thread repair on valve body casting 1

[valvemania]

Hallo,

I have a valve body (Material ASTM A217-WC6) which has got 10 x 1" threads to fix the bonnet on the top. However during manufacturing, the hole for the threads were drilled too deep and it entered the body gallery.

My question: How can I close the hole and at the same time save the casting and the thread? The valve is designed to ASME.

thanks for your quick response.

 

[hsbcn]

Can you send some photos of the damaged parts?

My focus: Alloy Valves in duplex, super duplex, alloy 20, monel, inconel, incoloy, hastelloy, titanium, 904L, zirconium and uranus Valve Stockist Valvulas

 

[valvemania]

I sadly dont have a picture, but I have attached a rough sketch. the sketch on the left shows the current situation where the hole is penetrating into the gallery. And on the right you can see how the hole should actually be.

 

[pennpiper]

Send it back to the manufacturer and tell them to replace it.

prognosis: Lead or Lag

 

[jbeckhou]

did this happen to all 10 holes?

Petrotrim Services

http://www.petrotrim.com

 

[jwhit]

Do you have access to the inside which would permit you to weld repair from the inside? That is provided there is a qualified weld procedure to make the repair. If so, you might be able to plug the hole(s) with a threaded copper plug of the correct depth and weld from the inside after opening up the improperly threaded area. There may be a little clean up required in the bottom of the hole, but it may be worth a try. Preheat (300-400f) and interpass (600max) controls are in order for this material as is a PWHT, which could be done as a local PWHT. ER80S-B2 would be a good filler metal choice. I'll let the code experts weigh in on the legitimacy of doing this type repair.

 

[pennpiper]

You do not say where you are or where this project is located but it really does not make a difference.

You have gotten advice relative to returning the valve to the manufacturer for replacement and you have gotten advice on self repair.

Now lets say you do go ahead and repair the valve and put it into service. Later this valve fails for some reason even unrelated to the repair. Three maintenance workers were killed and another three were seriously injured. Injured enough that two of them will never work again.

The post accident investigation uncovers that the valve which failed was modified in the field prior to installation. The investigation further uncovers that this repair was not done by the original manufacturer or with their approval. This discovery of an unauthorized repair therefore invalidates the original manufacturers warranty on the valve and throws ALL of the legal and financial responsibility for the deaths and injuries onto your company and by association onto you and the other people who did an unauthorized repair.

Could this happen? Yes! Would this happen? Do you really want to chance it?

With that said, I repeat my original recommendation; Send it back to the manufacturer and tell them to replace it.

prognosis: Lead or Lag

 

[valvemania]

dear all,

thank you for your advice. This is a water/steam valve with operating temp at 300°C. This valve was in service for 6 years now. End user only recentyl noticed that steam had been comming out of 2 of the 10 holes.

As this valve has to go back into service, we are trying to make a quick fix.

@jwhit: the inside of the valve body can be accessed thru a 250mm diameter hole. I am not quite sure whether this is sufficient to access the damaged holes. But according to ASME Section II "The casting shall not be peened, plugged or impregnated to stop leaks" this means that the weld repair you suggested is not applicable right?

@pennpiper: I understand the your concerns regarding the repair. I would however would like to know the options I have for repair before sending it to the foundry where this valve was purchased.

 

[jwhit]

Plugging isn't the same as welding, the copper plugs are removed after welding and serve only as a non-stick backing material in the root of the weld. Weld repair is regularly done to WC6 castings and if done properly is as good as, or often, better than the surrounding base metal. That is why I stated "qualified weld procedure". A 250mm hole should be more than enough to access the bolt holes. If you were to do an ammonium persulfate etch on that casting you would probably find a number of weld repairs made by the foundry that produced the casting. ASTM A217 and ASME SA217 outline some of the parameters for repair and ASME IX provides the qualification information required to make the repairs. My uncertainty with making the repairs is unfamiliarity with the applicable requirements after the part has been in service. I do recall in the past seeing castings that have been repaired for some reason or other after time in service, so it comes down to the governing code.

 

[gerhardl]

This must be worse than even Pennpiper thought! I am sure you have already decided not under any circumstances to put the valve back without certified repairs and the factorys' guarantee, or a completly new correctly certified valve.

Chances are that even when filled with bolts and screwed down with nuts, you might get, or already have had, cavitation conditions through the threaded holes. Recently found leakages indicates worsening conditions over time.

300 deg centigrade equals between about 80 and 90 bars in my steamtable, a steampressure giving reason to be careful.