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Process equipments & Piping











Purpose for Pre-commissioning cleaning:

In any industries, Process equipments and piping must be chemically cleaned to remover mill scale, dirt, greases used as rust preventives, and other foreign materials that could result in operating and maintenance problems such as plugging and damage to rotating equipment and corrosion due to the reaction of scale with the process environment.

Chemical cleaning will be done after completion of construction.

The Cleaning will enable to remove of

• Welding Slag
• Loose Rust
• Mill Scales
• Grease or Oil if used as rust preventives

Following treatments carried out for Pre-commissioning chemical cleaning:

• Degreasing Treatment
• Acid Treatment i.e. pickling
• Passivation

ACID TREATMENT i.e. PICKLING

Pickling is typically performed to remove adherent oxide films resulting from hot-forming, heat treating, welding and other high temperature operations. Welding or heat treatment often produce complex oxides that can vary in color. All these oxides are generally referred to as "scale" and must be removed. Where applicable, alternative mechanical methods such as blasting, shot peening, tumbling, and wheel abrading may also be performed. Abrasives containing iron should not be used. In many cases, pickling of stainless steels is performed in two steps, one for softening the scale and one for final scale removal. Over-pickling, under-pickling and pitting usually are the direct results of lack of control over process variables including acid concentrations, solution temperature and contact time.

DEGREASING TREATMENT

Envirochem Systems provides a specialty chemical cleaning services for Process Equipments and Piping. Degreasing service is the one part of the Chemical Cleaning.
The most common degreasing applications are internal flushing and cleaning of Process Equipments and Piping. This can be done by tank dipping methods or by re-circulating methods using alkaline cleaners.
A common procedure would be to thoroughly clean the parts by close circulating hot water and detergent. Parts that contain higher concentrations of hydrocarbons and grease will, most likely, require solvent cleaning. Certain jobs are required to be thoroughly dried following cleaning. In these cases, we will typically circulate isopropyl alcohol through the part followed by a thorough nitrogen purge.

PASSIVATION

Passivation is “the removal of exogenous iron or iron compounds from the surface of a stainless steel by means of a chemical dissolution.
Typically, treatment with an acid solution that will remove the surface contamination .

The passivation is the Pre-commissioning process which removes FREE IRON contamination left after on the surface of the stainless steel as a result of welding, machining and fabricating processes.

Such type of iron cause to occur corrosion , and if not removed in time it will become difficult. Contamination of iron will deterioration of the component.

In a general context, the term "passivation" means to make something chemically passive, where passive is the opposite of active. Active surfaces react readily while passive surfaces are resistant to reactions, including corrosion reactions.



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