## UCS-66(b) Reduction For SA-106 Gr. B

## UCS-66(b) Reduction For SA-106 Gr. B

(OP)

I have performed a calculation with Advanced Pressure Vessel software which says I can take the UCS-66(b) reduction for a lower MDMT. Is this correct (assuming 3/8" Tn and E* of 85%)? There are no calculations printed in order to verify that they are correct. The link is to the calculation sheet

## RE: UCS-66(b) Reduction For SA-106 Gr. B

Sometimes using this reduction not allowed. Check eng specs also.

## RE: UCS-66(b) Reduction For SA-106 Gr. B

Thanks for responding. The thing that has me concerned is the fact that SA-106 Gr. B is not listed in Fig. UCS-66 under curves "B", "C", or "D". Therefore, you would have to use curve "A". Unless I am using Fig. UCS-66.2 incorrectly, I'm coming up with a ratio of .9078. Using Fig. UCS-66.1, that ratio is subsequently not giving me the reduction I need for curve "A". I need this vessel to be designed for an MDMT of -49 deg. F. If this material won't work, can anyone lead me in the direction I need to be in?

Thanks in advance!!

## RE: UCS-66(b) Reduction For SA-106 Gr. B

Curve "B" applies to SA-106-B. I don't think you could rate SA-106-B to -49°F MDMT. Try SA-333-6.

## RE: UCS-66(b) Reduction For SA-106 Gr. B

I did the calculation by hand, and I'm still not getting by with it. UsingFig. UCS-66.2, I'm coming up with the following:

tr E*/tn – c = (.2598)(.85)/(.312-.125) = .22083/.187 = 1.18

If I'm calculating this ratio correctly, SA-333 Gr.6 won't work either. Can someone confirm that my calculations aren't totally out of whack?

Thanks again!

## RE: UCS-66(b) Reduction For SA-106 Gr. B

doct9960 is right, Curve B applies for pipes(Fig UCS-66 Note(2)(c) ) So you have -20°F without impact testing and UCS-66(b) reduction.

all values taken from your calc. rep.

ratio = (0,2881x0.7)/(0.375-0.125) = 0.80

with the ratio calculated above you can reduce MDMT without impact testing 20°F approx. so your MDMT=-40°F

looks like you have no chance to rate your pipe(SA-106-B) -49°F without impact testing. again doct9960 is right :)

you have two options.

1) impact tested SA-106-B. (see UG-84)

2) using SA-333Gr6(same allowable stress value at375°F)

I would prefer the second option.

## RE: UCS-66(b) Reduction For SA-106 Gr. B

Correct one

ratio = ((0.2881-0.125)x0.7)/((0.375*0,875)-0.125) = 0.562

so you get ~50°F reduction. you have no problem with SA-106-B.

again sorry for the mistake,

## RE: UCS-66(b) Reduction For SA-106 Gr. B

EJL

## RE: UCS-66(b) Reduction For SA-106 Gr. B

Keep in mind that the MDMT and MAWP are related to each other. As you decrease the MAWP, you decrease the coincident ratio, thus decreasing the MDMT.

Let's assume that the vessel MAWP is limited by the shell with the following conditions:

design pressure = 200 psi

design temp. = 375°F

design MDMT = -49°F

joint efficiency = 0.85

corrosion allowance = 0.125"

shell material = SA-106-B (14" STD pipe)

MAWP = S x E x t / (Ro - 0.4t) = 17100 x 0.85 x 0.203 / (7 - 0.4 x 0.203) = 426.46 psi

Now let's calculate for the rated MDMT for three different cases of MAWP.

Case 1: MAWP = 426.46 psitn = 0.375" x 0.875 = 0.328"

Unadjusted MDMT = -20°F (Curve B)

tr = MAWP x Ro / (S x E + 0.4 x MAWP) = 426.46 x 7 / (17100 x 0.85 + 0.4 x 426.46) = 0.203"

Coincident ratio = tr x E* / (tn - c) = 0.203 x 0.85 / (0.328 - 0.125) = 0.85

From Fig. UCS-66.1, temperature reduction = 15°F

Adjusted MDMT = -20 - 15 = -35°F

Since the adjusted MDMT of -35°F is warmer than the design MDMT of -49°F, you need to impact test or change material.

Case 2: MAWP = 350 psitn = 0.375" x 0.875 = 0.328"

Unadjusted MDMT = -20°F (Curve B)

tr = MAWP x Ro / (S x E + 0.4 x MAWP) = 350 x 7 / (17100 x 0.85 + 0.4 x 350) = 0.167"

Coincident ratio = tr x E* / (tn - c) = 0.167 x 0.85 / (0.328 - 0.125) = 0.699

From Fig. UCS-66.1, temperature reduction = 30°F

Adjusted MDMT = -20 - 30 = -50°F

Rated MDMT = -50°F (no impact test required)

Case 3: MAWP = design pressure = 200 psitn = 0.375" x 0.875 = 0.328"

Unadjusted MDMT = -20°F (Curve B)

tr = MAWP x Ro / (S x E + 0.4 x MAWP) = 200 x 7 / (17100 x 0.85 + 0.4 x 200) = 0.096"

Coincident ratio = tr x E* / (tn - c) = 0.096 x 0.85 / (0.328 - 0.125) = 0.402

From Fig. UCS-66.1, temperature reduction = 92°F

Adjusted MDMT = -20 - 92 = -112°F

Rated MDMT = -55°F (per UCS-66(b)(2))(no impact test required)

As you can see, MDMT decreases as MAWP decreases. If you still want to use SA-106-B without impact test, you need to rate your vessel with an MAWP that will satisfy the design MDMT of -49°F. This is assuming that your vessel MAWP and MDMT is governed by the SA-106-B shell.

## RE: UCS-66(b) Reduction For SA-106 Gr. B

Locally, A333-6 is readily available and has a very small cost premium over A106-B.

## RE: UCS-66(b) Reduction For SA-106 Gr. B

If I'm using the calculations with the new MAWP correctly, my adjusted MDMT would be as follows:

Case 4: MAWP = 395 psi

tn = 0.375" x 0.875 = 0.328"

Unadjusted MDMT = -20°F (Curve B)

tr = MAWP x Ro / (S x E + 0.4 x MAWP) = 395 x 7 / (17100 x 0.85 + 0.4 x 395) = 0.188"

Coincident ratio = tr x E* / (tn - c) = 0.188 x 0.85 / (0.328 - 0.125) = 0.787

From Fig. UCS-66.1, temperature reduction = 22°F

Adjusted MDMT = -20 - 22 = -42°F

Since the adjusted MDMT of -42°F is warmer than the design MDMT of -49°F, I need to impact test or change material.

The other materials that are on this vessel are SA-234 Gr. WPB and SA-105, so the design is governed by SA-106 Gr. B & SA-234 Gr. WPB which are both 17,100 at this temperature.

Thanks for Everyone's help on this!

## RE: UCS-66(b) Reduction For SA-106 Gr. B

If it were me, I'd switch to SA333-6 (pipe), SA350-LF2-Class 1 (flanges), and SA420-WPL6 (fittings).

The cost of this would be less than conducting impact testing on alternative materials.

## RE: UCS-66(b) Reduction For SA-106 Gr. B

Would I be correct in assuming that by using SA-333 Gr. 6 pipe, SA-350 LF2 Class 1 flanges, and SA-420 WPL6 fittings for the vessel, then postweld heat treating the vessel, per UCS-68(c), I would get a 30 deg. F reduction which would put me @ -50 deg. F?

This seems like the easiest way to go if it is true.

Thanks in advance!

## RE: UCS-66(b) Reduction For SA-106 Gr. B

Regards,

Mike