How Low Can You Go With SA-105 Flange?
How Low Can You Go With SA-105 Flange?
(OP)
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.
Any feedback would be greatly appreciated.





RE: How Low Can You Go With SA-105 Flange?
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
RE: How Low Can You Go With SA-105 Flange?
RE: How Low Can You Go With SA-105 Flange?
Stress in tension, you may have an exemption here.
RE: How Low Can You Go With SA-105 Flange?
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
RE: How Low Can You Go With SA-105 Flange?
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.
RE: How Low Can You Go With SA-105 Flange?
RE: How Low Can You Go With SA-105 Flange?
RE: How Low Can You Go With SA-105 Flange?
RE: How Low Can You Go With SA-105 Flange?
Even though the components could be identical, the code governing thier use could possibly result in two different MDMT's.
EJL
RE: How Low Can You Go With SA-105 Flange?
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.