Multiple openings in flat head not reinforced by nozzles

[Pybou]

Hello there !

I need to design a flat head with multiple openings according to ASME VIII Div 1 and more particularly UG-36 and UG-39.

First of all, I determine the minimum required thickness of the flat head without opening using UG-34. Then I tried to calculate the openings.

I have 4 openings in the flat head (see attachements)

Do the openings need a reinforcement as per UG-36(c)(3)(-a)(-2) ?

Opening 1,2,3 respects the rules of UG-36(c)(3)(-a)(-2) --> these openings don't need reinforcement
Opening 4 : there are multiple diameters for this opening. So I calculated an equivalent diameter using Appendix 13-6 --> this opening need a reinforcement.

Do the position of the openings satisfy the rules of UG-36(c)(3)(-d) ?

Opening 2 and 3 : the distance between the two openings doesn't respect the rules of UG-36(c)(3)(-d) --> they can't stay unreinforced
Opening 3 and 1 : the distance between the two openings doesn't respect the rules of UG-36(c)(3)(-d) --> they can't stay unreinforced
Opening 1 and 2 : the distance between the two openings respects the rules of UG-36(c)(3)(-d) --> they can stay unreinforced

Conclusion : if I make a calculation of reinforcement for opening 3, openings 1 and 2 can stay unreinforced.

Reinforcement of openings 3 and 4
Below, there is a view of openings 3 and 4 that need to be reinforced.
From here, I don't consider opening 1 and 2 anymore as specified in UG-39(a).

UG-38(b) : the two openings diameters (equivalent diameter for opening 4) are less than one half of the diameter of the head
UG-38(b)(1) : my flat head have two openings --> not applicable
UG-38(b)(2) : the two openings diameters (equivalent diameter for opening 4) are less than one half of the diameter of the head and the average diameter of this pair is less than one-quarter of the head diameter. But the spacing is less than twice the average diameter but greater than 1.25 the average diameter. So I need to determine to area of reinforcement for each opening, sum them up abd distribute the area such that 50% of the sum is located between the two openings.

My questions
1 - Is it the good way to analyse this problem ?
2 - How do I calculate the reinforcement of the big opening as there is no nozzle welded on it but a flat head with another opening bolted on it ? Should I considered the other flat head as a welded nozzle ?
3 - UG-39(d)(2) indicates that I can also increase the head thickness instead of calculating the reinforcement area. Is it correct ?

Thanks in advance guys,

Best regards,

 

[prex]

1) Can't follow you when you say

Conclusion : if I make a calculation of reinforcement for opening 3, openings 1 and 2 can stay unreinforced.

Anyway this has no influence on what follows, as openings 1,2,3 appear to be equal and will have the same reinforcement.
2) Of course you can't take any credit for the cover on op.4: just calculate it as having no nozzle, hence no available reinforcement in the nozzle.
3) UG-39(d) is an alternative procedure with respect to UG-39(b): it is provided as a simpler approach, but should end up with a larger thickness.

prex
[URL unfurl="true"]http://www.xcalcs.com[/url] : Online engineering calculations
[URL unfurl="true"]http://www.megamag.it[/url] : Magnetic brakes and launchers for fun rides
[URL unfurl="true"]http://www.levitans.com[/url] : Air bearing pads

 

[Pybou]

Hi prex !

Thanks for your answer, I'm happy that this problem grabs your attention.

[EDIT] thread794-395350 grabs my attention and I think I made a mistake by using UG-36(c)(3)(-d).
Indeed :
- Openings 1 and 2 are 49.2mm diameter
- Opening 3 is 50 mm diameter
The spacing between them is enough to consider them as isolated as per UG-36(c)(3)(-c) ! But the spacing between them and the large opening is less than the sum of their diameters. But the large opening needs to be reinforced. So when I start to go through UG-39, should I only consider the large opening as UG-39(a) excludes openings that do not exceed size and spacing limits in UG-36(c)(3) ?

1) I said that because UG-36(c)(3)(-d) is applicable only for unreinforced openings. So if I reinforce opening 3, UG-36(c)(3)(-d) won't be applicable for opening 3. Openings 1 and 2 are then sufficently far from each other.

Can't follow you when you say

Conclusion : if I make a calculation of reinforcement for opening 3, openings 1 and 2 can stay unreinforced.

2) Thanks for the advice. So the only reinforcement area available will be the extra thickness of the head. I will use the equivalent diameter and the total thickness of the head to determine the limit of reinforcement. Does the method of equivalent diameter seem to be the good way to process from your point of view ?

3)Ok for UG-39(d). When you say "with respect to UG-39", does that mean UG-39(d) itself respects the rules of UG-39(b) ? Or does that mean the rules of UG-39(b) need to be respected and then we perform UG-39(d) ?

Thanks prex, I appreciate !

Bye.

 

[prex]

As "the spacing between them and the large opening is less than the sum of their diameters", then you need to check the reinforcement of all the openings.
The use of an equivalent diameter per 13-6 seems reasonable to me.
UG-39(d) (with Ug-39(e)) is an alternative to UG-39(b): you choose one of the two and forget about the other one.

prex
[URL unfurl="true"]http://www.xcalcs.com[/url] : Online engineering calculations
[URL unfurl="true"]http://www.megamag.it[/url] : Magnetic brakes and launchers for fun rides
[URL unfurl="true"]http://www.levitans.com[/url] : Air bearing pads

 

[Pybou]

UG-36(c)(3)(-c) specifies : "No two isolated unreinforced openings, in accordance with (-a) or (-b) above, shall have their centers closer to each other than the sum of their diameters". So, from my point of view, this is applicable only for unreinforced openings. But my large opening shall be reinforced so I don't have to take this large opening into consideration when I deal with UG-36(c)(3)(-c). What do you think about that ?

As "the spacing between them and the large opening is less than the sum of their diameters", then you need to check the reinforcement of all the openings.

Ok for the equivalent diameter method.
Ok for UG-39(b) or (d). I observe that when there is no nozzle, the method in UG-39(d) gives a lesser thickness than in UG-39(b).

 

[prex]

But , as you said,

Opening 2 and 3 : the distance between the two openings doesn't respect the rules of UG-36(c)(3)(d) --> they can't stay unreinforced
Opening 3 and 1 : the distance between the two openings doesn't respect the rules of UG-36(c)(3)(d) --> they can't stay unreinforced

so you need to check the reinforcement of all of them.
IMO you can't interpret the code in such a subtle way! BTW this is unrelevant as openings 1,2,3 are almost identical.
Also don't miss the last paragraph of UG-36(c)(3)(d).

prex
[URL unfurl="true"]http://www.xcalcs.com[/url] : Online engineering calculations
[URL unfurl="true"]http://www.megamag.it[/url] : Magnetic brakes and launchers for fun rides
[URL unfurl="true"]http://www.levitans.com[/url] : Air bearing pads

 

[Pybou]

Thanks prex for your answers ! Sometimes it's a bit complicated to read the code taking into account all the paragraphs.
In another thread which I follow carefully you wrote :

Let me try to rephrase everything as we (me included) made a bit of confusion:
1) As the opening CL distance is greather than 2.5/(d1+d2), per UG-36(c)(3)(d) you can't classify them as not needing a check of the reinforcement
2) So you need to check the reinforcement of all the openings
3) As the opening CL distance is greather than d1+d2, you can check their reinforcement as if they were isolated ( UG-39(b)(2) or UG-39(e)(1) )
4) Now you need to choose between UG-39(b)(1) and UG-39(d)
5) If you choose the former you'll certainly get a lower increase of the thickness (possibly nothing), also because you will profit of the material in the nozzle; however you'll have to check also against the last paragraph of UG-36(c)(3)(d) (unlikely to occur, remember that you don't need to take the available limit of reinforcement, but only what you need to get sufficient reinforcement)
6) With the latter everything is simpler, as you noted, you just calculate an increased thickness with respevt to the minimum required without openings

So the good way to process is :
[ol 1]
[li]Determine per UG-36 (c)(3) is the opening need a reinforcement or not[/li]
[li]If they don't need reinforcement, and if there are 3 or more openings that don't need reinforcement, we need to check that the distance between them is greater than 2.5(d1+d2). If so they can stay unreinforced, otherwise, they have to be reinforced.[/li]
[li]If they need to reinforced, we have to check that the distance between them is less than d1+d2 to consider them as isolated and use UG-39(b)(2) or UG-39(e)(1)[/li]
[/ol]

What confuses me the most is the fact that :
[ol 1]
[li]My point 3 above is applicable when "If they need to reinforced" whereas UG-36(c)(3)(-c) talks about "unreinforced" openings[/li]
[li]UG-39(a) starts by excluding all openings which respect UG-36(c)(3)[/li]
[/ol]

Can you correct my way of process ?

Thanks a lot for taking time for me.

 

[prex]

OK for the process 1-2-3.
UG-36(c)(3)(c) is there to exclude from the group of unreinforced openings those that do not meet the criterion, then you go to UG-39 to check the reinforcement: I don't see any conflict.

prex
[URL unfurl="true"]http://www.xcalcs.com[/url] : Online engineering calculations
[URL unfurl="true"]http://www.megamag.it[/url] : Magnetic brakes and launchers for fun rides
[URL unfurl="true"]http://www.levitans.com[/url] : Air bearing pads