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DPCNews 023 - ISO 12706:2009 Standard: Missed opportunities

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Written by Administrator
Thursday, 01 April 2010 09:53

April 2010

1- Introduction

The ISO 12706:2009 standard has been published and it supersedes the ISO 12706:2000 standard.
Time has come for us to draw your attention to some missed opportunities.

2- First missed opportunity: to rinse is not to wash and to wash is not to rinse

In many documents, the words ‘‘to rinse’’ and ‘‘to wash’’, ‘‘washing’’ and ‘‘rinsing’’ are used as equivalent. Same situation in French regarding ‘‘rincer’’ and ‘‘laver’’, ‘‘rinçage’’ and ‘‘lavage’’.

Don’t you feel any difference between ‘‘I wash my hands’’ and ‘‘I rinse my hands’’?
If we can rinse our hands with water, we need soap to wash them. Soap is made of surface active agents (surfactants), ingredients used in penetrants. However, the surface active agents (surfactants) are classified after their hydrophilic/lipophilic balance (HLB value). Those used in water-washable (WW) penetrants are not the same as those used in post-emulsifiable (PE) penetrants. To remove these last ones, a hydrophilic emulsifier is needed, which comes as a surfactants concentrate, which the Anglo-Saxons initially called "detergent".

When using a PE penetrant with a hydrophilic emulsifier, the excess of penetrant removal is achieved in a different way.

After penetration time has elapsed, water is sprayed onto the parts surface or parts are immersed in a tank of water (agitated or not). As penetrant and water are not miscible and do not emulsify this step is used only to mechanically remove most of the excess of penetrant (generally from 75% to more than 90%). Doing so, we know that a small layer of penetrant remains on the surface which cannot therefore be claimed as clean. So it seems to us better fit to call this step ‘‘rinsing’’ instead of ‘‘washing’’.

When emulsification time has elapsed, water is sprayed onto the parts surface. The emulsified penetrant and hydrophilic emulsifier are totally washed off during this step. So, it is more appropriate to call this step a ‘‘washing’’ rather than a ‘‘rinsing’’.

Doing so we point out the physical phenomena involved, and we think it is easier to understand.

It would be worth writing these terms in the standard; our purpose is that both underneath proposals are soon discussed:
• Term "Water rinse": Definition: ‘‘Removal with water of most of the excess of the post-emulsifiable penetrant from the test surface before application of the hydrophilic emulsifier.’’
Term "Water wash": Definition: ‘‘Removal with water of the excess of the water-washable penetrant or removal of the post-emulsifiable penetrant after emulsification.’’

What do we see in the ISO 12706:2009 standard?
• The terms ‘‘rinse’’ and ‘‘dip rinse’’ have been deleted.
• Our proposals were not taken into account.

3- Second missed opportunity: the wipe-off technique

The ‘‘wipe-off technique’’ is a currently used process specific to the penetrant testing method.

That's why a paper released on our Website in September 2009 dealt with this topic.
The current word in English is: ‘‘wipe-off technique’’.

This technique is not written in the ISO 12706:2000 standard. We made the following proposal for the following version of the standard:

Doubt removal. Definition: With fluorescent penetrants, this is intended to check and to interpret indications beyond criteria. Wipe the indication smoothly using a soft paintbrush or a swab lightly moistened with a volatile solvent such as acetone. Then spray a light coating of a solvent-based (non-aqueous wet) developer for linear indications (or no developer for non linear indications). If, within two minutes, the indication reappears, under ultraviolet radiation, the discontinuity is confirmed.

Our proposal was not taken into account.

4- Terms not mentioned in the standard

Finally, the following terms would have to appear there:

Blue haze, combined radiometer/luxmeter, digital luxmeter, digital radiometer, dust storm cabinet, fluorescent transparent comparator, hand held refractometer, high temperature penetrant, high temperature remover, illuminance, low temperature penetrant, overshoot, overwashing, thixotropic emulsifier, thixotropic penetrant, (UV-A) ultraviolet irradiance, UV-A source, Wood's glass filter.

5- Conclusion

We do hope our comments will meet some of your concerns and will help you.

As far as we are concerned, we hope that the Technical Group in charge of the next revision of the ISO 12706:2009 standard will finally consider our comments.

References

ISO 12706:2000 Non-destructive testing - Terminology – Terms used in penetrant testing, International Organization for Standardization, Geneva, Switzerland, 2000.

ISO 12706:2009 Non-destructive testing -- Penetrant testing -- Vocabulary, International Organization for Standardization, Geneva, Switzerland, 2009.


We, Pierre CHEMIN and Patrick DUBOSC, welcome any comment, any idea. If you have some examples you would like to see discussed here, please give us all the useful indications. If you require confidentially, we would modify locations, names and some parameters to prevent any traceability.
Nevertheless, we are convinced that our site may be a kind of surge-valve: the topic is NOT to target this company, or that auditor; but it is always to make users think, to make them ask themselves, or others, the right questions.
We may also give advice, once again on a confidential basis if needed: please, feel free to ask questions, to document our data basis: about Material Safety Data Sheets (MSDS), about environment, a chemical name you don't understand, a Penetrant process you have heard about, etc.
We have plenty of examples, some being out of all the specifications/standards, which led to the discontinuities detection, when the "current, normal, processes" prevented discontinuity finding.