Buildup Cast Iron ASTM A216

[boorishjam]

I work in hydropower and I'm the client of a Kaplan turbine.
The runner is made of cast iron astm a216 wcc. During the machining of the windows of the runner where the blades are supported, the manufacturer made a mistake and removed 10mm more than necessary. The design code is ASME XIII.
The manufacturer welded buildup more than 10mm and then machined again to the correct dimension. I've read in this forum that per section IX, cast iron is not considered weldable for the purpose of building a pressure-retaining system. Where can I find this information in ASME IX?

Also UCS-56 (f) says: Weld repairs to P‐No. 1 Group Nos. 1, 2, and 3 materials and to P‐No. 3 Group Nos. 1, 2, and 3 materials and to the weld metals used to join these materials may be made after the final PWHT but prior to the final hydrostatic test, without additional PWHT...

For P‐No. 1 Group Nos. 1, 2, and 3 materials,the repair area shall be preheated and maintained at a minimum temperature of 200°F (95°C) during welding.

The manufacturer only used 80ºC. They say that buildup is not a repair procedure and that the table UCS-56-1 should be used instead. Also, they say that the builup is not made after the final PWHT, once the cast iron doesn't contain any welds, so none PWHT was made. Is that acceptable?

 

[metengr]

First, design code is not ASME Section XIII, there is no such code book section to date (there will be one for Pressure Relief Devices in the future).

Second, cast iron is weldable under certain precautions. Section IX is for qualification of welding procedures and operators, and is not applicable to limiting materials.

Section VIII, Div 1 Table UCS-56 is for pressure vessels fabricated of carbon steel, and not cast iron.

You seem to be trying to cherry pick information from ASME B&PV Code to suite your cast iron weld repair. Not really applicable here.

Go back and inquire the following information;

1. What filler metal was used for the weld build-up?
2. Was a WPS used for the repair? Ask to review it.
3. Ask if any nondestructive testing was performed of the build-up.

The answers to 1-3 above will decide if this was acceptable or not.

 

[weldstan]

Have you mistyped XIII for VIII? If so the manufacturer's statements regarding the use of UCS-56 to the repair of cast iron is erroneous. If they used a low carbon steel filler metal to make the repair, reject the casting.

 

[bruv]

ASTM A216 WCC is NOT cast iron - it is a weldable grade of carbon steel. (ASTM A216 = Standard Specification for Steel Castings, Carbon, Suitable for Fusion Welding, for High-Temperature Service).

I am a confused about the PWHT. Was the part heat treated after welding or not? If yes, then all should be OK. If not, then it is up to you to decide if it should be, according to your own requirements and specifications.

 

[weldstan]

My bad. Took the OP's cast iron quote instead of the looking at quoted ASTM steel casting spec.
If repair area is subject to cyclic loading, I would not accept it unless the part was subject to a stress relieving PWHT. It is assumed that the manufacturer had an appropriately qualified WPS.

 

[boorishjam]

Thank you all for the answers.

I'm sorry. I made some mistakes.

It's ASME VIII, and its carbon steel, but the part was manufactured with sand casting. No welded was necessary. That's why they say that no PWHT was made.

The part was not PWHT. It was only used a preheat of 80ºC.

The part is subject to cyclic loading, it supports the the kaplan blades bronze bushings.

The problem is that the code is not clear if builup is considered repair. The manufacturer says that the preheat is necessary only for welded joints.

 

[weldstan]

While ASME VIII would normally not apply to rotating equipment, it has been made applicable through Contract. SA-216 should apply as to repairs by welding stated therein. Regardless of Code or Specification requirements which are minimum requirements for normal service, the service requirements of this part should govern any repair methodologies used. Residual welding stress may well lead to service failure in cyclic loading conditions and this stress should be reduced as much as possible to assure greater lifetime operation.

 

[metengr]

The build-up to restore dimension is considered a weld repair, period. Regarding PWHT, in situations where cyclic loads are encountered as mentioned by weldstan, PWHT may indeed be prudent to ensure removal of harmful residual stresses and to reduce hardness of the base material heat affected zone.

Your best bet would be to simulate weld build-up on a coupon and see if the hardness and weld repair are acceptable for your application. Was a qualified WPS used? Was NDT performed??

 

[boorishjam]

Thank you.

A qualified WPS was used and magnetic particle inspection was performed.

The base metal average hardness is 132HB and the buildup area is 200HB.