What is "Industry Standard" for locating nozzles? 1

[EfficientPuppy]

There is some discussion in the office on what is the "right way" to locate a nozzle in terms of degrees on the the circumference. What we have found so far is in API 650 starting that north should be 0 degrees and north should be upwards per in L3.2.3, but there doesn't seem to be any mention that we can find that says which direction is positive from there, Counter Clock-wise or Clock-wise. This is trivial thing surely, but I was curious if anyone can point to something in any spec that shows some sort of standard. If not I guess I am curious, what is the standard that you use?

 

[RVAmeche]

I've never seen anything resembling a standard and every vendor will do it slightly differently. As long as the information is clearly conveyed it doesn't really matter.

In my experience it's very normal to provide the vendor a plan view showing angles (and radius from CL if on head), an elevation view or two for elevations, and an overall table of nozzle details.

 

[JStephen]

Most commonly, I would expect north to be zero degrees, east is 90, etc. But that varies and needs to be confirmed in each case.
Another variation is whether north is true north or plan north or what.
Pet peeve: I've dealt with some consultants that seem to just spin-the-spinner as to how a site plan is oriented on the page, just some random angle that seemingly doesn't line up with anything on the site is selected to point to the top of the page.

 

[Andrew ONeill]

It's designer choice.... but having being in operating plants for a long time, the most "useful" version is to define 0 Deg as the manway door / maintenance entrance and work clockwise from that, when looking down from above. (when doing tank inspections, very annoying to have to find plant north or true north when sitting inside a metal circle). This might not be useful for construction, but it is the go-to for doing maintenance inspections. Bonus points if all nozzles are numbered sequentially using the same system.


Regardless of the above I would always suggest have a reference / offset on the drawings to show the offset to "Plant North".

Andrew O'Neill
Specialist Mechanical Engineer
Australia

 

[IFRs]

In my experience, there are usually true north (sometimes magnetic north), plant north and drawing north (many times unique for each tank).
Nozzles are numbered going CW or CCW with no standard there, best to be consistent for the facility.
Degrees may be useless since on a 120 foot, one degree is more than a foot and degrees are only easily measured from the inside of the tank.
You are better off locating nozzles feet and inches [or mm] from an easily measured angle.