Distance between welds 1

mazxx;
For piping, there is no recommended minimum distance between welds. Using good design practice I would offer this for your consideration regarding minimum distance between butt welds; 2*D for piping and 3*D for tubing. The rationale for the above recommendations is to avoid the effects of residual stress and the combined effects of the weld heat affected zones on each weld joint if they were adjacent to one another.

The spacing should be based of pipe wall thickness (t) not diameter.

To say the welds on say a 900mm pipe should 1800m part is a bit much.

In other forums I have see the spacing as 2t to 4t.