1 1/4 Cr - 1/2Mo YIELD STRENGTH

[bam8888]

I am trying to design a TEMA BEM fixed tubesheet exchanger per ASME Sec. VIII, Div.1 with the following criteria:

Design Temp. = 1150°F
Metallurgy = 1 1/4Cr - 1/2Mo [plate (SA-387-11 Cls. 2), tubes (SA-213-T11), & Forgings (SA-182-F11 Cls 2)]

The problem I am running into is trying to interpret ASME Sec. II part D, Table Y-1. Although the material is allowed up to 1200°F, yield stresses are only listed up to 1000°F. However, I need the yield strength of the tubes, tubesheets, and shell cyl. at 1150°F to complete the UHX tubesheet calculations.

How can I find the values for yield strength at 1150°F? Does the code mention how to procede and if so where is it referenced?

Your help is greatly appreciated.

 

[stanweld]

Why are you even contemplating using these materials at that design temperature? The material is in the high temperature Creep regime for design; yield strength is not germane to the design. You truly need to reconsider materials selection.

 

[SnTMan]

Per Part UHX 13.3 "When a yield strength value is not listed in Table Y-1,one may be obtained by using the procedure in UG-28(c)(2) Step 3"

Regards,

Mike

 

[bam8888]

Thanks for your help. Unfortunately, I can't change the material at this stage (budget quote). I tried to suggest alternates, but the customer is not interested at this time.

 

[TJOrlowski]

Agree with Standweld, I'm not sure why you're using this material either.

Allowable stress around 1,900 at your design temperature? Save yourself and your customer some time and take a look at another material.

347/347H comes to mind.

-TJ Orlowski

 

[Guest102023]

Agree with Stanweld et al; this is out of the range for 1¼Cr-½Mo.

 

[MJCronin]

bam-bam.....

Another teeny tiny point....

A TEMA BEM for 1100+ degrees F ???/? I don't think so....

TEMA BEM is good to a maximum of ~ 300F

Aside from your client's poor choice of materials, he has a very poor choice of HX design.

Ya, ya I know.....you are running out of time and you have to bid the spec.....your boss is an MBA...

 

[DSB123]

MJC
From your reply it would appear that you have come across the same "numpties" out there with MBA's. It's a pity they have the ultimate say in decision making as they tend to get it wrong on the majority of times.

 

[davefitz]

Certainly the wrong material and wrong design.

But anyhow, I remember seeing the fixed plate design dwgs for the clinch river liquid sodium HX ( never commissioned), and as I recall, the tubes were twisted, en masse, to allow some flexibility for thermal expansion, shell vs tubes, during transients. Exactly how is your design going to accomodate differential expansion during transients?

A beter design would be similar to "header type" heaters, with tubeside fluid distributed / accumulated in internal headers, and the tubes able to move slightly relative to each other , also add thermal sleeves at the header to shell connection. Tubing would be T23 or T91/92, but if T23 tubes are used, the tube stub at the header would need to be another alloy ( non bainitic) if teh heder wall thickness was greater than 1" .

 

[SnTMan]

I have personally designed a similar unit some years ago, similar metallurgy, similar temperatures, as specified by the customer. Not my preference, certainly, but it can be done.

Regards,

Mike

 

[SnTMan]

Afterthought: that WAS before Part UHX was introduced.

 

[Guest102023]

DSB123 & MJCronin,

Its not all bad with MBAs. As a failure analyst I thank them daily for my job security.

 

[davefitz]

brimstoner;
careful now- it would be an MBA who would decide to outsource your job overseas.