AppletonBowen
Mechanical
Good morning All,
I have been a long time user/reader of Eng-tips, and 99% of the time my question has been answered satisfactorily by using the 'search' function! However, I have a question regarding the design of fastener sets in ASME VIII Div. 1. I am reasonably new to ASME VIII Div.1 but not new to Pressure Vessel design (european codes). As you may be aware, ASME is prescriptive in terms of material selection (II-D) whereas the EU codes require PMAs to be done as part of the designer's responsibility.
Typically, I when designing bolted connections, I will specify a similar grade of material for both stud and nut. I.e. both SA-540 B23/24 Cl.1 or SA-193 B16 are the two primary bolting materials I use currently.
However, as part of the routine review of designs before I joined, I have noticed that in some applications, the SA-193 bolting is not sufficient. Substituting to SA-540 satisfies the calculations, but I am not sure if I will need to replace the nuts as well. Having done shear calculations on the threads and compressive stress calculations for the nut footprint/CSA, the lower allowable SA-193 is satisfying the code.
Has anyone got any experience using dissimilar materials for bolts and their nuts? All threads are coated with low friction/corrosion resistant coatings. Is there some guidance in any of the ASME Codes regarding the design of nuts, as I can only really see bolting guidelines in VIII-1. I suppose my primary concern is that upon loading, the bolt & nut will have different stress/strain rates causing unexpected thread interface pressures (potential galling?)
Any pointers would be greatly appreciated!
I have been a long time user/reader of Eng-tips, and 99% of the time my question has been answered satisfactorily by using the 'search' function! However, I have a question regarding the design of fastener sets in ASME VIII Div. 1. I am reasonably new to ASME VIII Div.1 but not new to Pressure Vessel design (european codes). As you may be aware, ASME is prescriptive in terms of material selection (II-D) whereas the EU codes require PMAs to be done as part of the designer's responsibility.
Typically, I when designing bolted connections, I will specify a similar grade of material for both stud and nut. I.e. both SA-540 B23/24 Cl.1 or SA-193 B16 are the two primary bolting materials I use currently.
However, as part of the routine review of designs before I joined, I have noticed that in some applications, the SA-193 bolting is not sufficient. Substituting to SA-540 satisfies the calculations, but I am not sure if I will need to replace the nuts as well. Having done shear calculations on the threads and compressive stress calculations for the nut footprint/CSA, the lower allowable SA-193 is satisfying the code.
Has anyone got any experience using dissimilar materials for bolts and their nuts? All threads are coated with low friction/corrosion resistant coatings. Is there some guidance in any of the ASME Codes regarding the design of nuts, as I can only really see bolting guidelines in VIII-1. I suppose my primary concern is that upon loading, the bolt & nut will have different stress/strain rates causing unexpected thread interface pressures (potential galling?)
Any pointers would be greatly appreciated!
