Can forged bar be used to make a forged valve? 5

[marklobo]

A section of forged bar per ASTM A350 LF2 is used to make a valve body. I was told by a forging supplier that the body could not be claimed to be a forging. OK, but then if the valve body is marked "A350 LF2", would that not imply it was made from a forging, since A350 is by nature a forging specification? Please see thread177-142661 on this subject.

 

[PeterIgg]

ASTM A350 and ASTM A105 are themselves quite clear as to what parts you can and cannot make from forged bar, ref section 4 - Manufacture. Without knowing the size of valve or geometry of the body you are querying it is difficult to say more. Have a look at the specifications and I think that you will be able to answer your own question.

 

[marklobo]

ASTM A 350/A 350 - 04a para 5.3.3 states "Except for flanges of all types, hollow, cylindrically shaped parts may be machined from rolled bar or seamless tubular materials provided that the axial length of the part is approximately parallel to the metal flow lines of the stock. Other parts, excluding flanges of all types, may be machined from hot-rolled or forged bar up through and including NPS4." Is a wafer-type valve body, with flange facings machined on the ends, a member of the family of "flanges of all types"?

I'm looking for some assurance that we will not be challenged when we claim the body is forged when it is made from material sliced from a forged bar. This is particularly disturbing, as per ASTM A 788-06 under para 3.2.1.2 "Discussion — Because of differences in manufacture, hot-rolled, or hot-rolled and cold-finished bars (semi-finished or finished), billets, or blooms are not considered to be forgings." Does the specification intend that the material sliced from forged bar be re-forged in order for the body to be made from a "forging" in compliance with A 350?

 

[JLSeagull]

Consider qualifying what you plan to provide within the quotation or the vendor documentation submitted for approval.

 

[Sircrashalot]

I've often sold valves made of barstock material up to 6" ND for the offshore market. Depending on the material used, some clients require that we conduct additional impact tests to verify that the strength of the material meets the required specification in both the transverse and logitudinal directions.

The manufacturer's that I've used for these valves are always very clear though to point out that the valves have been manufacturer from Barstock, and I would make sure that you are clear to your client as well.

Barstock is a great way to get valves in exotic alloys fast!

Andy

 

[kenvlach]

Re "Can forged bar be used to make a forged valve?"

No (unless you forge it afterwards), it is a machined valve. Selling it as a forging is not only unprofessional, it is criminal.
You just happen to be using forged billet as barstock.

 

[marklobo]

kenvlach's input causes this subject to take an interesting turn. Though ASME B16.34 does not specifically preclude the use of forged bar to make a valve body, MSS SP-25 requires that the material designation be on the body. The "criminal" act would be the false impression given by "A105" on the body that it was machined from a forging. Per B16.34-2004 4.2.2(d), marking the body "A105 BAR" could be a way to allow compliance, and make the use of forged bar "legal". Anybody care to challenge this approach?

 

[kenvlach]

Machining from forged & otherwise hotshaped material per A105 & A350 is only permissible for hollow cylindrical parts that do not break the metal flow lines of the forged material. Machining a valve would require some cutting perpendicular through the metal flow lines. A105 & A350 expressily forbid machining tees (which require the same sort of cutting as valve bodies) from bar stock.

The valve is only legal for sale as a non-forged item. Using "A105 BAR" on it is playing with semantics and unethical.

Cheers,
Ken

 

[marklobo]

The restrictions in ASTM A350 5.3.3 and A961 6.1.1 (referenced by A105) do not contstrain the detailed machining of parts. The requirements are there to assure good design practice, which is to align the direction of greatest tensile strength of the material with the principle stresses induced structurally or by fluid pressure. Further, and more significantly, the specifications are intended to prevent principle stresses from being induced in a direction other than that confirmed as compliant by tensile testing.

 

[kenvlach]

Given the possibility of fraudulently labeled 'forged' valve bodies, I suggest that purchasers require the S1. Macroetch Test given in ASTM specs. for forgings to verify proper metal grain structure (flow lines).

 

[marklobo]

When a custom-fabricated, unique valve makes S1 impractical, I strongly recommend proof testing and certification per the BPV Code, UG-101. This would confirm the applicability of the material type and form as accurately marked on the product.

As recommended by earlier posts, it is critical to make all material requirements explicit in the valve specification. Which leads leads me to conclude that the answer to my original question is, in a word, no.

 

[arunmrao]

To reiterate once again,machining from a bar stock does not qualify it to be a forged valve. This issue was raised about 10 years ago,while I was a casting supplier and during my visit I was shown valve bodies(< 2") machined from bar stock as forged valves. These had higher pressure rating and were for critical applications. I advised the manufacturer the difference and demonstrated it by macroetching for the flow lines . This practice was then immediately stopped.


Machining from bar stocks provides a quick and effective means to produce valves especially in difficult to cast alloys.

 

[metengr]

I am absolutely surprised that not one person has mentioned to have marklobo review ASME B16.34 and ASME/ASTM SA/A 350. Using the example cited in the OP, I can see why marklobo has asked the question.

ASTM A 350 LF2 is listed in ASME B16.34 Table 1 as supplied in two product forms - forging and bar. The key words are "product form" in this Standard. A forging is a product form, and bar is a product form that can be machined into a final product form, but it is NOT a forging product form.

At this point, one has to go back and review the specific material specification, in this case it is ASTM/ASME A/SA 350.

As stated in Scope 1.1, This specification covers forged flanges, ring rolled flanges, forged valves and fittings...
(note the following)....Although this specification covers some piping components machined from rolled bar and seamless tubular products (see 4.3.3), it does not cover raw material produced in these product forms.


Following the reference cited to 4.3.3 in SA 350 it so states,

4.3.3 Except for flanges of all types, hollow cylindrically shaped parts may be machined from rolled bar or seamless tubular products provided that the axial length of the part is approximately parallel to the metal flow lines of the stock. Other parts, excluding flanges, may be machined from hot rolled or forged bar through and including NPS 4.

So, as defined in the Scope of ASME SA 350, forged valves are specifically mentioned or singled out as a product form and, as such, does not imply that product forms can be machined from forged bar and be called forgings.

Thus, forged valves cannot be supplied as forgings from machined, forged bar.

 

[JohnBreen]

Hello all,

Metengr has hit the nail quite precisely on the head. I totally agree with his comments. Applying the rules of the ASME B31 Pressure Piping Codes, a valve body machined from a forged bar (product form) is not a forged valve body. Not withstanding the material at issue, the manufacturing process by which the component is made must comply with a Standard listed in Table 126.1 or 326.1, else it is an unlisted component.

As to the application of such a valve (unlisted component) to a B31 piping system, that would require qualification in accordance with paragraph 104.7.2 or 304.7.2. It might be so qualified, but it cannot be termed a "forged valve body".

Of course, all the above is just my opinion and NOT the opinion of ASME and NOT the opinion of any ASME B31 Pressure Piping Code Committee.

 

[marklobo]

I very much appreciate all the input on this subject. Many of the responders have refered to industry standards, and I believe we have revealed that interpretation of some requirements can be difficult.

What I find interesting is that none of the responders has answered the original question: "if the valve body is marked "A350 LF2", would that not imply it was made from a forging, since A350 is by nature a forging specification?". In my post of 28 Feb 07 18:50, I offered to translate the responses, with "no", which struck some raw nerves. Maybe my phrasing was bad, so let me re-phrase the question so any responder can come back with a one-sentence response to close out this thread:

If A350 LF2 barstock material is used appropriately to make a valve body, how should the body be marked?

 

[JohnBreen]

Hello again all,

"if the valve body is marked "A350 LF2", would that not imply it was made from a forging, since A350 is by nature a forging specification?".

The marking would imply that the component was machined from a piece of bar stock that was made to the requirements of ASTM A350 LF2. The marking would not mean that the component was a forged valve body in the Code usage of that term.

"If A350 LF2 barstock material is used appropriately to make a valve body, how should the body be marked?"

I know of no Code, Standard or regulation that would dictate or mandate ANY marking on such a component. Perhaps "Made in XXX" would be appropriate.

Conditions of procurement and sale are generally stipulated by Contracts. Such contracts are liable to the opinions of judges and juries in civil litigation. Clearly, if a contract stipulates that a valve that includes a forged body (as defined by consensus Codes) be provided as a deliverable under the terms of the contract, the valve body that is machined from a piece of forged barstock would not satisfy the terms of that contract.

"I believe we have revealed that interpretation of some requirements can be difficult."

Codes and Standards are mandated by various jurisdictions as part of their "Codes of Regulations" (i.e., laws). This is the only thing that gives Codes and Standards the force of law. Opinions provided in this discussion are the opinions of individuals. I would suggest to you that if you require a interpretation of something addressed by a Code you should submit an official inquiry and get an official interpretation from the full committee (then it would have the force of law). As an example, if you feel that there is something in ASME B31.3 that is vague or ambiguous, you should submit an inquiry to the B31.3 Code Committee using B31.3 Appendix Z as a guide. I can assure you that the ASME Codes Committees make every effort to provide an unambiguously worded document.

Regards, John.