Ligament efficiency - reg.,

[VIJAYANSA]

Hi all,

As per UG-27 (c)(1), E stands for joint efficiency or ligament efficiency, whichever is less to be used.

My questions are,

1) While modelling the vessel in PV elite, The software doesnot consider about the ligament efficiency for nozzle holes, why???

2) In asme sec viii div 1, UG-53, There is no provision for calculating circumferential efficiency????

3) If I have the logitudinal efficiency is 0.9, Circumferential efficiency is 0.7, diagonal efficiency is 0.65, longitudinal joint efficiency is 1 and circumferential joint efficiency is 1, Out of these which one can I consider to design the vessel by using UG-27 (c) (1) formula.

This question may be basic, But I need more clarification....

Sorry for my bad english.

VIJAYAN S A

 

[prex]

1) Nozzle holes follow the rules for opening reinforcement, no ligament efficiency need be considered
2) UG-53 provides rules for calculating the efficiency of longitudinal, circumferential and diagonal ligaments. The longitudinal ligament efficiency is equivalent to the efficiency E for longitudinal joints, the efficiency of diagonal ligaments is transformed into a longitudinal or circumferential one by the rules in UG-53
3) As UG-27(c)(1) formula is for circumferential stress and longitudinal joints, you need to calculate the equivalent longitudinal efficiency of diagonal ligaments, compare it to the efficiency of longitudinal ligaments and take E as the lower of the two.

prex
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[VIJAYANSA]

Thanks prex,

Against point 2,

Fig. UG-53.5 & Fig. UG-53.6 are correspondingly drawn between the diagonal efficiency Vs Longitudinal Efficiency and Equivalent longitudinal efficiency vs angle of diagonal with longitudinal. From this two graphs, how can I transfer the diagonal ligament into equivalent circumferential ligament???

And, For Converting diagonal ligament into equivalent longitudinal ligament, Fig. UG-53.6 enough... What's the use of Fig. UG-53.5??? If you say, for converting diagonal efficiency to Longitudinal Efficiency and vice versa, in which formula can we use the diagonal ligament???

VIJAYAN S A

 

[prex]

See examples in L-8.4 and L-8.5, they might help you. You should also try some various limiting examples.
The point is that when the circumferential ligament efficiency may be controlling over the longitudinal efficiency (this requires the longitudinal pitch to be 5 times the circumferential pitch or more), then the diagonal ligament will substantially be a longitudinal one (small θ angle) and only the reduction in longitudinal efficiency resulting from fig.UG-53.6 will be of interest.
With your figures the efficiency of diagonal ligaments is higher than the efficiency of circumferential ligaments from Fig.UG-53.5, so you only need to check the equivalent long.eff.of the diag.lig from Fig.UG-53.6.

prex
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