Corrosion Under Insulation: The Challenge and Need for Insulation (Part 2 of 4)

The Role of the Insulation System

It’s a common consensus among experienced people dealing with CUI that dry insulation systems simply don't exist in the long run. They therefore tend to be regarded as a bad influence. In addition, people have believed for decades that cladding/jacketing is 100 percent weatherproof and, in combination with elevated service temperatures, that water or moisture could never get trapped. This idea resulted in many cases in which piping, other that the basic shop primer, wasn’t even extra coated.

Cladding/jacketing is primarily designed as weatherproofing and not as a vapor barrier. Depending on service temperature and ambient conditions, condensation within the insulation system may not be avoidable, and therefore needs to be addressed in the engineering phase. In other situations, water enters into the insulation system through failed or broken cladding/jacketing. This can be caused by:

• Foot traffic
• Inadequate design
• Incorrect installation
• An insufficient maintenance strategy

Overlooking all possible CUI causes in relation to a consequence of the failure of piping systems or equipment, there's a justification for challenging the need for insulation.

The oil crisis during the 1970s brought new insights on energy savings and resulted in other design criteria for thermal insulation for the (petro)chemical industry. In some cases, this resulted in excessive insulating, which was not always economically feasible. However, recent geopolitical CO₂ reduction goals persuaded many asset-owners to re-evaluate these old goals and translate them into new company policies.

Below is a flow diagram that provides a few logical steps to understand whether insulation is necessary or could be replaced.

Reasons for Insulating

The first question that always has to be answered is the reason for insulating, which can be one or a combination of the following:

• Heat conservation or energy saving
• Process control
• Freeze protection/winterization
• Personnel protection
• Noise reduction
• Fire protection

These reasons determine the choice of insulation materials and the type of cladding/jacketing used. There are various insulation standards and guidelines around the world, but I would like to recommend the CINI Industrial Insulation Manual.

When going through the above flow diagram, we see that only insulation for personnel protection could maybe be considered for removal and replacement with something like protective guards. However, because environmental and energy-saving goals have become more important in recent years, removal of insulation even for this reason should be critically assessed.

Source: 

Johan Sentjens, January 30, 2015

http://www.corrosionpedia.com/2/1372/corrosion/corrosion-under-insulation-the-challenge-and-need-for-insulation

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