Part I: Know your tools and skills
July 11, 2006
Starting a portable GTAW business takes a lot of hard work and dedication, but it also takes the basics of knowing how to start it. It's important to learn about what equipment you need, how to set it up, and how to evaluate your welding before you take your first job.
Editor's Note: This is the first part of a four-part series on owning and operating a portable gas tungsten arc welding (GTAW) business. Part II, addresses the customer, business applications, and tips for success.
Self-employment can be rewarding, but your knowledge and skill can make it a boom or bust. And much knowledge comes only with experience.
You will learn from mistakes—like using more than 500 feet of welding cable on the job; hoisting your high-frequency unit up eight stories; or dragging your gear 150 yards through a remote wooded field—but a few tips can help make the learning process easier.
Although you may not expect to perform gas tungsten arc welding (GTAW) outside your shop's four walls, your customers may request it—and your skills and abilities will be critical. But first you must know which equipment to buy, what materials to use, and how to evaluate your welding skills.
Several tools are critical for portable GTAW and must be set up correctly.
When setting up your equipment, first assemble a set of cable pigtails. Use orange tape for cable lead orientation. Note the control and power lead hookup from the high-frequency unit.
Power Supply. This is the most expensive and most important equipment you'll need. Get an AC/DC power supply and a high-frequency module for welding aluminum and arc starting DC electrode negative (DCEN) for stainless steel.
While scratch-start may save you money, typically it isn't a good idea: The tungsten can stick to the work; you can lose your fine-dressed point for stainless steel; and, most important, the tungsten can contaminate your workpiece. Also, used equipment can be risky because you don't know how well it's been maintained.
Before choosing a power source, call customer service representatives for manufacturers you're most interested in and get part numbers and package information to help.
Equipment Setup. To conserve time, your equipment setup should be simple and convenient.
First, assemble a set of cable pigtails (approximately 2 ft.) for the machine's output studs. Use size 1/0 welding cable, a single No. 120 lug on one end to attach to the output studs of the power supply, and a female twist-lock cable connector (2-MBP-2) to the other end to connect the welding leads. Keep a spare set as well (see Figure 1).
Start with two sets of welding cable extension leads. It will be beneficial to apply a wrapping of colored electrician's tape (other than black) on each end of one of the cables of each set. This will identify cables for long leads when using DC weld power. Each cable in one set is 40 ft. long, 75 ft. in the other set. Each cable has a male and female twist-lock cable connector. When choosing length, remember that your unit needs to be portable (you don't want to carry 100 ft. of cable up two flights of stairs). Also, don't wrap the welding cable around a steel pipe in transport. The bouncing will break down the cable, and if you use it while it's still wrapped, you'll get an erratic arc at a low amperage (see Cable Basics).
|These cables are used for connection in portable GTAW: weld cable lead extensions (left); high-frequency control extension leads (top center); connection lead to the power source output stud (bottom center); a matching set of weld cable extension leads (top right); and a ground lead with male cable connector (bottom right).|
|The weld cable and ground lead connection and gas hose and regulator are connected to the high-frequency unit.|
Next, assemble a work clamp lead using 20 ft. of 1/0 welding cable with a male twist-lock cable connector on one end and the work clamp on the other end. Do the same with a 10-ft. No. 1 cable, but replace the work clamp with a 250-amp electrode holder for shielded metal arc welding (SMAW).
You'll also need three other leads between the power supply and high-frequency module:
Cable and Hose Hookup to High-frequency Module
At the input terminals of the high-frequency module, attach a 2-ft. length of 1/0 welding cable pigtail with a male twist-lock cable connector to attach to the female connector welding lead. The gas lead will screw into the gas valve of the high-frequency unit, as will the extension cord. Connect the torch and arc starter switch (foot-controlled or torch-mounted) to the front of the high-frequency unit (seeFigure 2).
Consult the owner's manual for setup compliance, as manufacturers' requirements and recommendations may deviate from these instructions.
Torch. A typical GTAW torch setup may be an HW-26 style, 25 ft. (45V62 torch hookup adapter) for 3/32- and 1/8-in. tungsten; and an HW-17 style, 25 ft. (107V57 torch hookup adapter) for 1/16-in. tungsten, long cap and button caps. Both torches are air-cooled and use the same gas cups and internal consumables. The HW-17 may be used primarily for stainless steel.
Gas cups for torches are sized by the ID in sixteenths of an inch. Welding inside corners requires a No. 4 or 5; outside corners and flat positions require a No. 7 or 8. One size doesn't fit all applications. It isn't unusual for the tungsten to protrude from the end of the cup to aid visibility and joint access, approximately 1/4 to 5/16 in.
Securing your transport is critical to safely handling your gas cylinder.
Shielding Gas. You can rent or buy your gas cylinder. The S-style cylinder, about 155 cu. ft. and 51 in. tall, is convenient because of its size. Typically, you'll want to purchase your cylinder, because it costs about the same as renting one for two years. The T style, which is about 340 cu. ft. and 60 in. tall, rarely is sold; it's usually rented.
Your gas cylinder never leaves the transport; that's why you use a gas hose. Always have a spare regulator, and for cylinder safety and security, chain it upright in the transport vehicle using a chain and padlock (see Figure 3).
Exchange the cap when you exchange your empty cylinder for a full one. Never transport a cylinder with the regulator still attached. If you hit a tree branch or overhang, the regulator or valve will break off. Within seconds, all cylinder contents will be gone; expensive regulator repair or replacement will be necessary; and cylinder valve damage will result in more unnecessary expenses.
Autodarkening Helmet. A quick-change autodarkening welding helmet can be helpful. Flipping and nodding your head to move the helmet up and down won't work for portable GTAW service work because some positions make it impractical.
Filler Metal. By the end of your business venture, you will probably have carried more than 20 alloys, but these are the basic ones you'll need:
For traveling purposes, carry only a couple pounds of each size, each grade. Take a couple lengths of 1-1/2-in. PVC pipe or tubing, cut them in 36-in. lengths, and glue a cap on one end. Label each tube for each filler metal, and store all the different diameters in one tube.
Even if you specialize in GTAW, you won't want to pass up other welding jobs. Always have a couple of pounds of electrodes for SMAW:
Always store low-hydrogen electrodes (E7018) in a 50-lb. electric dry rod box.
Transport. Truck beds and trailers are the most common transport options in portable welding; for example, a 4- by 9-ft. trailer with a 3-ft.-tall railing in the front and on one side. A trailer this size can haul your power supply; two storage boxes (7 and 9 cu. ft.); four gas cylinders; a spare tire; and a heavy-duty, 6-in., vise-mounted welding cable.
The most difficult aspect of owning and operating a welding business is evaluating your welding skills. Before you begin, first consider a few welding tips:
Now on to the self-evaluation of your skills. Remember to be honest with yourself.
Clean your filler metal and base metal thoroughly. Stainless steel wool, grade 0 or 00, is suitable. Keep filler metal free of dirt, paint, oil, grease, glue, and oxides. A metal oxide is unusable in GTAW; generally, oxides melt at a higher temperature than the base metal.
To evaluate your welding, get about 30 pieces of 4- by 6-in.-long, 0.050- to 0.068-in.-thick aluminum (stainless steel should be 0.040 to 0.062 in. thick). You'll appreciate torch control in this thickness range. Arc length is critical. Remember, as arc length increases, voltage (arc force) increases, resulting in more heat.
When evaluating your skills on aluminum, use a 1/16-in.-dia. 2 percent tungsten (red) and ball the tip. Set your amps between 70 and 90, use a 1/16-in. E4043 cleaned filler metal, and set the argon at 25 to 30 CFH.
In one piece, drill six 3/32-in. holes; in another piece, drill six 1/4-in. holes; and in the third piece, drill six 3/8-in. holes. Before you weld, brush off the aluminum oxide around each hole vigorously with a stainless steel brush. Fill three holes of each size in the flat position and three in the vertical position, letting each weld cool to the touch before welding the next one. When you see the hole edge "sweat," add filler. Do a couple of T joints (fillet welds) and butt joints in the same position, and then do a couple of inside and outside corner welds.
Now ask yourself: Would I want a repair on my pontoon tube to look like this?
For these tests, aluminum and stainless steel hole-filling welds should have a small dome contour approximately equal to the base metal thickness. After you clean the weld with a stainless steel brush, the weld and base metal should be clean and unstained by the heat application. The weld should blend in very smoothly at the weld's fusion zone. Fillet welds (T joints) should clean up to a bright, shiny finish, be flat to slightly concave in contour, and should transition smoothly from the weld to the base metal.
Make the same test joints for stainless steel, but remember that stainless steel is different from aluminum. Heat stays in the weld area longer, and compared with aluminum, stainless steel is a poor heat conductor. "Sugaring," which affects the back side of the weld and is caused by the chrome coming into contact with the air at high temperature, will be a problem.
Backpurging is the only practical way to prevent sugaring. Set your power supply at 40 to 60 amps, use a 1/16-in., pointed 2 percent tungsten (red), set your gas flow at 20 to 25 CFH, and use a 0.045- to 1/16-in.-dia. filler metal.
Control the heat so you'll finish with a smooth weld bead contour, no burning of the weld surface, and very little if any sugaring on the back side of the weld. As with aluminum, after you extinguish the arc, hold the torch over the end of the weld to allow your postflow gas to shield the hot metal for 10 to 15 seconds. Keep the filler metal right at the arc, ready to use. If the end of the filler metal is burnt black, cut it off before you use it. As with aluminum, the face of the fillet welds (the T joint) should be flat or slightly concaved. You should be able to clean all welds easily with a brush. If not, you got them too hot.
For another stainless steel evaluation, buy 1/4-in. stainless steel washers and 10 to 24 screws. Practice welding the washer flat to a test piece on the ID and weld the head of the screw flat to a test piece without burning them.