Vessel design temp over 900F 1

[Spoonful]

Hi All,

ASME VIII Div 1 UG-20(d) states below:

(c) Design temperatures that exceed the temperature
limit in the applicability column shown in Section II, Part
D, Subpart 1, Tables 1A, 1B, and 3 are not permitted. In
addition, design temperatures for vessels under external
pressure shall not exceed the maximum temperatures given
on the external pressure charts.

Where the max temp on table 1A 1B are 900F,
here we got design a vessel to 550C, material: A335 P11

Dose anywhere in ASME saying this is acceptable to go over the limit?
In ASME B31.3 same material was allowed for a lot higher temp.

Thanks in advance
Regards
Spoonful

 

[metengr]

No, you cannot exceed the maximum service temperature limit for material in design applications. You cannot cherry pick information between ASME code book sections. You follow the specific code book rules based on original design requirements.

 

[MJCronin]

The P11 is only acceptable in a narrow temperature range.

It is also prone to long term creep damage and has been replaced in older power plants

OMHO, for a few bucks more, consider use of the higher alloy A335 Type 22 material

 

[stanweld]

1 1/4 Cr-1/2 Mo alloy steel would be the wrong choice for 550 C. Follow advice of MJCronin.

 

[jtseng123]

I don't think 1 1/4Cr-1/2Mo is a wrong choice for 550C and under. Many big companies including ours are using that material for that temp range. We only use 2 1/4Cr-1Mo in high temp hydrogen service such as hydrocracking reactor.
I just finished a big reactor with 1 1/4Cr-1/2Mo at 550C not in hydrogen service.

 

[darshiva]

I think that the maximum temperature under Sec I or Sec VIII is 1200 F, not 900 F. 900 F is where the creep (time-dependent properties) starts and some considerations shall be taken regarding elastic-plastic analysis for peaking in welds, tubes and tubesheets. You can design for this temperature and comply with the code.

Once said this, it is not advisable to go beyond 1000-1050 F.

 

[metengr]

Yes, the maximum permitted service temperature for SA 335 P11 is 1200 deg F. Time dependent properties start at 900-950 F for this grade of pipe, where creep effects are considered in determining the allowable stress value in Table 1A, Part D.

The Code does not provide guidance for optimum selection of material for service. It provides guidance for materials that are not permitted because of obvious limitations, which pose a threat to safety. Material selection for an application should be based on knowledgeable individuals that understand damage mechanisms in materials and steer clear of them.

Regarding use of Grade 11 material. I would not use this material for high energy piping systems because the availability of SA 335 Grade P22 is typically greater and lower cost (because of availability) . If I had to use P11, I would have my own design temperature in high energy piping systems at 980 deg F continuous exposure, with a maximum of 1,000 deg F for periodic steam temperature overshooting during plant operation. This temperature has been proven to be comfortable for long term performance.
Other process applications may warrant use of Grade 11 plate or tubing at higher temperature. This is up to the designer. I would not exceed 1025 deg F as my own choice unless periodic monitoring or surveillance is performed to evaluate creep damage.

 

[Spoonful]

Hi All,

Thanks for all the comment, any guidance on where to start on the creep analysis?

Regards
Spoonful

 

[darshiva]

You may start taking a look to WRC 470.

 

[MJCronin]

http://hghouston.com/Resources/Disc...orumid/5/postid/4201/scope/posts/Default.aspx

http://www.eng-tips.com/viewthread.cfm?qid=113879

Everything comes down to money......sooner or later....

P22 gives you a little extra margin for those operator thermal excursion mistakes...... P91 is even better material (used all over Europe)

How comfortable are you with the thermal control of the process ?