CLEANING OF EQUIPMENT FOR OXYGEN SERVICE - AIGA

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AIGA 012/04
Chemical passivation is a treatment used to provide temporary corrosion protection of carbon and low
alloy steel surfaces, which have been pickled. Phosphoric acid (H3P04) or sodium nitrite solutions are
used for this treatment. After treatment, the equipment shall be completely washed, drained and
dried. Surfaces treated in this way have a uniform grey colour, occasionally with some highlights of a
reddish brown colour due to deposits of salts of the passivation products. Any blackish deposits left
on the surface which are slightly sticky to touch, are an indication that draining after passivation has
been incomplete. Whitish surfaces with a tendency to be floury indicate incomplete drying.
Acid solutions that attack the base metal or react with contained moisture may require the addition of
inhibitors.
There are commercially available products and solutions designed either for de-scaling or for
anti-corrosive protection, or to fulfil both of these functions simultaneously. The exact compositions of
these products are not always provided. They should not, therefore, be used unless compatibility tests
have demonstrated the safety of the
5.2.3 Solvents
Some chlorinated solvents are still acceptable and established alternatives include hydro
chlorofluorocarbons (HCFCs), aliphatic hydrocarbons and some specialised constant boiling blends.
The use of HCFCs should only be regarded as a transition alternative due to the possibility of their
phasing out in the future.
Chlorinated solvents offer an advantage in that they tend to be usable in conventional degreasing
equipment. A selection of solvents for cleaning oxygen service equipment is listed in Table 1.
Pertinent data that is available on these products is also included.
Although the solvents listed are low in their ozone depleting potential, they are volatile organic
compounds and will, in some cases, also have a global warming potential. This should be taken into
account when considering any investment in cleaning equipment.
In addition to the cleaning ability of the solvent, material' compatibility, toxicity and environmental
issues in the application, and waste disposal aspects must ail be considered when choosing the most
suitable solvent for a given cleaning application. On completion of cleaning it is essential that all
traces of solvent remaining are removed. If necessary, this should be confirmed with appropriate
detection equipment (e.g. halogen leak detector or detector tube for chlorinated solvents). When the
favoured method of cleaning is to use a solvent, its choice will represent a compromise combination of
relevant properties. Solvents used shall be of a stabilised grade of proven suitability.
It is important to ensure that the solvent is compatible with the materials used in the construction of
parts being cleaned. Un-stabilised solvents can cause metal corrosion. The presence of moisture
accelerates the corrosive effects of trichlorethylene and it is therefore essential that care is taken to
maintain the quality of the solvents in use.
Solvent degreasing must be carried out in a well-ventilated area and appropriate personal protective
clothing should be used. The occupational exposure limits/threshold limit values shall be considered.
Any changes of cleaning agent must be accompanied by a rigorous assessment of the risks to health
of those involved in the changed process. Any necessary controls must be established and
information provided to those involved with the changed solvent. This is required by legislation in most
countries.
Flammability is an important safety issue with hydrocarbons.
Alcohol, oil spirits, some solvents and dry residues of aqueous detergents are flammable with oxygen.