on the datum 1

[s1111]

Hello,
I noticed that when modeling compress the set datum offset, accounts for straight flange length. Could you thorw more light on the functioning of the datum.

Thanks in advacen for your comments.

s1111

 

[waskillywabbit]

The datum is a reference point for measurements. Typically we set ours at the tangent line of a head.

Brian

 

[TomBarsh]

You can find definitions of "datum" in a local dictionary or "online" on internet, such as:

{Datum line} (Surv.), the horizontal or base line, from which the heights of points are reckoned or measured, as in the plan of a railway, etc.


Thus the "datum" is simply a line used for reference, from which other locations are measured.

The "natural" datum in COMPRESS is either the "top weld seam" or the "bottom weld seam", as selected by the user on the Set Datum Line dialog (select Action menu, select Set Datum command).

Thus if you select "bottom weld seam", and design a vessel with top and bottom heads, a few cylindrical shells, and a support skirt, the datum line is taken to be at the weld seam of the bottom head to the adjacent shell. Nozzles, platforms, and other attachments may be referenced from this datum (reference) elevation.

Some users might prefer to work with datum (reference) line existing at the bottom tangent line. In this case set the "offset from datum seam" on the Set Datum Line dialog to the length of the head straight flange. You must also specify it as a negative value because the tangent line is below the "bottom shell seam".

Other users might prefer to work with the datum set to the bottom of the skirt base ring. Follow the same procedure to set the datum line.

Sometimes users need to specify the datum to some other location that may relate to "plant elevation", or maybe even to sea level. In this case the datum might be set to point that almost seems to be arbitrary on the vessel (eg: 33.1847" above bottom weld seam).

There is nothing magical about working from the tangent line. But it is convenient.

Tom Barsh
Codeware Technical Support

 

[s1111]

Thanks Tom for your valuable comments.

Regards,
s1111

 

[057BME529]

Dear guys

How would I add the nozzel that is tangent to the shell and has 90 degrees orientation? I did it just by keeping CL to CL distance + outer radius of nozzel equal to inner diameter of the shell but the nozzel is inside the shell which i don't want. Any suggestion will be appreciated. Thanks