REDUCE BORE CRITERIA IN ASME B16.34 2

[skengg]

Hi Guys,
i want to know is that there is any clause or detail in B16.34 Valve design standard which talk about reduce bore of valve. we want to design reduce bore Cast steel globe valve. but i need standard supprotive proof which allow us to reduce seat flow bore 90% of inside dia. at valve end.

 

[Danlap]

Hi,

ASME B16.34 is mainly for pressure/temperature rating. ASME B16.5 is about Pipe flange and flange fittings.
I think you're looking for API 602, which is about steel gate, globe and check valves for sizes NPS4 and smaller. It contains wall thickness and minimum bore criteria, among others.
'Standard bore' written in API 602 refer to what we know as reduced bore. Full-bore is full bore.
Quote' 5.2.2 The minimum cross-sectional area requirement for the standard bore flow passageway applies for both the valve body ports and the seat opening in the absence of the valve disc. The minimum flow passageway crosssectional area shall not be less than that obtained using the diameters in Table 3.' Unquote

Cannot snip the table due to proprietary rights of API.

Regards,
D

 

[skengg]

Thanx Danlap for your Response.
Although i know API 602 is mainly use for reduce bore valves. But i want to design valve as per B16.34. Actually i am looking for statement in which B16.34 allows to reduce flow bore max. 90% of valve end inside dia. there are several standards which have written this statement , But i couldn't be able to find this statement or Clause in B16.34.

 

[Danlap]

Hallo,
I didn't realize this before.
Check ASME B16.34 para 6.1.2, available on both 2013 and newest 2020 version.

Quote
6.1.2 Inside Diameter. For the purpose of determining
wall thickness, tm, using Table 3A or Table 3B, or the equations
in Mandatory Appendix VI, the inside diameter, d,
shall be in accordance with the following requirements:
(a) The inside diameter, d, shall be the minimum
diameter of the flow passage but not less than 90% of
the basic inside diameter at the valve end subject to
the considerations listed in (b) through (f).
Unqoute

Not sure what is your gain on this, but goodluck.

regards,
D

 

[skengg]

Thanx Danlap,
as shown in Clause they say "subject to the consideration listed in (b) through (f)" in which there is no mention of globe valves. its only know about ball valves. i am still confuse that can we reduce flow passage max. 90% in Cast Globe valve or not?

 

[Danlap]

I am not part of ASME committee and unfortunately interpretation of ASME B16.34 is only available for 1996 and older version. Point (b) to (f) indeed do not mention single body Gate,Globe,Check valve. However in our industry I don't think it is wise to based our design and its attributes solely to one standard.
6.1.2 main intention is to govern minimum wall thickness by constraining bore diameter. One can argue that, for other types (single body GGC) it is also applicable as long as the wall thickness requirement is still met.
In addition to as long as ID of flange gasket is also similar or bigger than ID of valve's flange bore, so that gasket is not protruding on flow path. It happened several times that the inner winding got 'curled'.
Not sure about the correlation with globe valve Cv (some detail process engineer prefer to have more or less same Cv of globe valves even from different supplier), but from my understanding reduce bore gate valve is more favorable for press-in seat design.

Maybe other practitioners in this forum have different view.
Regards,

 

[skengg]

Thanx Danlap for sharing information

 

[bcd]

ASME B16.34-2020 does not define reduce bore diameters for valves. The minimum bore diameter can be whatever you want it to be unless it is limited by some other product standard such as ISO or API. The 90% limit in B16.34 is only for the determination of minimum wall thickness. You cannot take a valve with DN 200 end connections but only a DN 50 bore and have the minimum wall thickness for DN 50. The minimum wall thickness cannot be less than that required for 90% of the DN 200 end connection. This is what paragraph 6.1.2 in B16.34 is stating.

 

[skengg]

Thanx bcd.
i understood now.