SMAW - Single, Multiple Tandem, & Multiple Parallel Arcs

[appot]

I have a weld procedure in front of me for a CJP field weld of a beam flange.

The procedure is approved for single arc welding only. I am a little bit confused by what a tandem arc is.

Two welders with seperate power sources. Welder A welds the top flange while Welder B welds the bottom flange simultaneously.
Is this a tandem arc, or is the two single arcs?

If the above example is single, then what is tandem and parallel?

Thank you

 

[metengr]

Tandem arc welding is described below

http://www.thefabricator.com/articl...-the-tandem-welding-process-to-your-advantage

Parallel arc welding is done with multiple separate arcs connected to the same power source.

Two welders with separate power sources. Welder A welds the top flange while Welder B welds the bottom flange simultaneously.
Is this a tandem arc, or is the two single arcs?

Two separate welders with separate power sources.