Toriconical Sections.

Amitash · **Joined:** Tue Jun 14, 2011 7:31 pm **Posts:** 3

Hello Everybody,

Please advice me on the following :

Is it mandatory as per code to have knuckle portion for the conical section having half apex angle less than 30°?
As per UG-32(h) 'Tori conical heads or sections may be used when the half apex angle is less than or equal to 30deg and are mandatory for conical head designs when the angle alpha exceeds 30°, unless the design complies with 1-5(g).'
Also, when I see the PVElite output for conical section ( Where my alpha = 22.93° ), I find a 'Results for Discontinuity Stresses per Bednar p. 236 2nd Edition' which is required as per 1-5(g).

If 1-5(g) is applicable only for alpha more than 30°, can the calculation be ignored for alpha = 22.93°?

Javed Nasir · **Posted:** Sat Jun 18, 2011 3:29 pm

Joshi,

I see your point and have following comments.

1- 1-5(g) describes discontinuity analysis when half apex angle exceeds 30 degree for conical sections without having knuckle and with/without having added reinforcement.
2- Discontinuity analysis of 1-5(g) is not required for toriconical heads or sections of UG-32(h) even if half apex angle exceeds 30 degree.
3-No added reinforcement of 1-5(d) is required for the heads of UG-32(h).
4-To be declared a head of UG-32(h), it is required that knuckle radius shall be greater of 6% of outside head skirt diameter and 3 times the knuckle thickness.
5- Toriconical heads are prefered over conical heads in order to avoid discontinuity stresses.
6- It is recommended to use toriconical heads when P>300 psi, T>450F, MDMT colder than -20F, cyclic services.

Further feedback from any other member is requested.

Javed Nasir · **Posted:** Sat Jun 18, 2011 4:07 pm

Joshi,

See the following Interpretation to support point no. 2 above.

Interpretation: VIII-81-38
Subject: Section VIII - Division 1, UG-32 and 1-5(e)
Date Issued: June 30, 1981
File Number: BC-80-128
Related Documents:

Question (1): May the large end of a toriconical reducer, as shown in Fig. UG-36 sketch (b), with a knuckle that meets the requirements for rL and with a half-apex angle a greater than 30 deg., be designed using the formulas given in UG-32(g) and (h) only?

Reply (1): Yes.

Toriconical Sections.

Who is online