Formula for guided bend test Jig-diameter API %LC

[DiplingAndre]

Hello,
I've some problems withe the calculation Fig. 4 in API 5LC
The Formula is A = (1,15(D-2t)/(e-D/t-2e-1))-t
D is for example 16" or 406,4 mm
t = 0,204" or 5,2 mm
e = 0,1025" or 102,5 mm

I think that the formula is not correct coz i found in an old version (1991) A = (1,15(D-2t)/(e*D/t-2e-1))-t

But when I try to calculate i don't get realistic results.
What am i doing wrong?

 

[redpicker]

I see problems with that equation.

One, the variable e is the strain, and should be the same in either USC or metric units (it is a dimensionless variable). In your example, you are saying 0.1025" or 102.5mm, this should be 0.1025 in/in or 102.5 mm/m. If they are going to express the strain in mm/m, then the equation will have to change to accountt for this.

Second, looking at the denominator using the USC uints, (e-D/t-2e-1), D/t ratios are going to be very much larger than the strain values so this term will always be a negative value, which would produce a negative value of A.

You might want to ask your question to API. You can find information for this at

http://api.org/Standards/reqint.cfm

You will want specific in your question by stating you think you have found an error in specification 5LC, then stating what you have posted here.

rp