How Low Can You Go With SA-105 Flange? 1

[UW1981]

B31.3 and ASME Section VIII indicates SA-105 material(for a flange, in this case) has a MDMT of -20 F. However, B31.3 allows for some materials to be used as low as -155 F without impact testing (Table 323.2.2, note 3) provided the stress ratio does not exceed 0.3. The service is propane refrigeration (Normal Fluid Service). The question is whether or not "note 3" is applicable to SA-105 flanges? 'course, we'll need to make sure the bolts are good for the lower temp, too, if the flange is OK to -155 F.

Any feedback would be greatly appreciated.

 

[vesselfab]

actually what it says is that a105 b16.5 flanges are exempt from impact testing down to -20*F

you can use it much lower if the curves bear it out or if you use impacted tested material.

but for -155 I don't think so

for propane...if I remember correctly auto-refrigeration is about -50 or somewhere like that.

If it were me, I would choose 350-LF3 just for simplicity

 

[deanc]

After more thought....The best bet would be to follow vesselfab's advice.

 

[deanc]

See UCS-66,b

Stress in tension, you may have an exemption here.

 

[JoeTank]

deanc,
I don't have a Code book handy right now to check out UCS-66(b), but do you think it would apply here? Pipe flanges resist pressure and mechanical loads in bending, not tension.

Joe Tank

 

[TomBarsh]

You can operate B16.5 flanges down to -155° F MDMT per ASME Section VIII Div 1 if the conditions are right. However, there other materials that may be better suited for such cold service. In any case, the following rules apply:

UCS-66(c) specifies that B16.5/ & B16.47 flanges are exempt from impact testing when used at MDMT no colder than -20° F.

UCS-66(b)(1)(b) specifies that Fig UCS-66.1 (Reduction in MDMT without impact testing) "may also be used for components not stressed in general primary membrane tensile stress, such as flat heads, covers, tubesheets, and flanges (including bolts and nuts). The MDMT of these components without impact testing as determined in UCS-66(a) or (c) may be reduced as determined from Fig UCS-66.2."

Figure UCS-66.2 is a flow chart illustrating "UCS-66 Rules for Determining Lowest MDMT Without Impact Testing".

Thus the temperature reduction curve of Fig. UCS-66.1 can be applied to standard flanges to obtain ratings colder than -20° F. Per UCS-66(b)(2), impact testing is required for MDMT colder than -55° except as per UCS-66(b)(3) (exempts from impact testing down to -155° F if the coincident ratio is 0.35 or less...see UCS-66(b)(1)(b) for coincident ratio for flanges) and UCS-68(c) (a 30° F bonus reduction if nonmandatory PWHT has been performed).

To sum up this confusing set of rules: if there is some headroom between the design pressure and the flange pressure rating, then the MDMT rating can go down to -55° F without impact testing. If the "headroom" is sufficiently large, then the MDMT rating can go down to -155° F.

 

[JLSeagull]

Being conservative, I don't go below -20 degree F.

 

[dcasto]

Being practicle for propane refrigeration, I always use SA105 down to 13 psia propane (-50 F) with no impact testing. And I don't worry about -130F on my ethane lines during blowdown.

 

[UW1981]

Everyone....thanx for all the comments and advice. I believe you got me headed in the right direction to evaluate this application (putting an existing piping system) into propane service.

 

[eliebl]

One other item to note. In the vessel code the flange can have a lower MDMT based upon the stress ratio of the attached piping (UCS-66 (b)(1)(c)). The piping code does not have a similar paragraph. The reference is in figure 323.2.2B note (a)(2).

Even though the components could be identical, the code governing thier use could possibly result in two different MDMT's.

EJL

 

[gunnarhole]

You may want to review the paper at mahbsrv.jrc.it/downloads-pdf/ASTM_A_105.pdf before you make any final decisions about using A105 at low temperatures.

The Chemical Risks Directorate Federal Ministry of Employment and Labour in Brussels recommends that critical ASTM A105 pipe flanges, i.e. components containing hazardous substances and operating at temperatures lower than 0 °C, should not be used as intended without taking further precautions because of insufficient toughness due to the eventual presence of ferritic-pearlitic microstructures with a large grain size.