Drawing Scales

Hi I am new to piping and will be carrying out the drawing of layouts etc using autocad and am a bit baffled by the drawing scales

I understand for examle a 1:250 scale would show every 250mm in realality shown as 1mm on the drawing.

But how does this work with different size drawing sheets, Ao, A1, A2, A3 etc

Do I simply draw the layout 1:1 and then scale it down to fit on the drawing sheet I am using?

I was looking at a drawing today that at full size print (A0) the scale was 1:250, but in Aucad modelspace it was 1:1 and a viewport was not used, and this has confused me extremely

Any advice would be greatly appreciated

Thanks

Pab

Thankyou very much Anton,

That has been of great help to me,

Pab

Me too agree with Anton.....!

Anton's solution would be the most common in EPC companies. Try to avoid placing the border in model space in a 3D model as this will show in model review software and becomes cumbersome when you have to turn layers off not to show the border. Text also becomes an issue in model space as the text must be scaled to show correctly as per scale. In Paper space all text and symbology can then be placed at 1:1.
Also the viewport can change scale if need be although once the annotation is placed that requires more rework and should be avoided. If you use standard scales like 1:50 & 1:100 then there shouldn't be a problem.

Hello guys,

While working with the viewport method it is okay till there are no revisions in the scale however, it happens sometimes that we need to change the scale as per the later modifications / comments etc. & then the real problems are faced in viewport method.
In viewport method even though we can change the scale if it is needed but once the annotation (dimensions, texts, tags etc) are placed that calls for lots of rework/efforts to make it suit the new scale.
So it is observed that in most of the cases viewport method is avoided by the designers.

Normally, designers would like to draw the layout in Model space at 1:1 scale (as is) & then the border of A0/A1/other etc. is attached at 1:1 & then the border is scaled to suit the drawing.
That means, for a 1:250 drawing, the drawing is 1:1 but the border is scaled up by a factor of 250. When printed to A0/A1/other, this will achieve a 1:250 drawing.
Most of the times it works & accepted allover the world (as far as I seen, even the drawings received from our overseas counterparts are following the same procedure most of the times Ex-Netherlands, Houston, KL, Oman)

Can few of us on pipingdesigners.com can shed some light over this situation? After all we want to the things in right way (not the accepted way)