Hello all. Is there a limitation on how much you can miter a 45 elbow?(e.g. you can miter a 45 into a 30 but can not miter a 45 into a 20). I was asked this question and was told they were working under api1104, I glanced at 1104 but did not find anything. Maybe I skippe over it or if anybody knows if it’s in a different code/standard. Thanks in advance.

I'm curious about this too.
I don't know the answer.
Next week I should see some of the locals gas company inspectors and will try to ask.

I've cut down more that a few fitting to make some odd angle turn.
It could be that the problem would be the inside welds would be too close together and heat input in that narrow area too much.
Or the two inside welds are touching at some point.

I can't recall ever needing to just make a 20 degree turn.
There is a bit of no mans land area there where its not enough angle to cut down a fitting, to great an angle to bend pipe, or not enough length for pipe to comfortably bend, or cheat the fit a bit (not that I would ever do that).

But I have had to turn more than 90 degrees at least once, a 90 plus a cut down 90 or 45, whatever was available.

Floyd

I was able to talk with a local gas company inspector. We are talking API 1104, the code that the high and mighty here seem to sometimes sneer at.
The inspector said that the procedure was the inside (throat) welds could not be closer that 1 inch.
So it would depend on the size of the fitting.

As for as the chart that jarsnab supplied, the second link, I have my doubts.
I did not look at all but for instance 4inch pipe @ 15 degrees.
The chart say 2 5/32 for the OUTSIDE arc, and 3 1/32 for the INSIDE arc. Nope!
The outside has to be greater than the inside. Some of the other numbers don't seem right either.

I've always used a percentage of the angle and have not had much issue with the inside diameters not matching,
within 3/32 hi lo.

By percentage I mean;
If I have a 90 and need to make a turn of only 75 degrees I divide 75 by 90 and get 0.83.
I want to use 83% of that 90.
Lets just guess that the outside stretch out of a 4 inch 90 is 13 inches. 13 times .83 is 10.79.
So mark at 10.79.
Inside stretch out (also a guess) is 6 inches. 6 time .83 is about 5 inches. Mark that on inside stretch out.
Cut the fitting thru those points, grind a bit and tack it up.
The above mentioned chart shows that exact procedure. I've just generated the numbers by a percentage of the angle.

With a standard fitting and relative thin wall pipe, one can and or needs to bevel the inside of the fitting, or use a pup transition .

Floyd