Pressure Vessel Peening

You really should look it up for yourself. Peening.

http://en.wikipedia.org/wiki/Peening Might be more what you are looking for.

ASME B31.3 Parr 328.5.1 (d)

(d) Peening is prohibited on the root pass and final

pass of a weld.

Peening in engineering usually relates to introduction of surface modification that increases the surface area as well as its capability to withstand higher or more stress reversals.

I guess you want to peen the surface of a pressure vessel to improve its life? That might help although one that I was involved in did not have that performed - we chose the correct material that would allow stressing nd destressing over a number of cycles.

Contact material supplier for further help in choosing and processing.

We are working with an incomplete question here, let me give you an example of peening and welding. the connection between the turbine exhaust and the condenser is known as the condenser neck weld. This can be an extremely long weld an distortion is a real problem.

The procedure used by some OEM' is to make (install) mechanical position references (trams) across the joint in the relaxed condition, After the root pass you can peen the weld to relieve the stresses and bring the trams back to what was a stress free condition. Tooling becomes a matter of ingenuity memory tells me we would use chipping guns with rounded off tools or things of that nature.

If this is the gist of your question then you might be interested in this site

http://www.welding-advisers.com/Welding-distortion.html

Sometimes stress corrosion depends on if the material is in tension or compression. Peening can change the stress. For example the outriggers in the luner module of the moon craft (lunear module) were shot peened to resolve a stress corrosion problem. NASA TECHNICAL NOTE: NASA TN D-7084; APOLLO EXPERIENCE REPORT - LUNAR MODULE STRUCTURAL SUBSYSTEM; by Studey P. Weiss; Houston, Texas 7 7058; MARCH 1973. Descent-Stage Shear-Panel Fatigue and Thickness Control Stress Corrosion

Dean Trytten: Anchor Elite, LLC www.anchorelite.com This is something I read about in the old days when attending NC State University.

Peening is related to welding only. It is mostly done for each pass (when the weld metal is at high temperature) during the welding of cast iron and rarely during carbon steel welding.

Peening means mechanical working of the metal using impact blows with a hammer or any other mechanical means.

Advantage is that, the shrinkage of the weld deposit can be counteracted by peening, which tends to stretch the metal.

Upsetting or expansion of the metal by peening is most effective at higher temperatures where yield strength of the metal is rather low yet, on the other hand, most of the distortion problem occur at lower temperatures after the yield strength has been restored to it s higher value.

The disadvantage of peening is that, it work hardens the surface of the weld metal.

sridhar.

For pressure vessels as per ASME Sec. VIII Div. 1, peening is allowed to do on the weld in order to control distortion, release of residual stress or to improve quality of the weld. But peening should not be done on root pass and final pass unless the weld is subsequently post weld heat treated. In no case, peening shall be performed in lieu of post weld heat treatment required by code rules. See ASME Sec. VIII Div. 1 UW-39. Hope this would help. Regards, Ashfaq Anwer http://forums.thepetrostreet.com