Use of ASME (SS 304) (SA240 Gr 304) material at 580 degree C

[gitsunil]

Dear Sir/ Madam,

We are designing a S&T Heat exchanger with following design condition:

Shell side: 0.21 Kg/Cm²(G) @ 455°C (MOC: CS)
Tube side: 4.5/FV Kg/Cm²(G) @ 580°C (MOC: SS304 as per process datasheet)

While designing this exchanger in recognized commercial software like COMPRESS & ASPENTECH S&T MECHANICAL, it prompt us to feed yield stress & “B” value as INPUT value of SS 304.

My query is as below:
As per ASME II-D, SA240-304 material can be used up to 816°C and allowable stress value also available up to 825°C (refer ATTACHMENT to this trhread).

However ASME code does NOT provide “yield stress” & “B” value (for external pressure cal) for SA240-304 mat at temp. 580° C. As such, query is, even though ASME does allow the SA240-304 upto 816° C but does not provided the “yield stress” & “B” (beyond certain temp, ~ 420°C) then from where to get these values at higher temp? or is there any restriction in use of SA240-304 under VACUUM condition up to certain temp only (upto where value of “B” value is provided ASME, ~ 420°C)?

Or shall we change the TUBESIDE material to some other GRADE of SS, which can withstand 580°C (under VACUUM)? Which could be this GRADE?

We would highly appreciate your guidance on this regard.

Best regards,
Sunil Agrawal
Static Equipment Department (STEQU)

Tecnimont Private Limited
(Formerly Tecnimont ICB Pvt Ltd)

 

[metengr]

Why would you need to use YS and B value for vacuum service conditions when the tube is pressurized? I would think using ASME Section VIII, Div 1 Part UHX would suffice.

 

[SnTMan]

gitsunil, assuming you are calculating a cylinder, 1) Referring to Chart/Table HA-1 there are A/B curves to 816 C. Any software should pick this up and perform the calc, but 2) it appears your component is of the ratio Do/t < 10, therefore B value and yield strength is needed.

UG-28(c)(2) gives the steps needed to obtain yield strength from B, which is obtained from Chart/Table HA-1. You can then enter the data into your software. Curious the software won't do that.

You should be fine with the 304.

Regards,

Mike

The problem with sloppy work is that the supply FAR EXCEEDS the demand

 

[metengr]

SnTMan;
My question is why is UG-28 calculation needed in this application when the tubes are under internal pressure? I could see if the shell side pressure was greater than the tube internal pressure.

 

[moltenmetal]

Above 1000 F you need to use the L grade stress values when using 304.

The alternative is to use 304H and use its stress values.

 

[SnTMan]

metengr
Assuming that the entire tubeside is subject to the vacuum condition, and unless a differential pressure design is used each side of the exchanger must meet the applicable design conditions, with the opposite side at both its design condition and at atmospheric. In this case the common elements (tubes, tubesheets, floating heads) are designed for the external (shell) pressure + full vacuum internal (tubeside), while elements that are not common, channel cylinders, heads etc. are designed for external pressure (vacuum) only. Part UHX considers the common elements, but not the "not common" ones.

moltenmetal
Not sure why you'd say that, I'm not familiar with any such requirement, am I missing it? Also Chart / Table HA-3 for 304L is limited to 800 F. Use of 304L for external pressure at higher temps is not permitted per UG-20(c).

Regards,

Mike



The problem with sloppy work is that the supply FAR EXCEEDS the demand

 

[Jano6924]

gitsunil:

I totally agree with SnTMan statements. UG-28(c)(2) gives the procedure to obtain B and yield when Do/t < 10. I’m also surprised to read that none of these programs can do such calculation automatically.

Yes, according to Fig. HA-1 (ASME-II-D) type 304 steels can be used for external pressure up to 815°C.

I have seen pressure vessels and heat exchangers data sheets showing one design temperature for internal pressure, and another design temperature for external pressure, I would recommend to read again current data sheet, if the only design temperature shown for tube side is 580°C then use it for both, internal and external pressure.

Regards.

 

[moltenmetal]

SnTMan- you're right- my comment was related to stress values listed in table A-1 of B31.3, whereas the OP's question was about Section VIII. B31.3 permits the L grade austenitic materials to be used all the way up to 815C with reduced stress values, but limits the use of the straight grade (higher) stress values to 1000 F- above 1000 F you can only maintain the "high" stress values if you have more than 0.04% carbon (i.e H grade).

Brain fart on my part- please ignore me and carry on...

 

[SnTMan]

moltenmetal no worries, all too easy to do

I seem to remember something about the 0.04% C limit in Sec VIII, Div.1 but could not find it yesterday...

Real or imagined?

The problem with sloppy work is that the supply FAR EXCEEDS the demand

 

[metengr]

It is in Section II, Part D, Table 1A , Note G12 At temperatures above 1000°F, these stress values apply only when the carbon is 0.04% or higher on heat analysis.

 

[moltenmetal]

OK metengr: good- I wasn't as far off as I thought I was!

 

[SnTMan]

Yes, and it does apply to many of the austenitics. A person needs to watch this.

Don't know why I couldn't see this the other day...

Thanks metengr

The problem with sloppy work is that the supply FAR EXCEEDS the demand