Inspection Template for Ellipsoidal head
Inspection Template for Ellipsoidal head
(OP)
We made ellipsoidal head refer to an acceptable approximation of a 2:1 ellipsoidal head (one with a knuckle radius of 0.17D and a spherical radius of 0.90D).
What is the of inspection template which shall be used? Using true shape of ellips 2:1 or shape with a knuckle radius of 0.17D and a spherical radius of 0.90D.
Thanks before.
What is the of inspection template which shall be used? Using true shape of ellips 2:1 or shape with a knuckle radius of 0.17D and a spherical radius of 0.90D.
Thanks before.





RE: Inspection Template for Ellipsoidal head
RE: Inspection Template for Ellipsoidal head
RE: Inspection Template for Ellipsoidal head
Then we order that head to sub-vendor, but sub vendor request R crown and R knuckle sizes, so we inform sub vendor that R Crown is 3150 mm and R Knuckle is 595 mm (Refer to UG-32(d) that an acceptable approximation of a 2:1 ellipsoidal head is one with a knuckle radius of 0.17D and a spherical radius of 0.90D).
When we simulate both head sizes on CAD, and found that on knuckle size has big different over 30mm between them, knuckle size of Approximate ellipsoidal smaller than True Ellipsoidal head.
UG-81(a) said that the knuckle radius shall not be less than that specified.
So, if our sub vendor make exactly the same sizes with approximate ellipsoidal head and we inspect the head using true shape of ellipsodal head, it is be out of tolerance, isn't it?
The answer is:
1. We change our design calculation for head using Appendix 1.4(d) Torispherical head. Is it correct?
2. then we check that head using Approximate ellipsoidal template. Is it correct?
Thank you.
RE: Inspection Template for Ellipsoidal head
I'm not sure what you mean by the knuckle radius on a true elliptical head. A truly elliptical head does not really have a knuckle (seems like ASME defines a particular radius as the "knuckle" portion, though, but that is arbitrary). The radius varies continuously from crown to tangent line. No two points have the same radius. This could be a problem drawing or interpreting your CAD drawing.
RE: Inspection Template for Ellipsoidal head