CLEANING OF EQUIPMENT FOR OXYGEN SERVICE - AIGA

- frequently
- occasionally
4
AIGA 012/04
4.1.3.1 Methods to Compare the Efficiency of Cleaning Agents
It is necessary to have standard methods in order to compare the ability of cleaning
procedures/agents to remove oil and grease contaminants from metals.
In principle this can be carried out by contaminating test coupons, cleaning them and evaluating the
cleaning effect by an adequate inspection method.
ASTM has also developed two standards which may be used for these purposes:
- ASTM G 121 "Standard practice for preparation of contaminated test coupons for the evaluation
of cleaning agents".
- ASTM G 122 "Standard test method for evaluating the effectiveness of cleaning agents".
4.1.4 Health, Safety and Environmental Aspects
The ideal agent is non-toxic or at least has a low toxicity. The main factors to take into consideration
are:
- Inhalation effects
- Skin effects
- Eye effects
There are four main issues concerning the environment:
- Emission to water
- Waste disposal
- Emission to air
- Energy.
Energy and emission to water are the main questions for consideration for aqueous cleaning, whilst
emission to the atmosphere is of greater relevance for solvent cleaning.
For environmental aspects see also IGC Technical Note 515/95 "Guidelines for Environmental
Management"
4.1.4.1 Emission to Water
Whichever process is used, contamination of water arises from improper waste disposal, inadequate
effluent water treatment or in the case of solvents, accidental spillage caused by improper handling or
storage.
4.1.4.2 Waste Disposal
Degreasing with solvents gives rise to a residue containing oils, fats and greases. The solvent content
can easily be reduced by distillation either in house or by a licensed recycler, thus recovering useful
quantities of solvent. The residue emerges as a highly concentrated final waste.
This should be disposed of by a licensed contractor and procedures should meet local regulations.
Support and guidance are also available from the solvent suppliers.
Cleaning in an aqueous system generates two types of effluent:
- The spent cleaning bath contains chemical products necessary for the cleaning process and is
also contaminated with oils and greases. This residue must be treated in a wastewater treatment
plant which also generates a sludge requiring further processing before disposal.
- The rinsing effluent is less contaminated, although still containing dissolved salts. Some effluent
may be recycled to an earlier cleaning stage. Any final effluent will require treatment before
discharge.
The regulations for the treatment of spent aqueous cleaning effluent vary considerably from one
locality to another.