BALL MATERIAL FOR VALVES 2

[ligin18]

Hi All

As per datasheet for pipeline ball valve(API 6D) ,the ball material is UNS S32750(SDSS). Only material grade is mentioned in datasheet. One Vendor is offering bar material(A276) for the ball but other vendor is offering forged material (A182 F53).As my understanding bar stock has a higher risk of porosity and flaws over forged material. Plz give more details for bar material Vs forged type.

Vendor is proposing 3 piece design instead of 2 piece design for ball valve. Plz clarify which one is better in design as well as price.

 

[metengr]

How large is the ball valve? Bar material is limited in size for certain pressure retaining application in valves because of the possible alignment of inclusions, depending on how the bar material has been worked. There should be no porosity, however. Depending on the ball size, bar could work in this application.

 

[arunmrao]

I thought balls were cast, it was only the very small(<25mm diameter), that were machined from bar stock.

"Even,if you are a minority of one, truth is the truth."

Mahatma Gandhi.

 

[EdStainless]

Balls from bar should be fine, the hole should be passing down the length of the bar where there is the greatest risk of internal defects. In truth bar that has been warm or cold rolled, or even extruded can be called forged, there is a lot of slack in many of the specs. Internal defects in forgings are possible also, so they aren't necessarily better.

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P.E. Metallurgy, Plymouth Tube

 

[metengr]

In truth bar that has been warm or cold rolled, or even extruded can be called forged..

Absolutely do not agree.

 

[EdStainless]

In many specs that is true, in some it is not.
You have to know the details of the specs.

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P.E. Metallurgy, Plymouth Tube

 

[metengr]

It boils down to a specified minimum work reduction ratio and near net shape between rolling and forging processes. If your specification addresses neither of these for rolling or forging, the specification is toilet paper.

 

[EdStainless]

But some specs give required reductions, but aren't clear about how you do it.
This is both good and bad.
In many cases there is no practical issue, as the extruded part will have the same structure and properties as an open die forging. But in cases of alloys that develop strong preferred orientations it can be an concern.


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P.E. Metallurgy, Plymouth Tube

 

[SJones]

Don't cross post. You have a number of replies in another forum which now creates difficulties.

Steve Jones
Corrosion Management Consultant

http://www.linkedin.com/pub/8/83b/b04

All answers are personal opinions only and are in no way connected with any employer.

 

[ligin18]

Hi

Ball Valve is 16" full bore valve design for 150#

 

[metengr]

You want a forging or casting.

 

[ligin18]

we used forged material for valves trim.But for this project vendor is offering bar material for ball other are forged material. Plz clarify the disadvantage of bar over forged material for 16" full bore 150# ball valve

 

[metengr]

Bar of that size will not be worked through thickness, like a forging, and could have stacked inclusions which upon machining could open to the surface. Even a cast ball would be acceptable.

 

[EdStainless]

It depends on how the bar was made, it may well be forged from a cast ingot at that size.
The better question is what NDT are they doing on the ball? That is the issue with any product form.
Also ask about the heat treatment, all superduplex should be tested to ASTM A923 B or C to assure proper anneal.
A part this size would require annealing after it is bored.

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P.E. Metallurgy, Plymouth Tube

 

[arunmrao]

Valves are considered as commodity products and are highly price sensitive . Machining a 16 inch hollow ball from a solid stock, just does not gel commercially for 150 class valve.
I have cast several balls of this size, and they are well received.


"Even,if you are a minority of one, truth is the truth."

Mahatma Gandhi.

 

[EdStainless]

Agree, for 16" casting is the fastest way there.
My main concern would still be metallurgical condition, not manufacturing process.
These alloys are very easy to HT wrong, and the resulting corrosion resistance is very poor.

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P.E. Metallurgy, Plymouth Tube