Nominal Thickness for Clad Material Plate - Eng-Tips

It will depend just what you are trying to decide based on the "nominal thickness".

My experience is that the cladding is only for corrosion allowance, and thus UCL-23(b) applies. This paragraph recognizes that if you order 39 mm composite thickness with 3 mm of cladding the actual clad may exist within the 36 mm base metal thickness, but this is permitted for a "reasonable" amount of cladding without any reduction in the base metal allowable stress even when the cladding material is weaker.

For selecting the PWHT, UCL-34(a) only requires the ordered base metal thickness to be considered. For deciding if the base metal requires impact testing UCL-27 only requires considering the ordered base metal thickness.

The mills will supply and price the material very differently depending on how you specify your thicknesses. For instance, SA-263 para 11.4 permits much larger overruns on clad plate than SA-20 para 14.2. This may not matter on a single small vessel, but can have significant impact on multiple shop built vessels or a large, field erected vessel (extra welding, shipping and lift weight, etc). You can specify nominal thickness (underrun permitted as per the standard Code rules) or minimum thickness (extra $ and weight) for either the base, clad or composite thicknesses. You can specify base thickness plus clad thickness, or composite thickness including clad thickness.

Weld procedure selection for the base metal will only depend on the base metal thickness, but my Code knowledge can't point you at the applicable paragraphs.

Part UCL will be your guide on most items.

Good luck
Geoff Dear All,

Thank you very much for the explanation.

Dear Geoff,

I am trying to decide to use ASME Div.1 or Div.2.

In my company specification,any 'nominal thickness' of the plate more than 38mm,that vessel shall be designed using Div.2 instead of Div.1.

Since the supply plate thickness is 36mm for CS part,it will not require to design to Div.2.

However,after adding 3mm of clad material,the overall thickness plate became 39mm which is more than 38mm.

Therefore,currently i am evaluating several proposal from fabricator and some of them proposed Div .1 and there is several proposed Div.2.

I need to confirm if clad thickness shall be considered in nominal thickness since if corrosion allowance thickness need to be included in nominal
thickness.

Thanks

Many of you may not know this but in my early metal fabricating career I was a certified welder in the architectural metals industry. We made all sorts of custom products, using mostly non-ferrous metals such as aluminum, brass, bronze, and stainless steel.  One of the many products I used to manufacture were architectural metal cladding panels. This craftsman style welding is referred to as fitting, and perhaps the most important aspect of the role, after weld integrity of course, was ensuring a flat, square, and accurate product after the welding process has cooled. This is a process that requires a skilled welder to ensure the production of a quality fabricated panel.

For more information, please visit KLS.

Why does welding aluminum cladding panels cause oil canning?

When you weld two aluminum components together, you must remember that the metal shrinks as it cools. Therefore, as the weld cools, it sucks the two components together. This can result in:

• The frames going out of square
• Angles being pulled tighter than desired
• Oil canning on any large flat surface of aluminum, which is caused by the various forces exerted on it from the heating and cooling process.

So, this brings us on to the next question…

How to do you fabricate aluminum façade panels without panel deformation and oil canning?

The company is the world’s best cladded plate supplier. We are your one-stop shop for all needs. Our staff are highly-specialized and will help you find the product you need.

The answer is simple – don’t weld them! As I mentioned previously, welding cladding panels was a common thing, not only in my career, but in an entire industry but the industry has now moved on. Since then, the architectural metals industry has realized that welding panels required an unnecessary series of steps that could be easily eliminated and in the process also save and produce a superior product and finish.  No more welding, grinding, and polishing, and best of all, no more oil canning!

Why do some fabricators insist that welding corners is better?

As the old saying goes, old habits die hard. While there is nothing structurally wrong with welding corners on aluminum cladding panels, it is unnecessarily costly and time consuming, and most importantly results in unsightly oil canning, grinding marks, and panel dents. Some fabricators will claim that their trained craftsmen take pride in their work and don’t have these issues. However, I was once one of these craftsmen, and our whole fabrication shop only produced the best in architectural metalwork. But as technological advancements came in and the ability to produce a better-quality product, we moved on to new fabrication processes. On another point, the welding of panels requires a skilled craftsman and these are becoming harder to find as my peers and former colleagues move on to other industries as I did or move on to retirement.

Final thoughts on welding metal cladding panels

Speaking from personal experience as a certified welder fabricating architectural cladding panels, I can say with some authority that these days cladding panels are best fabricated without welding.  If you are still skeptical, below are some images showing the contrast between the two:

For more information, please visit clad plates supplier.