Navigating ASME B16.34 3

[CB90]

Hi,

I'm a trainee engineer in the oil & gas industry.

I was wondering, if i have a valve with valve body = 'LTCS', Seat and Disc = 'Duplex 22% Cr'. Which material do i use when determining the class of valve (special or standard) in B16.34 Table 2?

 

[LittleInch]

LTCS sounds like Low Temperature carbon Steel. This designation is too vague to be of any use and you need to find out exactly what material it is. Body material is your material for working out pressure rating, based on the class of the valve,, not the internal trim and seat material. Class rating is normally stamped on the valve plate or the valve body somewhere (150, 300, 600 etc). You normally find data like this in the valve list for a site. I think (hope) you've not phrased your question correctly as the class is predetermined by the flange and body rating, but the actual wax working pressure is governed by material, and design temperature.

My motto: Learn something new every day

Also: There's usually a good reason why everyone does it that way

 

[CB90]

Thanks for the quick response LittleInch.

Basically i've been asked what the NDE requirements are for a valve. I've checked the datasheet to see what materials the valve is constructed from (as above post). However when I check ASTM B16.34 to find out if the valve is special or standard (to determine NDE requirements) i'm not sure whether I should be checking against the body or seat materials.

 

[MJCronin]

Have you talked, informally, with some of the manufacturers of this type of large valve ?

(B16.34 covers flanges larger than 24" NPS)

This question might be better answered if posted in the eng-tips Valve forum......

You may find your answer in this superb magazine.....

http://www.valvemagazine.com/

MJCronin
Sr. Process Engineer

 

[bcd]

To determine the Class per B16.34, you use the valve body material. But LTCS is not a material description in B16.34. The class number should be marked on the valve body as well. 150, 300, 600, etc. If not, then you may not have a valve that was designed and built per B16.34. Is there a manufacturers name plate? Best option is to ask the manufacturer.

 

[TGS4]

CB90 - whether or not the valve is standard or special depends on the level of NDE. Basically, if you want to take credit for the higher working pressures for the Special Class, then you need to perform the extra NDE specified in Section 8.

A valve is not special or standard until the NDE extent has been done - and not the other way around.

Does that make sense?

(MJCronin - you're thinking of B16.47 - B16.34 is the right specification for this discussion).

 

[CB90]

BCD- Thanks thats what i was after, wasnt sure which material governs which part of B16.34 i should check. (I checked the materials certs, the body is A350 LF2. The class is 1500)

TGS4- I hadn't realised this. I thought the type of valve, standard or special, depended what level of NDE you perform. Maybe i was going about this the wrong way. The steps i took were as follows:

1. Check max design temperature and pressures of the valve
2. Check materials of construction (I used the valve body as governing mat'l, but wasn't sure hence the thread)
3. Check rating
4. In B16.34, table 2 - Read across from temperature and down from rating to make sure max design pressure was less than the figure in the table
5. Pressure was below that in the 'Standard' table therefore I concluded the valve had no specific NDE requirements.

 

[CB90]

Sorry TGS4 ...

*Determined what level of NDE you perform

 

[TGS4]

CB90 - you were going about it the wrong way. The markings on the valve are very specifically explained in Section 4 (and 4.2.3 specifically). If you just have a class rating, then the valve is assumed to be standard. Otherwise it may be marked with a specific rated pressure and temperature.

So, check the markings on the valve first.

You are correct though that the valve body (think of it as the pressure-retaining part) governs the material Group.

 

[CB90]

Ok. Thanks for your responses and guidance! Great help.