A SMALL MISTAKE IN COMPRESS.

[SJEC]

I am working on a new vessel with 30" dia and 1380 psi @ 180F. The above pressure actually choosed by B16.5 pressure-temperature rating.

I am try to use standard B16.47 on girth flange and receive a warning say the MAWP of 600# flange is 1376 psi.
However, 24" B16.5 flange MAWP will be 1384 psi from Compress.

I have checked B 16.5 and B16.47 pressure-temperature table. They are identical. Therefore, It muse be compress is using different interpolation method between B16.5 and B16.47.

Tom, Could you check it for me? Thanks

 

[xema77]

Do you have a liquid level above the girth flange? Sounds as though it is reducing for static head.

 

[SJEC]

No Liquid Level to be consider now.

 

[TomBarsh]

Is this really a mistake in COMPRESS? Or is this due to some other reason?

Let us consider the 2008a Addenda for the moment. Per Section VIII Division 1, UG-44, flanges produced to ASME standards B16.5 and B16.47 may be accepted as standard pressure parts, using the listed pressure-temperature ratings. Great!

Now we refer to Table U-3 for the "Year of Acceptable Edition of Referenced Standards in This Division" as per paragraph U-3. The Table indicates that the 2003 Edition of B16.5 is accepted, and that for B16.47 the 1996 Edition is accepted.

Oh-oh, isn't there a 'new' 2006 Edition of B16.47? Yes, there is, but it is not approved for use in the 2008a Addenda (blame the Section VIII committee, if you must). Consequently, COMPRESS uses the 1996 Edition of B16.47 for vessels designed to the 2008a Addenda.

In fact, COMPRESS uses the Editions of B16.5 and B16.47 specified in Table U-3 for the Edition/Adenda selected for the Section VIII Code in COMPRESS. As you change Editions/Addenda in COMPRESS (going back to 1995) the corresponding Edition of the flange standards is used.

Generally, B16.5 and B16.47 provide the same pressure-temperature ratings for the same class material. But there may be (and are) some small variations in pressure-temperature ratings for different Editions of the same standard. Thus, there are some slight differences between the 1996 and 2003 Editions of B16.5, as well as similar differences between the 1996 and 2006 Editions of B16.47.

Note the difference in pressure ratings for A105 material in the two Editions of B16.47 (similar differences exist in B16.5).

100° F 200° F
1996: 1480 1350
2006: 1480 1360

Because different Editions of B16.5 and B16.47 are accepted for the 2008a Section VIII Division 1 the result is that the two flange size ranges may obtain different pressure ratings for the same material.

I'll let you perform the same exercise for the 2009b Addenda.

Now the 2010 Edition is out and I see that Table U-3 still imposes the 1996 Edition of B16.47.



Please note the description on the main page of this forum: "Codeware sponsors this forum for peer-to-peer discussions regarding the COMPRESS ASME pressure vessel design software. We invite COMPRESS users to share their experiences on issues raised. Contact Codeware directly for technical support." I spend some time here providing free comments. But if there are questions, or it is believed that there are program errors, they are best directed directly to Codeware technical support (support 'at' codeware), or use the submittal form on our website Support page.




"Although this forum is monitored by Codeware it is not intended as a venue for technical support and should not be used as the primary means of technical support."

Tom Barsh
Codeware Technical Support

http://www.codeware.com

 

[SJEC]

Thanks Tom

 

[TomBarsh]

I should add for everyone's benefit, that, even better than blaming the ASME Code committee for long delays, etc, is to get involved. Get involved in the committee work. Volunteer. Join. Do something to help out. In the end it will be to your benefit.



"Although this forum is monitored by Codeware it is not intended as a venue for technical support and should not be used as the primary means of technical support."

Tom Barsh
Codeware Technical Support

http://www.codeware.com

 

[jte]

Looks as though Section VIII Subgroup General Requirements (and Subgroup Design) is working on updating the acceptable editions in Table U-3, including updating B16.47 to the 2006 edition. Hasn't been balloted yet, though.

I'll second Tom's comment on getting involved. The code committees work with volunteer labor.

jt