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WELDING ECONOMICS
The one issue not yet discussed is that of economics. Many things
affect the cost of welding including material costs, equipment cost,
labor rates and a host of others outside the scope of this paper.
For purposes of comparison time to complete a welded joint will
be used for a relative indicator of cost. The basic assumption is
that if equipment costs and labor rates are similar, the time to
complete a weld joint will be indicative of cost, less time translating
into lower costs and higher productivity. All comparisons will be
done using the typical joint detail used above to simplify the results.
In reality compound preparations may reduce the total time on heavier
wall pipe. Welding comparisons will use .750 in (19 mm) wall, 48
in (1219 mm) diameter pipe.
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TABLE 5. Typical Procedures
All Progression is down hill, 5G Position
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Electrode Type
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Current (Amp)
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Travel (In/Min)
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ROOT PASS
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5/32 EXX10
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135DC+
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11
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.068E71T-13H8
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190DC-
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7.5
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HOT PASS
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5/32 EXX10
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170DC+
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15
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5/64 E71T-8-K6
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245DC-
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15
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FILL AND CAP
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3/16 EXX10
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200-240DC+
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AS NEEDED
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5/64 E71T-8-K6
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300DC-
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AS NEEDED
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TABLE 6. Welding Times
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PROCESS ROOT
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PASS TIME (min)
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TOTAL TIME (min)
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ALL EXX10
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13.7
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241
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EXX10 ROOT, FCAW-S
FILL AND CAP
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13.7
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184
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ALL FCAW-S
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20.2
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164
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These times represent man-minutes of welding.
The joint done with all self shielded flux cored arc welding has
the lowest total time, but the combination of shielded metal arc
welding with self shielded flux cored arc welding will result in
the greatest amount of pipe laid on a given day because of the time
savings in the root pass. Tthis combination will result in the best
overall compromise of reduced total time and maximum pipe laid in
a given period of time.
CONCLUSIONS
As can be seen, shielded metal arc welding and self shielded flux
cored arc welding present cost effective ways to produce quality
welds under field conditions. Also, the best solution to field welding
of cross country pipelines is often is to use a combination of welding
processes.
REFERENCES
Welding Handbook, 8th Edition, (1991) American Welding Society,
Miami
The Procedure Handbook of Arc Welding, 13th Edition, (1994),
Lincoln Electric Company, Cleveland
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