Category Archives: insulation and cladding

stress corrosion cracking

Posted on March 29, 2010 | 2 comments

Question:  “Please see attached pictures of the inside of my tanks.  What is causing the pitting in this area?”

Tank Guru:  I suspect that the reason for this damage may be chloride stress corrosion.  Chlorides are a problem for 300 series grades of stainless steel, such as 304 or 316 (most common in tank containers), and stress corrosion cracking can occur when you have the simultaneous presence of tensile stresses along with specific environmental factors such as having a steam-heated/insulated tank.  Most insulation contains chlorides, especially polyurethane, and so it is usually advisable to not have this type of insulation in direct contact with the barrel when the tanks are going to be steam-heated.  Chloride stress corrosion is an increased risk with temperatures above 125° F.  The tensile stresses could be the result of certain operations to the tank, or due to residual stress from the fabrication process such as bending and/or welding.  I think this is why you are seeing the corrosion problem between the head seam and knuckle radius.

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Posted in corrosion, CPV, insulation

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decals

Posted on November 30, 2009 | 1 comment

Question:  “Can I install new decals on top of old decals?”

Tank Guru:  When it comes to the regulatory markings on a container, what is typically specified in various regulations is the size of the required markings and their location; NOT the manner in which they are installed.  There is no rule stating that one cannot install a new decal on top of an old decal.   That said, there is no reason that it wouldn’t be better to first remove the old decal. 

But, if for example the old decal is faded or illegible due to years of sun exposure and likewise adhered to the cladding because of being baked on by the sun and therefore difficult to remove; then I suppose you could install the new decal on top of the old one.  Just make sure that the new decal is securely affixed and easy to read (old decal does not show through).  Thanks for the question.

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Posted in cladding

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cladding for insulation required under Special Provision TP38

Posted on April 15, 2009 | 3 comments

Question:  “Do we need to use stainless steel cladding when insulating tanks with 4″ insulation (as required for PIH products)?”

Tank Guru:  The insulation requirement for toxic products which are considered an inhalation hazard (special provision TP38) is as follows:  “Each portable tank must be insulated with an insulating material so that the overall thermal conductance at 15.5 °C (60 °F) is no more than 1.5333 kilojoules per hour per square meter per degree Celsius (0.075 Btu per hour per square foot per degree Fahrenheit) temperature differential. Insulating materials may not promote corrosion to steel when wet.”

In the simplest terms, 100mm (4″) of any of the normal insulating materials used on tank containers (mineral wool, fiberglass, polyurethane, etc.) more than meets the requirement.  And while it is most common to see tanks carrying PIH products with SS cladding, this is not required and any jacketing material will work.

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Posted in cladding, insulation, insulation and cladding, jacketing, Russell Harrison

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