UG-37, Area A1

[SnTMan]

Well, I'm having a bit of disagreement with my software.

Is there any circumstance where it is not permitted or is improper to use the second expression in Fig. UG-37.1 for A1?

The case in question involves opening reinforcement in a flat head when restricting the limits of reinforcement, for which my software seems to disregard the second expression, which yields the larger value of A1. It only outputs one value for A1 so it is impossible to know what it calculates for the other. Thanks, programmers.

I'm kind of of the opinion that, since the second expression does not involve "d" it is not modified when the limits are restricted. I suppose it could be reduced by the ratio of the restricted limits to the permitted limits ("d"), but in this case it still yields the larger value for A1.

I'm wondering if there might be an interpretation to the effect that the second expression for A1 be disregarded under some circumstances.

Any takers?

Regards,

Mike

 

[trottiey]

What do you mean by "restricting the limits of reinforcement"? UG-40(b) provides two alternate limits of reinforcement, and that's what the two alternate equations represent. But as far as I can tell, you could use the second expression wherever the first one applies.

I did find VIII-1-83-359, although I don't know if it's relevant to your design:
Question (1): For the calculation of A1 in UG-37, is tn = 0 when a pipe nipple is screwed into a flat head a distance which is not the full thickness of the head?
Reply (1): Yes.

 

[SnTMan]

trottiey, it is fairly common, at least in my line of work, to restrict the limits of reinforcement when a nozzle is located such the Code permitted limits would encroach on a discontinuity such as a corner joint, body flange, or my case at hand, the bolting of a flat, bolted head.

The programs I normally use will allow a user to specify a lesser limit of reinforcement both in plane and up the nozzle neck. This in turn reduces the contribution of excess material in the shell (A1) and in the nozzle neck (A2).

Regards,

Mike

 

[trottiey]

OK, I think I understand what you're doing. But now I tend to agree with your software. When you restrict the limit of reinforcement in plane, that should restrict both alternatives. So in the two expressions for A1, neither "d" nor "2(t+tn)" could be greater than your space restriction.

 

[SnTMan]

trottiey, thanks for your ideas. Not sure yet, more thought in order.

Regards,

Mike

 

[SnTMan]

Well, no mystery here, just some simplified algebra.

To document, if anyone is interested

Both expressions for A1 are identical except for the first term, which represents the limits of reinforcement as stated in UG-40(b).

Since the material inside the opening is not available for reinforcement the dimension along the wall either side of the opening can be written as either (2 * d - d), which reduces to d, or as 2 * (Rn + tn + t) - d, which reduces to 2 * (tn + t) since d = 2 * Rn.

If restricting the limits, the restricted limit, call it Dr, presumably replaces the larger of 2 * d or 2 * (Rn + tn + t) such that the first term for A1 becomes (Dr - d) and the larger expression for A1 still governs.

I say presumably because I haven't checked a large number of cases, but it seems reasonable.

Regards,

Mike