L/D Ratio and Instrument Nozzles

[Angsi]

Basic pressure vessel question I guess the following two is:

1. Is there a prefered range within which the L/D ratio for a vessel should fall into?

2. Instrument Nozzles, in particular the flange bolt hole orientation. How are the bolt holes for the nozzles normally orientated? Are the centreline bolt holes perpendicular to each other (with centreline passing thru the bolt holes centrelines). Is this the standard practise and does the code mention this? Otherwise how would the level gauge manufacturer know the position to orientate his level gauge mating flanges?

Thanks.

 

[JStephen]

#1- Not really. If there are no other restraints, fabricators will pick the most economical dimensions, which may vary from one to the next. Factors involved would include available plate lengths, head sizes, shop capacity, shipping restraints, etc.

 

[DavidCR]

For 1. on cylindrical tanks there are preferred L/D values that would affect a lot the required thickness when seismic load is an important issue, maybe for most presssure vessels, where the thickness requirements are different it would not be aplicable, but I mention the point just in case you are interested in.
For a tank filled with liquid the L/D or Height/D ratio must be around 0.5-0.6 for seismic zone 4 if one does want to have decent plate thicknes, you can read more on this on the tanks (AST) manual of Philip E. Myers.

 

[codeeng]

#2 You should always specify flange bolt holes to straddle centerlines (i.e. off centers). You instrument supplier should default to this.

 

[codeeng]

DavidCR
"L/D or Height/D ratio must be around 0.5-0.6 for seismic zone 4 if one does want to have decent plate thicknes"

I doubt any thickness would be effected within these parameters?

 

[codeeng]

.....That is vessels can go much taller than this without effecting thickness.

 

[JStephen]

"Pressure vessel" is a fairly generic term. If you can be more specific about what you're doing, we can get you better answers.

 

[Engineer6512]

#2 - don't assume any default... make sure to write in your specification what you are looking for.

Steamguy2

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