Page 246 - Handbook of Structural Steel Connection Design and Details

Welded Joint Design and Production

Welded Joint Design and Production 231

is used which is defined as the arc-on time divided by the total time
associated with welding activities. For SMAW, replacement of elec-
trodes takes place approximately every minute because of the finite
length of the electrodes used. The following operating factors are typi-
cally used for the various processes and method of application:

Method Operating factor, %
Manual SMAW 30
Semiautomatic 40
Mechanized 50

Operating factors for any given process can vary widely, depending
on what a welder is required to do. In shop situations, a welder may
receive tacked assemblies and be required only to weld and clean
them. For field erection, the welder may “hang iron,” fit, tack, bolt,
clean the joint, reposition scaffolding, and perform other activities in
addition to welding. Obviously, operating factors will be significantly
reduced under these conditions.
The following examples are the actual procedures used by a field erec-
tor. The labor and overhead costs do not necessarily represent actual
practice. The operating factors are unrealistically high for a field erec-
tion site, but have been used to enable comparison of the relative cost of
filler metals versus the labor required to deposit the weld metal, as well
as the difference in cost for different processes. Once the cost per
deposited pound is known, it is relatively simple to determine the quan-
tity of weld metal required for a given project, and multiply it by the
cost per weight to determine the cost of welding on the project.

Process SMAW FCAW
Electrode classification E7018 E70TG-K2
Electrode diameter, in 3 ⁄ 16 7 ⁄ 64
Amperage 225 430
Voltage NA 27
Electrode efficiency, % 60 80
Electrode cost, $/lb 1.23 2.27
Operating factor, % 30 40
Deposition rate, lb/h 5.5 14.5
Labor and overhead rate, $/h 50 50

For SMAW:
$1.23 $50.00
Cost per weight $2.05 $30.30 $32.35/lb
60% (5.5)(30%)
For FCAW:
$2.27 $50.00
Cost per weight $11.46 $8.62 $11.46/lb
80% (14.5)(40%)

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