers recommend it for avionics and electrical switches and connectors and close mechanical application, especially where flights are in salt fog or high humidity.

Containing extremely long-lasting, proprietary anti-corrosive inhibitors SuperCORR A provides a superior lubrication coefficient and protects components against moisture, wear, general and fretting corrosion, surface static electricity, corona, and other electro migration problems. The super thin non-flammable lubricant film is only 7 microns (0.0007 inch) thick and is formulated without sulphates, chlorides or halogens to meet the RoHS directive. It is unexcelled in preventing deterioration and contamination on all surfaces of electronic equipment.

Very fast drying environmentally acceptable solvents are used as carriers and propellants which will not affect most plastics, substrates, metals or other materials used in connector manufacture. The aerosols are supplied with probes which allow access to pins and connector tubes where the low surface tension repels water, dirt dust and metal particles from blind holes and surfaces to produce thoroughly clean holes and surfaces before a second application applies the lubricant film. Reconnection to the supply with cleaned sections of the connector ensures reliable operation even in the most testing of environments. This easy maintenance from one can of SuperCORR A allows this essential task to be carried out in any conditions quickly, easily and securely.

We can provide you with a Material Safety Data Sheets, independent laboratory reports, product samples and technical assistance..

For more information or advice please telephone us on +44 (0) 20 8281 6370 or use our contact form.

All of our products are manufactured, supplied and supported by EnviroTech Europe Ltd and are available on short delivery times through our dedicated team of distributors worldwide.

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Managing “false alarms” and “no fault found” events in Military avionic systems.

Paper presented at the recent 2017 Aviation Electronics Europe Expo in Munich by Dr. Mustafa Ilarslan, PhD.

In a paper presented at the recent 2017 Aviation Electronics Europe Expo in Munich, Germany, Dr. Mustafa Ilarslan, PhD, discussed –  “The management of “False Alarms” and “No Fault Found” events in Military avionic systems”.

In his paper Dr. Ilarslan explains that “False alarms (FAs) impose a devastating impact on military systems.  An entire aircraft can be grounded because of a single avionics for which there are insufficient spares available. If a FA causes a particular Line Replaceable Unit (LRU) to be called out incorrectly, there is a better than even probability that a second copy of the same LRU will also experience FA and much sooner than expected, the fleet will be deprived of all spares for that LRU.  To then find that the LRUs replaced had No Fault Found (NFF) at the repair depot adds “salt to the wound.” while adding huge sums  for lost time in servicing, aircraft downtime  and unnecessarily high stocks of replacement parts.

SuperCORR A was designed specifically to prevent  these problems in avionic as well as electrical and electronic components and systems failures caused by corrosion, including no fault found failures and problems caused by Cadmium corrosion. SuperCORR A is a proprietary Ultra-Thin Film, Water Displacing Lubricant and Corrosion Preventative Compound, manufactured under license in the UK by EnviroTech Europe Ltd.

SuperCORR A is being used on both military and civilian aircraft to prevent fretting corrosion on electronic and electrical connectors, including F-16, P-3 Orion, Boeing 737’s, C-130, F-15,  DHC-6 Twin Otter, Bell helicopters, Bombardier BD-700 series and Bombardier Challenger 300/350, Learjet 45, Legacy 650, and Hawker to name but a few.

SuperCORR A is also being used at BAE Systems, Honeywell and Raytheon Systems to prevent corrosion from causing avionic, electronics, and electrical systems and components failures and for lubrication and protection of moving parts with a thin dry film.

SuperCORR A meets the requirements of  MIL-L-87177A and Mil-DTL-87177B.

More detailed information can be found in the paper “Electrical connector corrosion prevention Improves reliability and reduces costs” by David Horne which is available here:

David_Horne_06T083.pdf

NOTE that while quoting Dr. Ilarslam’s paper, with his permission, he is not endorsing or recommending the use of any specific product, including  SuperCORR A.

We can provide you with a Material Safety Data Sheets, independent laboratory reports, product samples and technical assistance..

For more information or advice please telephone us on +44 (0) 20 8281 6370 or use our contact form.

All of our products are manufactured, supplied and supported by EnviroTech Europe Ltd and are available on short delivery times through our dedicated team of distributors worldwide.

Share this page:

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https://www.envirotech-europe.com/preventing-hydrogen-sulphide-corrosion/
https://www.envirotech-europe.com/mh370/

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