In service weld repairs at 400 deg C on 304H S/S

[JonD71]

Has anybody had any experience with carrying out weld repairs to cracking on a 304H stainless steel vessel at 400 deg C. The vessel is not under pressure though operations are not keen to turn down the temperature to repair. Cracks are at a large nozzle to 300mm length. If anybody has had a similar experience welding at this temperature in any stainless some hints would be appreciated as to the feasibility, best welding method and what to watch for etc.

Thanks in advance

JonD71

JonD 71
Australia

 

[unclesyd]

I've done considerable welding at your temperature range of 304H, 304, and 316. Most of this welding was done to repair radial flange cracking on very large flanges.

I have also welded on 4' D x 6' L 316 SS drums that were under 1 to 2 inches water pressure while operating. These welds were not full penetration welds, probably 90%.

On the flanges we initially welded both the 304 and 304H with a 310 SS high carbon rod, SMAW, that was normally used to weld HK-40 but later used both 309 SS and 310 SS SMAW with the same results.
The 316 SS flanges were welded with 310Mo SS SMAW. All weld prep was accomplished with ArcAir gouging using a competent operator. We also used Inco A with the same results.

You should have no problem welding the material unless there is some significant metallurgical damage since the cause of the crack is undetermined at this point.

 

[EdStainless]

Weld prep and cleaning are the real concerns. I like Syd's choice of weld fillers. The biggest risk is that there is something, like sulfur, present that will assure that you new welds will crack also. Many low melting point metals and salts will cause the same issues.

= = = = = = = = = = = = = = = = = = = =
Corrosion never sleeps, but it can be managed.

http://www.trenttube.com/Trent/tech_form.htm

 

[metengr]

We have performed limited weld repairs to 304H SS following the responses above with E310 weld rod at slightly lower temperatures. It sounds like you will be repairing the cracks from the OD surface of a nozzle on the vessel at 450 deg C - is this correct? Have you had cracks appear in this vessel before - OD or ID surfaces?

I would only express extreme caution in performing this repair without knowing the cause of the cracks. I would use an ASME B&PV Code Section IX qualified welding procedure and welder for repairs.

If you are welding on base metal that contains service-related cracks which initiated and propagated thru-wall from the nozzle ID surface, you could develop more serious problems during weld repair, because you would be working blind from the OD surface. If the cracks had initiated and propagated from the OD surface or you could access the ID surface of the nozzle at a flange, weld repair should be relatively straight forward.

What are the contents of the vessel in service?

 

[aybee]

jonD71 please tell us
is it an ASME vessel under pressure when in service? how thick is the cracked area, what is in it? how long has it been in service..roughly? is the crack in an old weld or in the plate?...then we can all have another think about this and come back to you...Aybee

 

[JonD71]

Aybee

Vessel is to Australian Standard AS1210 which is very similar to the ASME standard basically the same. Design pressure is approximatley 30kPa and the vessel has been in service for approximately 10 years.

Cracks seven off at last count are up to 300mm through the shell plate though adjacent to compensation stiffeners on a large diameter discharge nozzle.

Regards

JonD71

JonD 71
Australia

 

[aybee]

JonD 71 please tell us plate thickness, contents, ? sound like it might be fatigue from nozzle loadings ? is the 400c constant or cold/hot/cold etc hard to tell whats wrong from what you have told us.If the design pressure is 30kPa on 300 dia nozzle it does not seem to have needed reinforcing per 1210 , maybe its very thin wall?..Aybee