Your interpetation of B31.1 para 122.1.7(B)(B.1)

[brandonb73]

I know this is a piping code, but I posted this question here because it applies to Boiler External Piping.

In the above mentioned paragraph, it states: "The stop valve or cock shall comply with the requirements of (C.5) below."

para (C.5) states: ..."valves or cocks shall be bronze, cast iron, ductile iron or steel."

Question: since only the stop valve is mentioned, does that mean I can use a stainless check valve per para 107.1 as long as the material is listed in table 126.1?

 

[metengr]

brandonb73;
Not so fast. The Code does not provide card blanch for materials to be used in any environment or service just because materials are listed in Table 126.1. The reference to C.5 applies to low temperature/pressure boilers and if a stop valve is installed of the permitted materials, the check valve should be close to the same material. Why would you want to install a stainless steel check valve? Galvanic corrosion could be a problem.

Have you heard of stress corrosion cracking in austenitic grades of stainless steel at around 160 deg F and higher in oxygenated, treated water?

 

[JohnBreen]

Generally speaking (not meant as a reply to the question you posted) it may be of some value to you to look through the National Board of Boiler and Pressure Vessel Inspectors archive of classic technical articles. There are more than 70 technical articles available here:

http://www.nationalboard.org/TechnicalArticles.aspx

Only one of which is:

http://www.nationalboard.org/Index.aspx?pageID=192

There are many grades of stainless steel that are intended for special applications. You must know how the particular SS fits into the environment in which it will be asked to perform.

Regards, John

 

[GenB]

no you can not use stainless by just assuming
check valves are included (the first check), you can use ss as the second!
will taht helps?
B31.1 works with Sect I as BEP see that sect I does not accept stainless for wetted surfaces other than gageglass fixtures.
genblr

 

[brandonb73]

Gents, my original question was simply one of "is this material allowed by the code"? But since a concern about the design has been raised, lets explore that a little more.

metengr.....bronze valves are commonly used for this application. Am I incorrect in saying that SST is less corrosive when used with carbon steel pipe than bronze?
With respect to stress corrosion cracking, properly treated boiler feedwater should not contain a high concentration of oxygen or chlorides due to deaeration, oxygen scavengers and phosphates.


GenB.....This is boiler external piping. Per PG-58.3, "materials, design, fabrication, installation and testing shall be in accordance with ASME B31.1, Power Piping."

 

[GenB]

brandonb73
I use it every day.
Sect. I tells you the B31.1 limitations.
For me: B31.1 is part of Sect. I
You should look at sect. I as well.

they are both in your back when it come to compliance.
You may ask your AI or field Inspector.
note that after BEP the Jurisdiction takes over and decides what materials are to be used.


gageglass fixtures are boiler proper, you are alolowed alloy. I should haven't mentioned.
Bronze is only allowed to certain pressure.
SS even if water can be clean, is not allowed. Sect I will not take the chance to let the mfr/user choose process or clean water.

 

[brandonb73]

"Sect. I tells you the B31.1 limitations."

If I am reading the 6th paragraph of the Preamble (Sec I) correctly, it says that materials, design, fabrication and testing of BEP are contained in B31.1. NOT SEC I.


"For me: B31.1 is part of Sect. I".

If you mean: assigned technical responsibility by (as stated in both Sec I and B31.1), then I agree, but B31.1 is a separate Code and not technically part of Sec. I

"SS even if water can be clean, is not allowed. Sect I will not take the chance to let the mfr/user choose process or clean water."

Then please explain why PG-9.1 lists SA-213 and SA-182 (which are stainless steels) as acceptable materials for boiler parts?

 

[metengr]

brandonb73;
I would not recommend austenitic stainless steel in low pressure feedwater systems because of the concern for stress corrosion cracking. This is a cautionary note that is obvious in Section I and the reason is that any cold working performed on the stainless steel can result in local residual stress that will initiate SCC in an aqueous environment at elevated temperature (its not necessarily the chlorides, studies have shown SCC in high purity feedwater at or above 160 deg F).