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Oxygen Cleaning
Cleaning For Oxygen Service Whitepaper
White Paper By Phil Dale (Co-contributor Handbook for Critical Cleaning – Liquid Displacement Drying Techniques).
Cleaning for oxygen service is best defined as the removal of combustible contaminants from the surface of any equipment or system in oxygen service, including all parts thereof. Essentially, any component that may come into contact with an oxygen rich environment.
The combustible contaminants include organic and inorganic substances such as hydrocarbon material for example oils and greases, paper, fibre, coal dust, solvents, weld slag, rust, sand and dirt. If these contaminants are not removed properly, in a worst case scenario, this can cause combustion in an oxygen atmosphere or at the least rejection of the product due to unacceptable product purity.
Oxygen in its own right is not flammable but it supports combustion. Oxygen can react with most materials. The higher the oxygen content and/or pressure in a system the more vigorous the combustion and the lower the ignition temperature required. Materials that do not normally ignite in atmospheric air will burn and may explode in an oxygen rich environment. In addition the oxygen rich environment will give rise to a higher flame temperature and combustion velocity and the devastating consequences thereof.
The recognition of oxygen’s reactivity has led to stringent requirements regarding the cleanliness of equipment in oxygen service. Strict guidelines exist to ensure that care must be taken in the selection of equipment including all materials and components, all of which need to be oxygen compatible. They must also be free from combustible contaminants as described above.
With this in mind special consideration must be given to any cleaning processes employed in the manufacture and maintenance of all oxygen service systems.
Specific consideration must be given to the following:
- cleaning standard to be achieved (how clean is clean?)
- cleaning procedure specified (or not)
- cleaning agent to be used
- surface properties of the parts to be cleaned
- shape and geometry of the material
- types and amounts of contaminants
- the degree of automation required
The size and capacity of the equipment is determined from:
- the size of the material or components to be cleaned
- the required throughput
Your starting point should be the cleaning standard and procedure. For example *G93 indicates that solvent cleaning is preferable. Solvent cleaning and solvent vapour phase cleaning of components consists of the removal of contaminants by immersion in the solvent, possibly with the addition of ultrasonic agitation and the action of continued condensation of solvent vapour on the component surfaces. The procedure requires that the oxygen equipment, system or component is colder than the solvent boiling point. This allows the vapour to condense on the components and perform a final rinse.
The major significant advantage of solvent cleaning is that re-vaporised solvent is always clean and the contaminants remain in the evaporator liquid section which requires only periodic cleaning out, thus causing a reduction in the frequency of system downtime.
It is also important to note **G127–95 (Reapproved 2000). The effectiveness of a particular cleaning agent depends upon the method by which it is used, the nature and type of the contaminants and the characteristics of the article being cleaned, such as size, shape, and material. Final evaluation of the cleaning agent should include testing of actual products and production processes.
All equipment must, together with the cleaning chemistry, fulfil as a minimum the legislation for health, safety and environment.
The choice of equipment has to be based on the efficiency of cleaning versus cost bearing in mind what is the cost of the problem? If there is no cost there is no problem.
The efficiency is controlled by utilising typical samples, written procedures and requested criteria for cleanliness.
If you need to clean to ASTM G93 – 03(2011) Standard Practice for Cleaning Methods and Cleanliness Levels for Material and Equipment Used in Oxygen-Enriched Environments then all of the above needs to be given due consideration.
*G93 – Standard Practice for Cleaning Methods and Cleanliness Levels for Material and Equipment Used in Oxygen-Enriched Environments
**Designation: G127 –95(Reapproved 2000) Standard Guide for the Selection of Cleaning Agents for Oxygen Systems.
Handbook for Critical Cleaning, Second Edition – 2 Volume Set Hardcover – April 4, 2011by Barbara Kanegsberg (Editor), Edward Kanegsberg (Editor)
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 products are supplied and supported by EnviroTech Europe Ltd. Manufactured in the United Kingdom and available on short delivery times through our dedicated team of distributors worldwide.
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New study disputes TLV for nPB
A detailed comprehensive review of 1-bromopropane studies confirm current recommendations by EnviroTech for occupational exposure levels for safe usage of EnSolv® as a vapour degreasing solvent.
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Update on a safe occupational exposure level for 1-Bromopropane
Prepared for EnviroTech Europe, Ltd.
Prepared by Dr. Mark Stelljes
SLR International Corporation
September 2014
Executive Summary
This paper re-evaluates EnviroTech Europe’s (ETE’s) current occupational exposure level recommendation of 100 ppm for 1-bromopropane (1-BP) [106-94-5] in the vapor degreasing industry in light of the recent lowering of the ACGIH Toxicity Threshold Value (TLV) from 10 ppm to 0.1 ppm. The 0.1 ppm value is based on a study of 86 workers exposed to 1-BP during its manufacturing in China in four different facilities. The authors reported significant effects at all 1-BP exposure levels down to 1.28 ppm. The 1-BP in these facilities had concentrations of the isomer 2-bromopropane [75-26-3] (2-BP) present as a contaminant at about 10-20 times the level sold for vapor degreasing.
There are several factors that undermine the conclusions reached in the paper that a concentration of 1.28 ppm resulted in toxicity in exposed workers. These factors were related to:
(1) Exposure measurements – passive rather than active samplers were used, and concentrations varied by more than tenfold for the same activity.
(2) Exposure via other routes in addition to inhalation – described worker activities indicate substantial dermal exposure, which increases the overall dose of the chemical relative to just inhalation exposure.
(3) Exposure to other chemicals – at least 20% of the workers were previously exposed to 2-bromopropane
(2-BP), and no testing was done for other chemical exposure.
(4) Statistical methods and interpretations – instead of using paired patient-exposure data, authors categorized exposure into groups (e.g., high, low); this resulted in apparent statistical relationships that may not be biologically relevant.
(5) Lack of robust dose-response relationships – when evaluating typical doseresponse relationships, only a single parameter (vibration sense in the toes, a subjective parameter) was shown to be significantly different across all dose levels.
(6) The outcome of the subjective vibration sense test was in part dependent on the testing doctor – this dependency should remove the test and its results from consideration in the paper as a scientifically defensible endpoint.
When all of this information is considered as a whole, it is unlikely that the 1.28 ppm lowest effect concentration reported in the paper is accurate. The interpretations in the Li et al. study are inconsistent with expectations based on the ways in which 1-BP acts in rodents relative to humans. Studies on how 1-BP acts in the body of rats and mice and studies on metabolism of the chemical in humans indicate that humans should be no
more sensitive to 1-BP than either of these rodents.
Based on the weight of evidence available for the toxicity of 1-BP in humans and rodents, there is no credible scientific reason to target an occupational concentration as low as 10 ppm or 0.1 ppm. ETE’s current recommendation of 100 ppm should be maintained, and employers together with vapor degreasing personnel should not be concerned about the much lower levels recommended by the ACGIH.
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 products are supplied and supported by EnviroTech Europe Ltd. Manufactured in the United Kingdom and available on short delivery times through our dedicated team of distributors worldwide.
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ACGIH Threshold For N-Propyl Bromide Solvents
What You Should Know About The ACGIH’s Threshold For nPB Solvents
If you work with industrial chemicals, materials or solvents then you may have heard of the American Conference of Governmental Industrial Hygienists (ACGIH). The ACGIH is a scientific, but non-governmental body of industrial hygienists that publishes Threshold Limit Value (TLV) opinions on chemicals such as n-propyl bromide the base solvent for EnSolv formulations. These TLV opinions are not held to the same standards as limits set by an organization such as OSHA in the USA, but are still published in books available on the ACGIH website. You or someone else in your company might be familiar with these TLVs.
In March 2014, the ACGIH published a new TLV for n-propyl bromide (1-bromopropane). This TLV was set at 0.1ppm, and refers to “commercial grade bromopropane (99% 1-BP with 0.1%-0.2% 2-bromopropane).” 2-bromopropane is also known as isopropyl bromide (iPB). Modern nPB manufacturing processes result in nPB with <0.01% iPB contamination, which is of a pharmaceutical quality.
The 1-BP (nPB) properties referenced by the ACGIH rely to some degree on information first published in 1999 and 2000, which contains information that is out of date and inaccurate when referring to today’s purity of 1-BP. Some of the things to keep in mind regarding ACGIH TLV opinions include:
- TLVs are not determined by speaking openly with scientific experts, but in closed-
- Door meetings.
- There is no scientific consensus backing up ACGIH’s findings.
- ACGIH TLV opinions may involve conflicts of interest and uncertain science.
- The ACGIH is a not-for-profit organization that funds its activities by selling books; it is not a government-sanctioned panel of experts.
The IBSA et al. v. ACGIH lawsuit documents a number of these concerns involving the ACGIH and how they determine their TLV opinions. There is nothing worse than misinformation in our field – not only are safer chemicals such as nPB made to seem dangerous, but chemicals that are unsafe or unsuitable might be seen as acceptable alternatives.
It is of great concern to that in spite of the very demanding regulations already in effect in Europe some manufacturers of very expensive “new” fluorocarbon alternatives to the less expensive conventional solvents choose to imply that recent ACGIH recommendation for a reduction of exposure limits will have legal effect in Europe. This wrong and no credence should be given by users to any “recommendations” except those issued by government regulators.
The EU will establish DNEL (Derived No Effect Level) recommendations under the REACH legislation in due course and until these are issued all properly designed and maintained equipment is perfectly safe for use for vapour degreasing and any suggestion to the contrary may cause unnecessary confusion and restrict the use of this very useful technology.
EnviroTech Europe urges you and others in your company not to rely solely on TLVs, but rather on official and informed sources instead (See US EPA SNAP Approval for 1-BP). For more information on the properties of nPB and related solvents, please visit www.vapour-degreasing.com.
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 products are supplied and supported by EnviroTech Europe Ltd. Manufactured in the United Kingdom and available on short delivery times through our dedicated team of distributors worldwide.
Share this page:
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