Looking for 1950 API-ASME Code Allowable Stress 1

[jtrobin]

I need to find the allowable stress for SA-285-C at 950 and 1,000 degrees F from the API-ASME pressure vessel code that would have been applicable for a vessel built in 1950. Also if the thickness formula for cylindrical shells is different from the ASME code I would need that also.

 

[Bobfromoh]

From the 1949 ASME Code:
950 F = 2600 psi
1000 F = 1350 psi

Shell: t=PR/(SE-.6P)
E= joint efficency for longitudinal joints
E= 1 for seamless shells

Heads: t=5PL/(6SE)
E=1 for seamless heads

Paragraph U-68, for complete radiograph, E=.95.
Paragraph U-69, otherwise (?) E=.8

Paragraph U-201(a), Vessels built to U-69, the allowable stress values may be multiplied by 1.25

......That's what I have.

 

[MJCronin]

Isn't this a carbon steel material that is not supposed to see a sustained temperature over 775F

What, exactly is this 60 year old pressure vessel doing at 1000 F ?

 

[jtrobin]

Thanks for the reponse, yeah I have the 1949 ASME code but allowable stresses in the API-ASME code are higher than the ASME code. I've found the allowable stress for A-70 in the 1943 API-ASME code, but A-285-C replaced A-70 in 1947. In the 1951 API-ASME code A-285-C stops at 900 F. The client no longer has the design calculations and we're trying to reproduce some of the calculations for them.

The process in the vessel operates at 950 F with some internal refractory lining. The client had some testing and replications done on the vessel metal which showed it to still be servicible. They have a new vessel on order but it will be some time before it is delivered and installed.

 

[Duwe6]

Take a thermal scan of the parts in question at while in normal operation. That will proove [or disproove] whether the refractory is keeping the metal below 775°F. If it is running above the Code limit, refuse to have anything further to do with it. Professional liability extends to Personal. Be a shame for you to lose your pension and [if you have one] vacation home.

 

[jtrobin]

Thanks, I've told them they should install some thermocouples on the vessel to get readings on the metal temperature.

We're not making any recommendations, just supplying some information to them.

I've seen a few vessel such as this one that were built in the 1940's that are still operating at these elevated temperatures. Though it may or may not be prudent to do so, since the vessels were originally stamped for these design conditions before the code changes that lowered the service temperatures for carbon steel they are still in service at these temperatures.

 

[MJCronin]

I agree with Duwe6....there is a risk being taken here

Much of the research and metalographic studies on carbon steel exposed to high tempertures has been done after these vessels were put into service. After long periods above ~800F, the carbon precipitates out of the structure and causes failure

Some good information about this:

http://www.hghouston.com/index.html

 

[petroPV]

is 775°F iimitation in VIII?

 

[petroPV]

Can anyone advise where 775°F limitation is listed in VIII? Thanks

 

[jtrobin]

There isn't a limitation of 775 F in VIII or in Section II. The allowable stress tables in Section II for most carbon steels stop at 900 F. The notes in the allowable stress tables in Section II for most of the carbon steels refer to the chance of graphitization occuring from prolonged exposure to temperatures above 800 F and the note references Nonmandatory Appendix A-240.

 

[Duwe6]

In other words, it is incumbent on the Owner/Operator to properly & regularly inspect these items. This a known mode of time-related deteriation caused by high temperatures, just like 'creep'. If they operate hot enough to cause a known defect mechanism, they are required by NBIC & API to inspect for those forms of deteriation.