Arc Machines 307 - Manual (Page 116)

Arc Machines, Inc. Model 307 Orbital Tube Welder Training
Document No. 740096 Chapter 9. Page 12.
Rev. A
primary RPM is set to 1/2 the calculated RPM (based on 5 IPM) and the back-
ground RPM is set to the calculated RPM may be effective in increasing pene-
tration without reducing the time per weld as much as setting the primary RPM
to 0.0. STEP RPM may be based on 4 IPM instead of 5 IPM. Actual travel speed
is slower in STEP mode.
Size Considerations
Orbital fusion welds are practical on diameters from 1/8” to 7.0” and wall
thickness from about 0.010” to 0.154” wall with standard fusion welding
equipment. Orbital equipment with AVC (automatic voltage control) which
maintains a constant arc gap extends the range for autogenous welding to
schedule 10 pipe up to 10, 12, or 14 inches IPS. However, not all welding
techniques are applicable to all sizes. STEP rotation mode and mixed gas are
often used to increase penetration on heavier-walled pipe.
1/8” OD tubing can be orbitally welded either with single or multi-pass tech-
niques, with or without pulsation. At a travel speed of 5 IPM, the RPM would
be 12.7. At 7 IPM, the RPM would be 17.8 or 18 RPM which is approaching the
maximum RPM of the 9-250 and 9-500 weld heads which is 20 RPM and is out
of range of the other weld heads. It takes the right equipment and “know-how”
to properly cut and face tubing of this size for orbital welding without damag-
ing the tubing. Furthermore, inspection of the ID for penetration is virtually
impossible without destroying the weld. Thus frequent test coupons are rec-
ommended.
1/4” OD tubing is typically welded at 8 RPM for a single-pass weld with
pulsation which is a travel speed of 6.28 IPM. This is slightly faster than the
usual 5 IPM. Although some users have made successful welds using 5 IPM,
or 9 IPM, the 6.28 IPM has been widely used with consistent results using the
1 amp per 0.001” wall formula.
5 IPM is recommended as a travel speed for sizes from 3/8 inch to 3.5 inch
O.D. tube. Faster travel speeds are possible with very thin-walled materials.
5 IPM