Selecting a Welder for the Farm or Ranch The weather finally clears, and Wisconsin dairy farmer Al Hoffmann has 385 acres of haylage to cut and store when the chopper blower band for the silo snaps in half. Part of the 3/16 in. steel band has worn paper thin and snapped, and on this Saturday, the nearest replacement band is two days away.
Using a 200 amp Millermatic wire welder, Al saves the band by tack welding it together and then welding on a back up strip of steel. The repaired chopper blower moves more than 800 tons of haylage in the next few days...
...It's evening milking time. Al is half done with his 185 cows when a hinge breaks on the air gate in the milking parlor. Al resumes milking a few minutes later, after he repairs the gate with a portable Millermatic wire welder that runs on 115V household current.
Does every farm or ranch need two or three different types of welders? While Al wouldn't trade in any of his machines, he "can't imagine not having a wire welder. It's easy to use, makes heavy welds, yet still allows me to work on thin sheet metal. I wouldn't have even attempted to repair the chopper blower band with a Stick welder because it was so thin. It would have burned right through."
Because different applications sometimes call for different welding processes, selecting the right welder for your operation is important.
The most common welding processes used for fabricating metals are:
* Stick - Shielded Metal Arc Welding (SMAW)
* MIG - Gas Metal Arc Welding (GMAW, a wire welding process)
* Flux Cored Arc Welding - (FCAW, also a wire welding process)
* TIG - Gas Tungsten Arc Welding (GTAW)
source : http://www.welding.com/articles/bparticle9.htm
Jumat, 09 Januari 2009
Selecting a Welder for the Farm or Ranch
Safety and Scheduled Maintenance Protect Your Welding Assets
Q: What can I do to avoid electrical shocks?
A: Wet working conditions must be avoided, because water is an excellent conductor and electricity will always follow the path of least resistance. Even a person's perspiration can lower the body's resistance to electrical shock. Poor connections and bare spots on cables further increase the possibility of electrical shock, and therefore, daily inspection of these items is recommended. Equipment operators should also routinely inspect for proper ground connections.
Q: How can I inspect and maintain my Miller wire feeder?
A: Periodically inspect the electrode wire drive rolls. If dirty, remove the drive rolls and clean with a wire brush. Deformed drive rolls should be replaced. Drive rolls should be changed, adjusted or cleaned only when the wire feeder is shut off. In addition, check the inlet and outlet guides and replace if they are deformed from wire wear. Remember that when power is applied to a wire feeder, fingers should be kept away from the drive roll area.
Q: What are some important electrode safety considerations?
A: Welding power sources for use with MIG and TIG welding normally are equipped with devices that permit on/off control of the welding power output. If so, the electrode becomes electrically hot when the power source switch is ON and the welding gun switch is closed. Never touch the electrode wire or any conducting object in contact with the electrode circuit, unless the welding power source is off. Welding power sources used for shielded metal arc welding (SMAW or Stick welding) may not be equipped with welding power output on/off control devices. With such equipment, the electrode is electrically hot when the power switch is turned ON.
Q: How should I store my gas cylinders?
A: Cylinders should be securely fastened at all times. Chains are usually used to secure a cylinder to a wall or cylinder cart. When moving or storing a cylinder, a threaded protector cap must be fastened to the top of the cylinder. This protects the valve system should it be bumped or dropped.
Cylinders should not be stored or used in a horizontal position. This is because some cylinders contain a liquid which would leak out or be forced out if the cylinder was laid in a flat position. Also, welding guns and other cables should not be hung on or near cylinders. A gun could cause an arc against the cylinder wall or valve assembly, possibly resulting in a weakened cylinder or even a rupture.
Q: How can I tell if my regulator is faulty?
A: The following symptoms indicate a faulty regulator:
* Leaks - if gas leaks externally.
* Excessive Creep - if delivery pressure continues to rise with the downstream valve closed.
* Faulty Gauge - if gauge pointer does not move off the stop pin when pressurized, nor returns to the stop pin after pressure release. Do not attempt to repair a faulty regulator. It should be sent to your designated Miller repair center, where special techniques and tools are used by trained personnel.
Q: What are some tips for a safe welding environment?
A: The area surrounding the welder will be subjected to light, heat, smoke, sparks and fumes. Permanent booths or portable partitions can be used to contain light rays in one area. The heat and sparks given off are capable of setting flammable materials on fire. Therefore, welding should not be done in areas containing flammable gases, vapors, liquids or dusty locations where explosions are a possibility.
Metals with plating, coatings or paint that come near the region of the arc may give off smoke and fumes during welding. These fumes may pose a health hazard to the lungs, therefore an exhaust hood or booth should be used to remove fumes from the area.
When welding in confined spaces, such as inside tanks, large containers or even compartments of a ship, toxic fumes may gather. Also, in an enclosed room, breathable oxygen can be replaced by shielding gases used for welding or purging. Care must be taken to ensure enough clean air for breathing. In many companies, it is routine to provide welders with air masks or self-contained breathing equipment.
Q: How should an operator dress for optimum safety?
A: Gloves and clothing should be flame-resistant. Clothing made from a dark-colored, tightly woven material is best suited for welding. Gauntlet-type leather gloves should be worn to protect the hands and wrists. Shirt collars and shirt cuffs should be buttoned, and open front pockets are not advisable as they may catch sparks. Also, operators should never store matches or lighters in their pockets. Pants cuffs are not recommended, as they will also catch sparks. Tennis shoes do not qualify as adequate foot protection. High-top leather shoes or boots are absolutely necessary.
Q: Is there a daily maintenance schedule I should follow?
A: Below is a general engine drive routine daily maintenance schedule, but it should be modified according to a company's specific conditions.
By following a regimen of appropriate and thorough maintenance and safety, a welder from Miller Electric can run dependably for decades. Designed to withstand rough use, these machines use high quality components and are tested for durability.
Always refer to Miller Electric's owner's manual for a thorough explanation of safety and maintenance. This article does not give complete coverage of all the maintenance and safety issues in existence.
Maintenance Schedule Chart
8 Hours
* Wipe up oil and fuel spills immediately
* Check fluid levels (oil & fuel)
* Service the air filter (refer to engine manual for specifics)
50 Hours
* Service air filter element (refer to engine manual for specifics)
* ChClean and tighten weld terminals
100 Hours
* Change oil
* Change oil filter (refer to engine manual for specifics)
* Clean and tighten battery connections
* Clean cooling system (refer to engine manual for specifics)
200 Hours
* Replace unreadable labels (order from parts list)
* Replace fuel filter
* Check valve clearance (refer to engine manual for specifics)
250 Hours
* Check and clean spark arrestor
500 Hours
* Tape or replace cracked cables
* Clean/Set injectors (refer to engine manual for specifics)
1000 Hours
* Blow out or vacuum inside equipment. During heavy service, do this monthly.
source : http://www.welding.com/articles/bparticle8.htm
Examining Pulsed MIG (GMAW-P) Welding
A brief listing of advantages provided by pulsed MIG welding (GMAW-P) usually encourages welding technicians to see if this technology may be appropriate for their application:
* All position welding with spray-like transfer
* Travel speeds increase up to 35% over short circuit transfer
* Ability to fine tune arc wave form
* Significantly reduced spatter compared to short circuit transfer
* Minimizes distortion - compared to spray transfer
* Better bead appearance
* Lower fume emissions, when properly set up
While this process offers many advantages, it's important to evaluate your application carefully before making a move to pulsed MIG. Applications best suited for GMAW-P are those currently using short circuit transfer method for welding 14 gauge (1.8 mm) to 3/8 in. (9.5 mm) steel, either manual or automated. In these situations, GMAW-P notably increases production rates, significantly reduces spatter and improves bead appearance.
The ability to tailor the arc wave form with pulsed spray transfer lets users develop beads with improved width-to-depth ratios. For example, some people use pulsed spray transfer for the fill (and even root) passes on pipe welds because they can create a penetrating arc that produces an x-ray quality weld. Others use pulsed spray transfer for overlay work (such as a nickel or inconel jacket) because they can create a wide, flat bead that results in minimal metal dilution.
The pulsing action also reduces heat input by 20 to 80 amps compared to spray transfer. This produces less distortion and a smaller heat affected zone (HAZ). One application for pulsed spray transfer is for making critical welds on the high strength steel (HY80, HY100) used for submarine hulls, where mechanical properties cannot be degraded by excess heat.
Pulsed spray transfer permits out of position welding because there is no metal transfer during a portion of the cycle, thus giving the weld puddle a chance to freeze slightly. One company welding stainless steel switched from running flux cored wire to using solid wire with pulsed spray transfer. This allowed them to maintain high speeds in the flat position and weld in the vertical up position. The company was able to recoup its investment in the new pulsed welding equipment in four months by switching from flux cored to solid wire.
Pulsed spray GMAW is not a cure-all for every welding problem, nor can it provide all of the benefits mentioned above for every application. To determine if GMAW-P is right for you, work closely with your Miller distributor. Be sure to perform cost studies, develop welding procedures, and conduct trial runs to determine the feasibility of the process for your application.
GMAW-P is a modified spray transfer process that produces minimal spatter because the wire does not touch the weld puddle (with short circuit transfer, the wire touches the weld puddle approximately 180 - 220 times per second, creating spatter). In addition, pulsed spray transfer results in a more fluid weld puddle that wets out better. This produces better bead appearance, and it also permits higher travel speed.
source : http://www.welding.com/articles/bparticle7.htm
Aluminations - Shedding light on aluminum welding issues
Frequency, or Hz, is the number of times the AC TIG arc switches between electrode negative and electrode positive in one second. Miller's Dynasty™ 300 DX inverter-based TIG power source permits adjusting output frequency from 20 to 250 Hz. Conventional TIG machines have a frequency fixed to that of the 60 Hz primary power.
Increasing the frequency narrows the shape of the arc cone and increases the arc force. This stabilizes the arc, reduces arc wandering and provides excellent directional control over the arc. On lap and T-joints, using a higher frequency lets you establish the weld puddle exactly at the root. This can ensure good penetration, control bead width and minimize the etched zone. With a 60 Hz output on fillet welds, the wider arc dances from plate to plate. The puddle starts at the toes of the weld and flows toward the center. On some joints, you're almost compelled to over-weld to ensure penetration at the root.
source : http://www.welding.com/articles/bparticle1.htm
