Page 227 - Handbook of Structural Steel Connection Design and Details

Welded Joint Design and Production

212 Chapter Three

bulletin boards have listings of typical WPSs used in the organization.
Some suggest that WPSs should be posted near the point where weld-
ing is being performed. Regardless of the method used, WPSs must be
available to those authorized to use them.
It is in the contractor’s best interest to ensure that efficient commu-
nication is maintained with all parties involved. Not only can quality
be compromised when WPSs are not available, but productivity can
suffer as well. Regarding quality, the limits of suitable operation of the
particular welding process and electrode for the steel, joint design, and
position of welding must be understood. It is obvious that the particu-
lar electrode employed must be operated on the proper polarity, proper
shielding gases must be used, and amperage levels must be appropri-
ate for the diameter of electrode and for the thickness of material on
which welding is performed. Other issues are not necessarily so obvi-
ously apparent. The required preheat for a particular application is a
function of the grade(s) of steel involved, the thickness(es) of material,
and the type of electrode employed (whether low hydrogen or non-low
hydrogen). The required preheat level can be communicated by means
of the written WPS.
Lack of conformance with the parameters outlined in the WPS may
result in the deposition of a weld that does not meet the quality
requirements imposed by the code or the job specifications. When an
unacceptable weld is made, the corrective measures to be taken may
necessitate weld removal and replacement, an activity that routinely
increases the cost of that particular weld tenfold. Avoiding these types
of unnecessary activities by clear communication has obvious ramifi-
cations in terms of quality and economics.
There are other economic issues to be considered as well. In a most
general way, the cost of welding is inversely proportional to the deposi-
tion rate. The deposition rate, in turn, is directly tied to the wire-feed
speed of the semiautomatic welding processes. If it is acceptable, for
example, to make a given weld with a wire-feed speed of 200 in/min,
then a weld made at 160 in/min (which may meet all the quality
requirements) would cost approximately 25% more than the weld
made with the optimum procedure. Conformance with WPS values
can help ensure that construction is performed at rates that are con-
ducive to the required weld quality and are economical as well. Some
wire feeders have the ability to preset welding parameters, coupled
with the digital LED display or analog meters that indicate opera-
tional parameters, which can assist in maintaining and monitoring
WPS parameters.
The code imposes minimum requirements for a given project.
Additional requirements may be imposed by contract specifications.
The same would hold true regarding WPS values. Compliance with

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