Stellite on ball

[samsarani]

Dear Friends
We have one order from my client to supply ON/OFF valve from size 4 up to 24 inch. Application is highly sour (H2S and CO2 and water and also a little CL). Material that costumer is ordered is A186 F6a for ball and also request for fully stellited of ball. I asked with some ball valve manufacture for fully stelliting of ball but they didn’t accept and do stelitting only contact area (areas contact between ball and seat ring). They don’t consider high corrosive media that cause SCC on ball. My questions are as follow:
1- What are manufacturer‘s limitation for apply stellite overlay on ball?
2- Is there another method instead of stelliting that cover corrosion and erosion concerns?
Please note that fluid is produce in well and these valve are used in wellhead facilities. Also rating of these valve are 1500#
I ask for specialist on this subject to help me to able correct decision.
Thanks all
SAM

 

[Scotsinst]

The valve body (and bonnet if it is top entry) and stem are pressure retaining and require to be supplied per NACE.
The ball is not pressure retaining and not strictly required to conform to NACE. Of course if it is closed for long periods the face of the ball will be under pressure and this part is stellited.
It makes sense to stellite the area in contact with the seats but not all of the ball.
I don't remember any reference to Stellite in NACE MR0175 ISO 15156.
Maybe some corrosion expert can help.

 

[superweo]

Dear Sam,
the issue is not due to the service.
The real problem of applying stellite on the ball is that it gests exfoliated after a while.
For this type of application on ball valves Tungsten carbide coating, applied with HVOF method, is technically better.
But if the service is really highly corrosive, then they should change the ball material to SDSS or Inconel.
Moreover if the service is that corrosive, what about the body material?
You should forsee a welding overaly in Inconel on the static and dynamic areas at least.

Ciao

 

[samsarani]

Thanks for your replies

Is it consider stellite overlay on ball as increase hardness and wearing coating protection also for corrosion protection?
In this stage I understand some coating company confirm full stellite on ball up to size 8 inch and don’t apply it for 8inch and above but I don’t understand what their restriction is.
If we have restriction to use stellite on ball for 8 inch and up, can we use inconel overlay on ball at first and then use tungsten carbide with HVOF method on inconel as wearing protection.

Thanks

 

[superweo]

If you want the most cost-effective solution you can do like TOTAL requires i.e. Carbon steell trim + 75 microns ENP + 400 microns of tungsten carbide coating.
Doing that you avoid the use of expensive materials and you have a corrosion and wearing protection on the trim.

Ciao

 

[samsarani]

Thanks for valuable reply
But please consider we had bad experience from HVOF method for tungsten carbide. Because some solid particles that flow up from well caused to have damage on hard faced (tungsten carbide) ball. With this result customer decide to change hard facing method from tungsten carbide to stelliting welding overlay. With discussion some ball manufacturer, we understand most of them apply stellite on ball up to 8 inch and don’t recommend it for 8 inch above (I don’t why and for what reason). And ordered ball valve are 10, 18,24 inches.
Because we have high corrosive media I suggest a layer inconel 625 on ball at the first and tungsten carbide on inconel 625 as second protection. But I don’t this way is applicable or not? And is there another safe method?

Thanks
Sam

 

[superweo]

Sam,
if you have particles coming from the well that damage the surface of the ball, you will not solve the problem by changing the base material in inconel.
If you have this kind of problem stellite is even worst!!!!
Anyway, I remain with my suggestion of CS trim + ENP + TC coating.

Ciao

 

[samsarani]

Dear Cio
Your knowledge and experience is perfect, I want to say you two things and I am going to clarify it with you and guide me.
1- Please consider base material of ball is A186 F6A and my suggestion was inconel 625 weld overlays on ball (A186 F6A) and use tungsten carbide on inconel.( not base material inconel 625)

2- Please if is possible for you send me some evidence , fact and figure for your suggestion(ENP+ tungsten carbide) for comparison with other method ( stellite and inconel over lay ). Some information for comparison these method with together ( hardness and corrosion and ….)

Thanks
SAM

 

[superweo]

Dear Sam,
regarding point 1, if you are going to overaly the ball with inconel, then why you use F6 as base material?
You can easily use carbon steel which is less expensive.
Regarding point 2, I do not have evidence to send you but I suggest you to check TOTAL specification PVV 142 on the paragraph concerning valves for severe service (Class E).

Ciao

 

[samsarani]

Dear Cio

I understand your correct concern completely .thanks
I don’t have Total specification which you mentioned in later recommendation (PVV142). Could you please send it to me?)

Thanks
SAM

 

[superweo]

Dear Sam
have a look at it.

ciao

 

[samsarani]

Dear Ciao

Thanks for your help and submitting. You really guide me and I appreciate for all.
Best regards
SAM