nonpressure part attach to pressure part by welding

[kevinkzh]

according to HG200.7,nonpressure part attach to pressure part by welding, what key points should be considered, I am a fresh, hope can be helped. thank u!
if welded, they shall be of weldable
quality. The allowable stress value shall not exceed
80% of the maximum allowable stress permitted for similar
material in Tables HF-300.1 and HF-300.2. Satisfactory
performance of a specimen in such service shall not make
the material acceptable for use in pressure parts of a vessel? how to understand?

 

[InspectorByDay]

kevinkzh,

Basically, Code is allowing you to use material that is not listed in either Tables HF-200 or HC-200 for non-pressure retaining parts. If you opt for this route, then you must take the following under consideration:

Material used for non-pressure parts must of weldable quality:

How do you prove it's of weldable quality? Pretty much, you have to qualify a Welding Procedure Specification in accordance with Section IX using that material and the carbon content cannot exceed 0.35%.

If the maximum allowable tensile stress for the material is >80% of a Code-allowed material of similar chemical composition, then it is not allowed.

These requirements typically prevent Manufacturers from using non-approved material for non-pressure parts. There are three main reasons:

1. WPSs are expensive to qualify.
2. Similar materials have similar tensile properties.
3. Most QC Manuals stipulate that all material shall be of an SA or SB (ASME) specification.

The only instance where I have seen an advantage to using this clause was a Manufacturer who had identified a non-accepted, non-ferrous material with excellent thermal conductivity. They welded it to SA-178 Gr. A tubing as extended heat transfer fins.

However, if you are looking to save a buck you can order ASTM, API, EN material and re-certify it to meeting the equivalent ASME specification in accordance with HF-206 for wrought construction.

Regards.