TIP TIG Welding is always better quality than TIG and 100 to 500% faster with superior quality than TIG - MIG - FCAW.

1998" Ed's one million dollar pipe cost reduction for Imperial Oil Alberta.

CHANGE, FLUX CORED AND THE SLOW 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.

Note: Many weld shop confuse "weld skills" with weld process control expertise.







In 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. The 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:

During 1998, an egineering manager at Imperial Oil, Calgary. Alberta Canada, asked if I would:

A. Evaluate the oil and natural gas field and shop pipeline welding practices used by their contractors on the Cold Lake project Alberta, Canada.

B. Examine methods to reduce field pipeline construction welding costs on a natural gas steam pipe project.

C. 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.

D. 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.

The 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.

 

Weld Cost Savings and the Imperial Oil pipe welds:

The 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:

The 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 report.

Management, Process, and Pipe Welding Considerations

For 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.

Today 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.

The prime attributes of the SMAW process include:

A. 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..

B. 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 process expertise."

E. The SMAW electrode manufacturers can formulate their electrode flux to meet difficult chemistry and mechanical requirements.

F. 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 bevel.

Concerns With Pipe Welding Alternatives

When 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.

The 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".

When 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.

With 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.

A visit to any manufacturing facility using MIG or flux-cored wire in North America would likely reveal the following:

A. When setting the two MIG or flux controls on traditional MIG equipment the welders typically will end up "playing around with the controls."

B. 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.

C. 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.

Today the weld decision-maker can select from a wide variety of welding equipment and welding consumables when producing pipe welds.

1. Traditional MIG equipment using with short circuit, globular or low current spray transfer for vertical down root and hot pass welds.

2. 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.

3. Traditional short circuit, pulsed or STT with metal-cored wires.

4. Pulsed MIG with MIG wires used for vertical up-down welds.

5. A pulsed unit using ac/cc, using MIG or metal cored wires.

6. Traditional MIG spray with regular MIG or metal-cored wire for rotated pipe fill passes.

7. All position, gas shielded flux-cored wires for fill passes, typically made in the overhead and vertical up positions.

8. All position gas shielded flux cored wires designed for vertical down welds

9. Gas tungsten arc or the plasma welding process.

10. Twin MIG or metal cored wires

11. The Miller RMD a short circuit mode in which for a given wire feed rate provides less current.

12. The Fronius CMT process, another modified short circuit mode

With the 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.

Ed testing short circuit on the pipe root.

A Perspective on MIG and Flux Cored Weld Automation:

Each 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.

The prime factor for poor automated weld quality or productivity performance is again
a "lack of weld process expertise

To fully optimize either the mechanized or manual MIG or flux-cored wire processes, weld decision-maker needs to:

A. Be aware of the weld process fundamentals.

B. Be knowledgeable of the electrode wire weld parameter ranges, and the parameter relationship with the weld equipment controls.

C. Be aware of the primary feature benefits and disadvantages of each weld process and consumable utilized.

D. Understand that the primary method for weld cost control comes from understanding the wire feed and weld deposition relationship.

E. Understand the relationship between weld current, wire diameter and part thickness

Nondestructive 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.

Weld 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.

 

 

 

 

 

There 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 orbital systems.

 

IN 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.

 

After 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:

1. A reduction in weld start and stops from more than 100 to 12

2. Consistent mechanized weaves that optimize side wall fusion on both sides of the bevel.

3. Consistent weld travel speeds that ensure consistent weld fusion.

4. 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

5. The mechanized unit allows higher wire feed rates which will increase the weld travel rates.

6. 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.

All 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 selected.

When 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".

There are Benefits of Shielded Metal Arc Electrodes For Pipe Welding:

If 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.

Many 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.

The SMAW process used for the pipe root is still the best choice if the pipe root gap or pipe dimensions vary.

For 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.

 

 

 

Pipe Line Welds and Gas Shielded Flux Cored Wires:

The 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.

The 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:

A. The wrong electrode wire diameter.
(Note, for managers and supervisors, bigger is rarely better)

B. The wrong electrode wire type. E71T-1 is not the best wire for many horizontal fillet welds.

C. The wrong gas, why use CO2 if the wire runs better and smoke is reduced with an argon mix?

D. Inappropriate welding parameters.

E. Inappropriate wire stick out and the use of unsuitable stick weld techniques.

Again 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 plants.

With optimum weld data and consumables the slag falls of by itself.

 

Flux Cored Weld Deposition Rates.

The 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 manufacturing industries.

The 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.

A 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.

For 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

The 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.

When 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.

With 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.

 

Benefits of Flux Cored Weld Current Density

The 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.

The 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.

The 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.

Flux Cored Features and Benefits.

Flux-cored-arc welding offers a number of features and benefits in contrast to the SMAW process.

1. Flux cored provides higher weld deposition rates. For this pipe project 75 percent less time was required to complete the 16 in. pipe joint.

2. 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.

3. 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%.

4. Flux cored produces smooth weld tie-ins, and reduces weld undercut potential and the need subsequent grinding.

5.Flux cored produces thicker weld layers. Less filler weld passes reduces the weld tie-ins and the potential for arc-start fusion defects.

6. Flux cored produces longer weld lengths, reducing weld tie-ins and improving productivity.

7. Flux cored weld slag is easy to remove reducing the potential for weld slag entrapment

8. Flux cored provides lower weld hydrogen content and lower potential to absorb hydrogen, this minimizes potential for hydrogen cracking issues,

9. Flux cored provides faster weld travel speeds which can result in lower weld heat input. A benefit for quenched and tempered pipe.

10. 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.

11. 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.

1. With flux cored we can use one weld procedure, a narrow wire feed / voltage range, it can be simpler to operate.

2. 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.

3. 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.

6. Flux cored is less sensitive to contaminates or arc blow.

 

 

The Cold Lake Pipe Line Welding Costs:

When 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 welding consumables.

The 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.

The 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.

The 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.

For 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.

To 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 = $32,640.

 

With 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

A 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.

The 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.

To 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.

At 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.

The 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:

1.Lower weld repair costs.

2.Ability to maintain production schedules if welders are in short supply.

3. Depending on metallurgy requirements, there is a potential to eliminate or greatly reduce the required preheat..

With 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 pipe project.

Conclusion on Cost Effective Weld Choices

As 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 --

1. Pulsed MIG.
2. STT.
3. All position, gas shielded flux cored wires.
4. The stick process.
5. Traditional MIG.

There 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:

A. Simple to operate.
B. Provides superior weld fusion.
C. Requires less welding skills.
D. Provides the desired mechanical properties.
E. Provides the highest weld deposition rate potential.

Thirty 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.

The CV weld equipment utilized was developed in the 1960s.

 

Ed's Process Control flux core welding training resources, click here.

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