Is Your Metal Jacketing Spec Up to Par?

Did you know there are two “new” ASTM standard specifications for metal jacketing?  If you haven’t heard this, don’t feel bad – you aren’t alone.  Our very own regional technical managers at JM IIG have commented that they have rarely met an owner, engineer, distributor, or contractor that has heard about these two new specifications, even though these standards have been in the industry for close to 5 years.  Despite their lack of notoriety, these standards are now available from ASTM, and they are worth reading and considering for your specifications to ensure that the jacketing is robust enough to withstand the rigorous demands of your application.

• ASTM C1729- Standard Specification for Aluminum Jacketing for Insulation
• ASTM C1767- Standard Specification for Stainless Steel Jacketing for Insulation

The purpose of ASTM C1729 and C1767 is to standardize the terminology and nomenclature for the cladding that keeps insulation protected from the weather and the demanding conditions found in an industrial environment.  Below are the we’ve outlined the highlights of the standard:

Aluminum

Type I, II, III, IV, V

• The outside surface treatment of the jacketing
• Bare, painted, etc.…  
• Type I is bare (most common)

Grade 1, 2, 3, 4, 5, 6

• Alloy and temper
• Grade 1 is most common

Class A, C, D, E

• Moisture retarder
• Class A polyfilm is most common

Stainless Steel

Type I, II, IV, V

• The outside surface treatment of the jacketing
• Bare, painted, etc.…  
• Type I is bare (most common)

Grade 1, 2

• Alloy and temper
• Grade 1 (T304) is most common

Class A, C, E

• Moisture retarder
• Class A polyfilm is most common

At this point, you may be wondering why these standards even matters?  After all, isn’t all jacketing relatively the same?  Not quite, and one of the primary differentiators comes down to the required thickness of the jacketing based on the application.

The two ASTM standards provide thickness (gauge) recommendations based upon both the pipe diameter and the type of insulation beneath the jacketing. To paraphrase the standards, larger pipes need thicker jacketing to ensure adequate strength and protection for the insulation. Interestingly, many industry experts, who have been in the industrial industry for decades, are unaware of this requirement.   

Beyond the thickness requirements pertaining to the pipe size, the aluminum standard (ASTM C1729) now also includes provisions for cladding based upon the compressive strength of the insulation it is covering.  The standard identifies “rigid” or “non-rigid” insulations based upon 15 psi compressive strength as the midpoint between the two classifications.  Below is an example of how this new standard would manifest in pipe diameters ranging from 24 to 36 inches:

• Rigid insulation requires 0.020” gauge aluminum
• Non-rigid insulation requires a thicker 0.032” gauge aluminum

These recommendations support a concept that isn’t new to the industry: stronger, high-strength insulations, such as calcium silicate, expanded perlite, and cellular glass, support the cladding, helping to maintain the integrity of the weatherproofing layer. While insulations with lower compressive strength, like fiber glass or mineral wool, may be a less expensive alternative to high compressive strength insulations, their lower cost has to be weighed against the expense of the higher gauge jacketing required for non-rigid insulations.

Bottom line, these new ASTM standards reinforce the fact that although low compressive strength materials may cost less, some of the savings will go straight into purchasing the thicker, more expensive jacketing required by these new standards.   ASTM C1729 and C1767 are part of a greater attempt to improve insulation systems in an effort to keep the insulation dry – which is the first line of defense in the battle against corrosion under insulation (CUI).

If you would like more information pertaining to these new standards, the interrelationship between jacketing and insulation, and how to specify systems that have a robust defense against CUI, we encourage you to attend our upcoming webinar on Wednesday, August 23^rd, “Combat CUI: How to Combine Insulation & Jacketing to Inhibit Corrosion.”  David Shong, Regional Technical Manager from JM, will be co-presenting with Kelly Weiss, Insulation Product and Operations Manager from ITW Insulation Systems, in a webinar detailing critical nuances of metal jacketing and insulation performance pertaining to CUI prevention.

Click here to register to attend.