CHANGE, FLUX CORED AND
WELD PROCESS EVOLUTION: The small diameter, < 1.6 mm gas shielded, flux cored wires
that offer so many practical benefits for all position welds were developed more than thirty years ago. During the last three decades, the evolution from the shielded metal arc welding (stick) process,
to the gas shielded flux cored process has for many pressure vessel shops,
pipe shops and contractors been both painful and slow. Today in 2013 it's still an uphill struggle to get managers and engineers
to buy into the cost effective flux core welding process and when this process is used, it's rarely optimized.
Weld process change never comes easy to pipe - vessel weld shops in which pipe welders are
entrenched and comfortable with the
traditional skiils as required by the SMAW
and GTAW process. In this enviroment weld process change
is also influenced by hands off managers or engineers who typically have minimal expertise on the allternative semi-automatice weld processes.
WELD FACT: As
both the SMAW and GTAW equipment provide a simple, single weld current control, a welder needs minimal weld process control expertise with
these two common weld processes.
Many weld shop confuse "weld skills" with weld process control expertise.
contrast to the SMAW process, the MIG equipment that's used for flux cored welding
allows a welder to produce different modes of MIG and flux cored weld transfer.
lack of weld process control expertise is also too common in the weld fabrication departments
that utilize the MIG and flux cored processes. In these weld shops, it's not uncommon to watch the weld personle "play
around" with their MIG weld controls.
IF THE MANAGEMENT AND ENGINEERS ARE NOT AWARE OF THE REQUIREMENTS FOR WELD PROCESS OPTIMIZATION, HOW WILL THE WELDERS - TECHNICIANS AND SUPERVISORS EVER GET THE TRAINING THEY NEED:
WELD SKILLS ARE A SMALL PART OF WELD OPTIMIZATION: As
many companies that use weld automation are aware, when using either
the flux cored or MIG process, it takes more than weld skills and playing with
weld controls to achieve consistent quality welds.
weld shops that have utilized the common wire welding processes and have focused
on the welder's skills rather than on the welders weld process expertise will
over time have paid extensive, unnecessary welding costs.
THE OIL SANDS PIPE WELD PROJECT:
1998, an egineering manager at Imperial Oil, Calgary. Alberta Canada, asked
if I would:
Evaluate the oil and natural gas field and shop pipeline welding practices
used by their contractors on the Cold Lake project Alberta, Canada.
Examine methods to reduce field pipeline construction welding costs on a natural
gas steam pipe project.
As the majority of their pipe welds were made with the costly SMAW process, Imperial Oil asked if I would come up with a weld process training program that would encourage the contractors and their union employess to embrace the more cost effective flux-cored-arc and MIG welding process for both the field and fabrication shop welds.
Provide the senior pipeline management, welders and weld supervision with the requirements necessary for flux cored pipe weld process optimization.
Note: The pipe
contractors had resisted the change to flux cored for many years. To attain across
the board acceptance of the flux cored process, we decided that the best strategy
would be to gather all the key weld personnel at a location in which both classroom
and hands on weld training could be provided. The Southern Alberta Institute of
Technology (SAIT) located in Calgary, Canada, kindly provided us with one of the
best equipped weld training facilities in North American.
THE TRAINING PROGRAM: For
the flux cored process introduction and weld process training, I developed an intensive
three-day training session. The weld process training required both classroom
and hands-on pipe welding for the pipe line contractor's key welding personnel.
The flux cored training covered the requirements to weld high strength, carbon steel pipe
diameters that varied from 100 to 600 mm (4 to 24 in) diameter. The training provided
the welders with the required flux cored, best practices, techniques and skills, but just as important
the training also placed great emphasis on ensuring the participants had the
flux cored weld process knowledge necessary to "set optimum weld parameters"
for any manual or automated, EXXT-1 consumable size and any pipe applications.
training program was very well received, and in less than 16 hours of welding pipes
and discussing the necessary weld process controls we had one hundred percent
acceptance from participants who had never successfully welded with flux cored.
After completing the training, I then followed up with visits to the companies
pipe shop to provide weld process support during the SMAW to flux cored transition.
Cost Savings and the Imperial Oil pipe welds:
goal of the SMAW to flux cored conversion was to improve the pipe weld quality and productivity when welding low alloy steam pipes. The common sixteen-inch (40-cm) diameter
pipe has a 1 in. (25-mm) thick wall, with a 60-degree bevel for the weld. The
steam pipe, CSA Grade 448 (X65), operates at 2,500 psi, at 650 F. The specified
minimum yield strength is 65,000 psi, with UTS at 80,000 psi.
HIGH QUALITY: The pipe
weld qualification was to ASME B31.3, with required weld tests performed to ASME
Section IX. One of the main differences from a traditional pipeline code is that
the bend test subjects the weld to a "20 percent Strain", compared to 12.5 percent
Strain for many pipeline qualification tests.
The steam pipe was typically weldedwith E8010G stick (SMAW) electrodes. The
stick process required the use of 350 F preheat to minimize hydrogen cracking.
In selecting a suitable flux cored consumable I tested many of the available all
position E71T-1 and E81T-1 flux cored wires. The flux cored wire I found most suitable
for this project was a product developed by Alloy Rods.
SELECTING THE OPTIMUM WELD CONSUSMABES:
E71T-1, Alloy Rod flux-cored electrode I selected had the best weld puddle control
especially in the critical and difficult overhead welding positions. The
E71T-1 wire was developed for use with straight CO2, however a the tensiles produced were marginal, I decided to try this
weld wire with an argon - 25% CO2 mix. The weld transfer produced was greatly improved and the mult-pass welds produced provided
a minimum of 90,000 psi tensile strength.
BENEFITS. BEVELS AND PRE-HEAT REDUCED: The
success of the flux-cored wires on this project eventually prompted a change from
the traditional 60 degree bevel to a compound bevel that dramatically reduced
the required amount of filler weld metal. The controlled low hydrogen content
of the flux-cored wires also allowed reduction of the 350 F preheat to 200 F.
These two changes provided dramatic cost reductions that are not included in this
Process, and Pipe Welding Considerations
many decades, pipe - vessel shops and pipelines made the majority of their welds
with SMAW electrodes or with the gas tungsten arc process. Although the SMAW electrodes,
arc characteristics and properties have greatly improved, these
electrode in contrast to gas shielded flux cored electrodes provide lower weld
fusion potential, lower weld deposition rates, lower weld deposition efficiency
and more propensity for hydrogen pick up. However the SMAW process has been successful
as the process has provided some unique weld attributes for specific pipe applications.
in an industry in which weld equipment electronic bells and whistles often receive more
consideration than an electrode's welding characteristics, the important attributes
of a weld process or consumable are often overlooked. When considering pipe welding
process alternatives, it's important to remember the primary features and benefits
of the successful SMAW process.
prime attributes of the SMAW process include:
The constant current welding equipment with the single weld control is simple
to operate and inexpensive to purchase. The equipment is typically durable and
simple to repair..
The SMAW electrodes provide a fast freeze weld slag which for all positions welds that can assist in the control
of the weld.
C. The SMAW process provides different weld polarities that can deal with weld equipment, weld fusion and arc blow issues.
D. In contrast
to the alternate semi-automatic weld processes, the SMAW weld process requires minimum "weld
The SMAW electrode manufacturers can formulate their electrode flux to meet difficult
chemistry and mechanical requirements.
The low weld deposition rates achieved with SMAW is actually beneficial for "manual"
pipe welds. The low weld deposition rate requires the welder to travel at a low
manageable weld travel rate. The slower the welder travels the more time is available
for the welder to direct the fast freeze weld into the pipe
Concerns With Pipe Welding Alternatives
used in pipe shops, MIG equipment, is rarely optimized, and when flux-cored products
were introduced by the local weld sales reps, the flux cored consumables were
rarely demonstrated in the approved manner. However the flux cored process, described
by one welder as a stick electrode on a 30 pound reel has a lot more in common
with the prime attributes of the SMAW process than any of the MIG processes.
With the flux cored and SMAW process similarities, its difficult to understand
the pipe industries reluctance to embrace flux cored, while at the same time they
seem to have an infatuation with the sophisticated, electronic pulsed MIG and
the Lincoln STT processes.
I believe while the traditional MIG, pulsed
and STT processes are a good tool for welding a root and mechanized welding, these
processes cannot out perform an all position flux cored wire used for manual applications.
MIG traditional short circuit mode is a practical weld choice for welding a pipe
root pass with a "rotating" pipe that has fixed controlled open root
dimensions. The traditional MIG short circuit, globular or low end spray modes
can all be used very successfully for vertical down root and hot pass welds made
"inside the pipe".
using narrow bevel pipe weld joints, and the pulsed MIG, globular or the STT weld
processes, the wise weld decision maker will remember that these processes at
best provide only minimum side wall weld fusion potential. For pipe companies
using these process the welding circumstances may require extraordinary, costly
weld inspection methods.
the flux cored process if applied correctly, a company should have no issues with
a narrow pipe bevel. However in order to use a narrow bevel and the automatic
MIG modes, the weld inspection may require shear wave ultrasonic examination.
This mode of inspection is necessary so the NDT equipment can size the flaw, and
determine if it is acceptable, based on crack, tip opening displacement, (CTOD)
and fracture mechanic equations. This will also require the regulator to accept
alternate inspection rules. Pipeline companies are becoming aware of costs incurred
in complex inspection criteria and also with the cost of the weld repair issues
that can result. When using weld processes that provide minimum side wall fusion
the necessary field machining of the pipe ends can also obviously cause issues
from the pipe roundness deviations. What is often ironic is when the pulsed MIG
or STT welds require weld repairs, the best process choice for the repairs would
typically be either the SMAW or flux cored process.
visit to any manufacturing
facility using MIG or flux-cored wire in North America would likely reveal the
When setting the two MIG or flux controls on traditional MIG equipment the welders
typically will end up "playing around with the controls."
Ask the engineer managing the process or the welder using the gas-shielded flux-cored
wire what the optimum wire feed and voltage range are for that wire. Then see
the blank gaze that will often follow.
Ask the welder or the engineer what the MIG, 0.035 in. (1 mm) diameter wire feed
rate is for the start point of spray transfer and the blank gaze returns.
the weld decision-maker can select from a wide variety of welding equipment and
welding consumables when producing pipe welds.
Traditional MIG equipment using with short circuit, globular or low current spray
transfer for vertical down root and hot pass welds.
The Lincoln Electric STT power source, (similar to a low pulsed setting) which
in contrast to short circuit provides a slight improvement in the weld fluidity
attained. Suited for the root passes.
Traditional short circuit, pulsed or STT with metal-cored wires.
Pulsed MIG with MIG wires used for vertical up-down welds.
A pulsed unit using ac/cc, using MIG or metal cored wires.
Traditional MIG spray with regular MIG or metal-cored wire for rotated pipe fill
position, gas shielded flux-cored wires for fill passes, typically made in the
overhead and vertical up positions.
All position gas shielded flux cored wires designed for vertical down welds
Gas tungsten arc or the plasma welding process.
10. Twin MIG or metal
The Miller RMD a short circuit mode in which for a given wire feed rate provides
12. The Fronius CMT process, another modified short circuit
appropriate weld process expertise, and a short training period, all the above
weld processes and consumables can be relatively simple to operate. The primary
challenge for many weld decision makers is to cut through the often sales biased
weld process and product information that can often influence a weld process decision.
testing short circuit on the pipe root.
Perspective on MIG and Flux Cored Weld Automation:
year robot sales in the USA increase dramatically, yet robot weld efficiency in
this country rarely exceeds sixty percent, and on many robot applications the
weld rework generated daily creates unnecessary manual intervention. With robots
or pipe weld automation we often find the same welding process issues that are
found in the manual welding shops. One of the biggest challenges any weld decision
maker has, is ensure that the new robots or automated welding equipment does not
inherent the bad weld practices found in the manual weld shops.
prime factor for poor automated weld quality or productivity performance is again
a "lack of weld process expertise
fully optimize either the mechanized or manual MIG or flux-cored wire processes,
weld decision-maker needs to:
Be aware of the weld process fundamentals.
Be knowledgeable of the electrode wire weld parameter ranges, and the parameter
relationship with the weld equipment controls.
Be aware of the primary feature benefits and disadvantages of each weld process
and consumable utilized.
Understand that the primary method for weld cost control comes from understanding
the wire feed and weld deposition relationship.
Understand the relationship between weld current, wire diameter and part thickness
technicians know that the majority of pipe weld defects that require weld rework
and additional costly weld radiographs occur typically in the root, and the first
hot or fill pass, and also at or at the weld starts and stop tie ins. Most manual
MIG and flux cored weld defects are greatly influenced by the welders using inappropriate
weld settings, poor weld practices and stick welding techniques.
automation allows control of both the weld speed and the weld weave and sophisticated
power sources and automated equipment enable weld data to be changed at any pipe
location, in the weld joint.. These are key elements to attaining consistent pipe
weld quality. Of course automation will also dramatically increase the potential
weld productivity attained.
are almost as many options to mechanize field pipe welds as there are welding
processes. We could weld the field pipe line with my Robo Rig with two robots mounted on
a tractor that straddles the pipe. We could use simple Bug-O carriage
equipment or purchase the more durable and sophisticated automated pipe line welding
1998 ED SET THIS ABB ROBOT TO FLUX CORED WELD A
48 INCH PIPE IN THE 5G POSITION.
THE WELDS WERE PERFECT AND THE SLAG FELL AS THE WELDS WERE MADE.
the welders were comfortable with the manual flux cored process the engineer responsible
at Imperial Oil asked if I would now move them into automated pipe welding On
the Canadian, steam pipe line project, in contrast to the manual stick welders,
two mechanized weld carriages using flux-cored wires could provide:
A reduction in weld start and stops from more than 100 to 12
Consistent mechanized weaves that optimize side wall fusion on both sides of the
weld travel speeds that ensure consistent weld fusion.
Flexibility. With the hands off mechanized units and a portable weld parameter
control, the operator has the ability to change the weld parameters if necessary
The mechanized unit allows higher wire feed rates which will increase the weld
In contrast to the inconsistent manual welders, a mechanized unit will have far
superior control of the weave configurations. This is an important consideration
with flux cored as larger weld weaves can reduce the number of weld passes. For
example, the manual welders do three passes for the SMAW pipe cap pass. A mechanized
unit with flux cored will do the cap in one or two passes at a third of the time.
weld managers should be aware of the benefits derived by keeping their welding
operations simple, keeping unnecessary bells and whistles off the mechanized welding
equipment and use a common sense approach to the pipe welding process and procedures
an industry is ready to spend thousands of dollars on welding equipment and only
pennies on weld process training, there will be dramatic weld cost repercussions.
The resolution to weld process control
is not found on the weld shop floor or among the welders at a pipe line, it's
found in the head of the project manager or engineer responsible. If the weld
decision makers don't have the weld process expertise or data they need, they
should try two old fashioned solutions, "hire it or read a book".
are Benefits of Shielded Metal Arc Electrodes For Pipe Welding:
you evaluate the benefits of available welding process technology and disregard
the sometimes biased sales advice then you can conclude the following for field
pipe line welding.
variables can effect the field pipe root dimensions. If the skilled labor force
is available, the vertical down SMAW process has always been and still is today
the practical choice for many root pass welds performed both in the field and
in fabrication pipe shops. As the SMAW root pass is typically not thick enough
to support the weld penetration potential of the higher energy flux-cored weld.
It is logical when SMA welding to also provide one or two hot passes with the
SMAW process used for the pipe root is still the best choice if the pipe root
gap or pipe dimensions vary.
thin wall pipe, spool applications or where the pipe diameter is less than 15
cm, its often more logical if the skilled labor is available to use the SMAW process
or even the GTAW process rather than utilize the pulsed or STT process.
Line Welds and Gas Shielded Flux Cored Wires:
small diameter, gas shielded, all position, flux-cored electrodes can provide
many unique welding benefits when used with traditional constant voltage MIG equipment,
or with CC generators that provide a CV adapter. Similar to the traditional MIG
process, the flux-cored process requires only two weld parameter settings, a volt
setting and a variable wire feed control that regulates the welding current.
flux-cored welding process, while simple to operate, has inherited "people
process issues" that are international in scope. I have been in more than
1,000 manufacturing facilities in 12 different countries. Of those using flux-cored
wires, more than 80 percent were using:
The wrong electrode wire diameter.
(Note, for managers and supervisors, bigger
is rarely better)
The wrong electrode wire type. E71T-1 is not the best wire for many horizontal
The wrong gas, why use CO2 if the wire runs better and smoke is reduced with an
Inappropriate welding parameters.
Inappropriate wire stick out and the use of unsuitable stick weld techniques.
I reemphasize the weld process issues to reflect the universal lack of weld process
focus that is prevalent not only in the pipe industry but in most manufacturing
With optimum weld data and consumables the slag
falls of by itself.
Cored Weld Deposition Rates.
gas-shielded flux-cored wires, specifically those developed in North America by
Alloy Rods and later on Tri Mark, have had the greatest impact on simplifying
all position welds on carbon steels, alloy, and stainless pipe applications. Due
to the ease of use and their cost effectiveness, flux-cored wires have painfully
wormed their way into two other entrenched industries, ship yards and heavy plate
all position flux-cored electrode wires have today evolved into consumables that
in contrast to SMAW electrodes can conservatively triple the daily weld deposition
rates for vertical up or overhead welds.
typical weld deposition rate for a vertical up, pipe fill pass weld with a stick
electrode would be 2 to 3 lb./hr, (0.9 to 1.3 kg/hr). In contrast for the same
welds a conservative and "average" weld deposition rate of 8 lb./hr
(3.6 kg/hr) is attainable with either the 0.045 and 0.052 in. (1.2 to 1.4 mm)
flux-cored wires. Specific all position flux-cored consumables can produce 9 to
12 lb./hr (4.5 kg/hr) for vertical up welds on components thicker than 8 mm.
this pipe project I selected an Alloy Rod E71T-1 0.052 in. (1.4 mm) diameter flux-core
wire for all the fill passes and the cap pass. I selected the wire based on its
low weld current requirements and on its welding capability in the overhead positions.
As the welders had minimal flux cored experience the flux-cored wire feed selected
(current) was conservative and provided a weld deposition rate of a little more
than 6 lb./hr (2.7 kg/hr). The weld parameters I selected enabled the welders
to weld the multi-weld pass application with only one wire feed setting. One weld
voltage adjustment was required for the pipe cap pass.
The Flux Cored Weld Process Influence on Weld Layers and Arc Starts
two manual pipe welders using the E8010 SMAW electrodes, welded 110 arc starts
in 13 fill passes. The low weld deposition rate produced short weld lengths and
layers of welds with little depth. In contrast the higher weld deposition flux-cored
wires reduced the number of weld layers by 50 percent.
welding the fill passes using a mechanized pipe welding system or a simple carriage
and track system that provides two carriages and torches. The 0.052 in. diameter
flux-cored wires, could starting at 6 o'clock and traveling to 12 o'clock, complete
half the diameter of a 16 in. pipe in a single weld pass. Each weld gun would
weld a total of 6 flux-cored fill passes . This could result for this pipe project
in a total 12 arc starts (six each side) for the fill passes in contrast to the
110 arc starts required with the two manual welders and SMAW electrodes.
utilizing flux-cored wires instead of SMAW electrodes, the pipe contractor could
reduce the arc starts and lack of weld fusion potential at the arc starts by almost
90 percent. When using flux cored instead of pulsed MIG or STT on automated pipe
projects less fill passes and less tie-ins will be required. The time saved will
allow the operator to clean the slag between weld passes.
of Flux Cored Weld Current Density
traditional 3.2, 4, and 4.8 mm SMAW electrodes used for pipe welds use a weld
current range of 100 to 180 amps. In contrast the all position, flux-cored wires
that are optimum for pipe welds are 0.045 or 0.052 in. (1.2 or 1.4 mm) diameter.
These smaller wire diameters typically use a weld current range of 160 to 220
A. The flux-cored weld current range with the small electrode diameter creates
a higher weld current density that results in greater arc energy in the weld pool
than that produced by SMAW electrodes.
high weld energy and resulting higher weld fluidity of the flux cored weld provides
flux cored consumables with their greatest asset for pipe welds, the potential
for superior side wall penetration.
flux-cored wire is unique in contrast to the MIG processes in that it offers high
current density with a fast freeze weld slag. The weld slag generated with the
SMAW E8010G electrode is sometimes
tenacious in the way it clings to a weld.
In contrast a well manufactured flux-cored wire will produce a weld slag that
should peel of while welding.
Cored Features and Benefits.
welding offers a number of features and benefits in contrast to the SMAW process.
Flux cored provides higher weld deposition rates. For this pipe project 75 percent
less time was required to complete the 16 in. pipe joint.
Flux cored requires less arc start and stops. On this pipe project, there was
a 80-90 percent less potential for start stop weld defects.
Flux cored provides greater arc energy with improved weld fluidity. This dramatically
reduces the potential for side wall and arc-start weld fusion defects. With flux
cored, today the normal, manual weld reject rate at the field pipe site is 0 to
1 percent. In contrast with SMAW electrodes the reject rate was 3%.
Flux cored produces smooth weld tie-ins, and reduces weld undercut potential and
the need subsequent grinding.
cored produces thicker weld layers. Less filler weld passes reduces the weld tie-ins
and the potential for arc-start fusion defects.
Flux cored produces longer weld lengths, reducing weld tie-ins and improving productivity.
Flux cored weld slag is easy to remove reducing the potential for weld slag entrapment
Flux cored provides lower weld hydrogen content and lower potential to absorb
hydrogen, this minimizes potential for hydrogen cracking issues,
Flux cored provides faster weld travel speeds which can result in lower weld heat
input. A benefit for quenched and tempered pipe.
Flux cored requires less welder skill requirements than both the SMAW and MIG
processes. With this process its easier to train welders and you can expect fewer
defects from welders of all skill levels.
This pipe project when using SMAW required preheat of 350 F. In the cold climate
of Northern Canada its difficult and time consuming to attain this preheat temperature
on thick wall pipe. The lower hydrogen potential of the FCAW electrodes reduced
the weld preheat requirement to 200 F.
FCAW fill pass features and benefits in contrast to the MIG processes.
With flux cored we can use one weld procedure, a narrow wire feed / voltage range,
it can be simpler to operate.
Flux cored provides a slag that molds the metal requiring fewer welder skills
and slowing the cooling of the weld which reduces weld porosity potential.
Flux cored provides higher weld energy and a more penetrating weld than either
pulsed, STT or globular.
4. Flux cored weld equipment costs much less
than pulsed or STT equipment.
5. Flux cored equipment is more durable
and easier to repair than electronic power sources.
Flux cored is less sensitive to contaminates or arc blow.
Cold Lake Pipe Line Welding Costs:
welding the electrode costs are typically only a small portion of the total welding
costs, it is interesting to compare consumable costs of the SMAW process to flux-cored-arc
pipe line contractor provided the following SMAW electrode data. The pipe weld
crew of 10 welders and 10 helpers welded 16 pipe joints each day on the 16 in.
(40 cm) diameter pipe. The weld crew comprised of a "tack-root crew",
two welders and two helpers, who welded the root, they then welded one or two
hot passes. The pipe fill passes were made with E8010-G electrodes. Four weld
crews, including two pipe welders, one either side of the pipe plus two helpers,
welded the fill passes. Each fill welder would weld 13 fill passes and a cap pass.
Each four-man crew would weld 4 pipe joints per day.
Each E8018G 3/16 (4.8 mm) electrode used on the 16 in. pipe averaged a weld length
of 5 to 6 in. (12.5 - 15 cm). For each of the 13 fill passes, each welder welded
approximately 24 in. (60 cm) of the 48 in. (120 cm) pipe circumference. Four electrodes
per pass were required. Each welder used 50 to 55 electrodes to complete the pipe
fill passes per pipe joint required a total of 110 SMAW electrodes One of the
most common weld defects found in the SMAW pipe welds is lack of weld fusion that
occurs at the arc starts. Given the field conditions, the high quality standards
and high number of arc starts, it is an attribute to the stick welders skills
that their weld repair rate was less than 3 percent.
Electrode Costs: There are approximately eight 3/16 x 14 in. (4.8 mm - 350 mm)
SMAW electrodes per pound. The contractor paid $1.64/lb. (Canadian dollar equals
65 cents of the US dollar) for the 3/16, E8010 electrodes. The 110 electrodes
used for the fill passes required approximately 13-14 lbs of electrodes at $1.64
lb. = $23 for the filler metal fill passes, which contained approximately 4 lb.
of actual weld filler metal.
Weld Deposition Efficiency:
If you buy a pound of SMAW electrodes,
how much electrode ends up as weld in the pipe joint? The electrode efficiency
at this pipe project averaged 35 - 40 percent. In contrast, the flux-cored wires
provided a weld deposition efficiency of 80 - 85 percent.
the thirteen fill passes on the 16 in. pipe weld it took 13-14 lb of SMAW electrodes
- 14 lb. x $1.64 = $23). Fourteen pounds of fill pass electrodes for a weld joint
that required approximately 4 lb. of actual weld metal. In contrast with the flux
cored process, for each pipe joint we had to purchase 5 lb. of flux-cored filler
at $1.70 lb. x 5 = $8.50 in versus the $23 required for the stick electrodes.
estimate the annual electrode costs: In a year with 240 working days per year,
the total weld joints for this pipe project which has gone on for many years could
be 3,840. The annual SMAW electrode costs $23 x 3,840 pipe joints = $88,320
for SMAW electrodes. The annual flux cored electrode cost $8.50 x 3,840 pipe joints
MIG or flux cored we have to add in weld gas costs. The all position flux-cored
electrode will use an 75 Ar-25 CO2 gas mix. A typical North American gas cylinder
costs $40. The argon mix cylinder will contain approximately 300 cuft.. (13 cents
per cubic/ft.) The pipe welds will use an average flow rate 35 ft cubic feet /
hr. The fill and cap pass require an arc on time of approximately 45 minutes,
using approximately 27 cubic feet of gas, (27 x 0.13 cents = $3.50 gas cost/joint).
Adding the gas cost to the electrode cost of $8.50 per joint = $12 per total
consumable cost per flux cored joint versus $23 for the SMAW electrodes per joint
cylinder of gas will last for 11 to 12 pipe joints. For this project of 16 pipe
joints per day, 2 x $40 cylinders per day times 240 days = $19,200 per year. Add
cylinder rent and the gas costs should be approximately $22,000. The annual gas
cost when added to the annual flux-cored wire cost of $32,640 would total a weld
consumable cost of $54,640 in contrast to $88,320 for SMAW. This provides a yearly
weld consumable saving of approximately $34,000.
more costly flux cored wires and shielding gas reduced the pipe line weld consumable
costs by approximately 40 percent.
Labor Costs and Real Welding Cost Savings.
complete the fill passes in this pipe joint, with two welders and two carriages
with 0.052 in. (1.4 mm) diameter flux-cored wires, required six weld passes for
each joint side. For the six weld passes an average continuous weld travel rate
of 8 in/min. (20 cm/min.) would be selected. To weld each of the 6 fill passes
(24 in. of the pipe circumference) would take approximately 3 minutes x 6 passes
= 18 minutes x 2 carriages = 36 minutes of "actual arc-on-time". With
a weld deposition rate of 6 lb./hr (2.7 kg/hr) the 36 minutes delivers 3.6 lb./hr
(1.6 kg/hr) of actual weld metal deposited.
the pipe site, a total crew of 37 completed sixteen pipe joints each day. This
natural gas and oil producing site has many of miles of pipe that are run each
year. The fill and cap crew used 8 welders and 8 helpers, 16 workers to complete
the fill passes on the pipe joints. With the reduced preheat requirement, significantly
higher weld deposition rates and almost complete elimination of grinding between
passes, 3 welder and helpers, or 6 workers now complete the same amount of work
that 16 worker produced.
reader can insert all types of overhead charges for weld cost reductions. However
as an example: If the total overhead cost per person at the pipe site averaged
$40/hr, then the savings with the 10 men reduction would equal to $400/hr. Assuming
roughly 2,000 hrs./year employment time, and the annual labor savings would be
$800,000. In addition to the $800,000 cost reduction there are other substantial
cost savings due to "softer" benefits:
weld repair costs.
to maintain production schedules if welders are in short supply.
Depending on metallurgy requirements, there is a potential to eliminate or greatly
reduce the required preheat..
reduced labor, weld repair cost reductions, the later reduction incurred from
the narrow vee-prep which greatly decreased the amount of weld required and the
lower net consumables cost, it is not unrealistic to expect a conservative weld
cost savings to exceed $1,000,000 per-year on this ongoing
Conclusion on Cost Effective Weld Choices
mentioned there are numerous ways to approach a pipe line weld project or welding
a pipe spool in a fabrication shop. When comparing a pipe weld process, the weld
reality is this. If you worked in a fabrication shop and your task was to produce
a simple vertical up, and over head 1/4 (6 mm) fillet weld on 3/8 (10 mm) plate,
and you had five welding choices --
3. All position, gas shielded flux cored wires.
4. The stick process.
5. Traditional MIG.
would be so many instant weld benefits attained from the flux-cored wires that
it's unlikely anyone would give the other processes the slightest consideration.
This is the simple reason the flux-cored process is the prime weld process choice
of ship yards and fabrication shops that work with thick plate. The information
you attain at this site may not be what you hear from weld equipment manufacturers,
(they sell equipment). From this weld application engineer's perspective, any
pipe line that evaluates a pipe welding process should ensure its:
Simple to operate.
B. Provides superior weld fusion.
C. Requires less
D. Provides the desired mechanical properties.
the highest weld deposition rate potential.
years ago, in contrast to the traditional MIG weld transfer modes, that superior
weld process was a flux cored wire using a low cost durable CV power source or
a generator. In the year 2001 and today in 2008 when you stack up all the sophisticated,
costly MIG equipment its still difficult to compete with a flux cored consumable.
|In 1985.. Ed
made this 310 stainless 5G pipe weld using MIG 310 root
and filler welds with
one set of welding parameters. All the welds were made vertical up.