nozzle orientation and vessel centerlines 2

[lostsailor]

Greetings all,
When looking at a plan view (from the top) of a head with multiple nozzles and the flange bolt circles are to straddle
the normal vessel centerlines should the bolt circles straddle
the radial line or be oriented the same way a nozzle in the center of the head would be, straddling the 0 degree centerline. This question recently came up and a consensus hasn't been achieved and I can't find a definition anywhere.
Regards,
RLS

 

[JStephen]

Our convention on field erected tanks has been that they straddle radial centerlines of the tank.

If we know for some reason that attached piping is all aligned with tank north-south or east-west centerlines, then we'll switch and align bolt patterns with those centerlines.

 

[jte]

lost-

Please, please, please orient the nozzle's bolt holes along the same lines a nozzle in the center of the head would be (usually straddling plant North/South). I couldn't imagine the mess (well, actually, I could) with trying to fit up piping from one vessel to another and the pipe flanges have to straddle a line 27° off plant North on one end and a line 43° off plant north at the other end. I've never seen a plant, and would hope to never work in one, which doesn't align all of its flanges which are in the horizontal plane along the same global lines. This is a very basic example of applying the KISS principle.

jt

 

[codeeng]

Agree with jte. Bolt holes should ALWAYS straddle N/S cenerlines regardless of nozzle location.

 

[jlcochran1]

I agree, nozzles should straddle major vessel C/L's vs. radial. We have been manufacturing for over a century and have drawings back 40 years. This has been standard industry practice for decades. Most larger companies will have specifications clearly stating this.

Occasionally we will get a customer insisting on straddling radial centerlines. This creates confusion in the shop and field. The use of lap joint stub ends makes this a moot point though and is a shop preference whenever practical.

 

[MJCronin]

lost...

Try this link....

SUNOCO (and others) have had to develop a sketch or standard to demonstrate exactly what they mean

http://www.sunecp.com/sundocs/es/sketches/s0600/s6-10r0.pdf

MJC

 

[Shmulik]

May you guys add a short explanation: bolt holes straddle main CLs is well known and recommended good practice. Is there a mechanical reason for it (except of external piping installation)?

 

[codeeng]

Shmulik
The reason probably stems from the fact that piping is made-up from iso's where its convenient to callout "bolt holes to straddle piping centerlines". Vessels on the other hand are made-up from plan and elevation drawings where its easier to callout any special bolt hole off-set. In any case you can't argue with a Piper when it comes to orientations.