Backfire is the momentary retrogression of the flame into the torch that is usually signaled by a popping sound. The flame may either extinguish or re-ignite at the end of the tip. Sustained backfire (flashback) is the retrogression of flame into the torch with continued burning inside the torch. This event can be identified by an initial popping sound followed by a squealing or hissing sound caused by continued burning inside the torch. When it occurs, the torch oxygen valve should be turned off immediately and then the fuel gas valve.
Flashback is the return of the flame through the torch and into the hose and/or regulator and can potentially cause an explosion at any point in the system. It may also reach the cylinder. This event is caused by oxygen and fuel mixing in one side of the oxy-fuel system and subsequently being ignited at the tip and by reverse flow of one gas into the other side of the system. When it occurs, the torch oxygen valve should be turned off immediately and then the fuel gas valve.
If backfire continues to occur, the torch or the tips, or both, should be removed from service for cleaning or possible repair.
Ensure you purge all of your hoses and torch passages by briefly opening and closing each torch valve.
NOTE: Mixed gases in the torch or the hose, etc. can cause a backfire or flashback. Purging must be done before each torch lighting and especially after a cylinder change.
Flame heating involves igniting fuel gases mixed with air or oxygen. Examples include flame straightening, flame hardening, hot forming and heating in conjunction with welding. The flame is used for melting purposes in flame brazing. Acetylene, propane, propylene, and natural gas are used as fuel gases for flame heating. The flame temperature and intensity depend on the fuel gases used and oxygen mixing ratio.
The immediate work area must be clean from all contaminants. This includes removal of dirt, grease, oil, rust, paint, plastic coverings, etc., from the surface of the parts being welded. The method of cleaning depends on the material to be removed and the location of the work piece. For most construction and production equipment, steam cleaning is recommended. When this is not possible, solvent cleaning can be used. Blast cleaning with abrasives is also used. For small parts, pickling or solvent dip cleaning can be used and, finally, power tool cleaning with brushes, grinding wheels, disc grinding, etc., can be employed. The time spent cleaning a weld repair area will pay off in the long run. Be sure that all solvents have been removed before applying heat.
The most widely accepted manner to light the torch is to open the fuel gas valve slightly and ignite the gas with a spark lighter. Adjust the gas until a stable flame is maintained at the end of the tip. Open the oxygen preheat valve slowly and increase the flow until the desired flame is achieved.
Rivet washing tips use a low-velocity cutting oxygen stream to blow rivets through a plate without damaging it. Burn the rivet heads off by placing the tip perpendicular to the rivet and not by trying to cut the rivet head off from the side as you will likely score and damage the base steel material. After removal of the rivet head, the rivet shank needs to be removed by mechanical means only.
The torch cutting tip contains a number of preheat flame ports and a center passage for the cutting oxygen. The preheat flames are used to heat the metal to a temperature where the metal will react with the cutting oxygen.
Acetylene cutting tips are usually manufactures with four or six preheat holes and produced to allow light, medium and heavy preheats for use with clean, dirty, or rusted plate. They are solid coppery, one piece. Rivet washing tips use a low-velocity cutting oxygen stream to blow rivets through a plate without damaging it.
Tips also are available for gouging out welds, cutting sheet metal, and other specialized uses. One-piece tips can also be used with methylacetylene-propadiene (MAP//Pro™) and propylene. They have eight preheat holes to provide the extra heat required for these gases. However, two-piece tips generally provide the best results with MAPP® gas and propylene.
Acetylene cutting tips are usually one piece with drilled and swaged flame parts.
The six outer jets of a cutting tip are for oxygen and acetylene (Preheat Flames) and the central jet carries only oxygen. The preheat flames are not intended to melt the metal, but to bring it to its ignition temperature.
Cutting tips have metal-to-metal seating, so be sure to tighten the tip nut at 9 pounds of torque. Do not over tighten.
Two-piece tips consist of an outer shell and a splined insert. The splined insert is used to eliminate the need to drill numerous preheat holes required for cooler and slower burning gases. Different spline configurations allow different fuel gases to burn more efficiently.
Cutting tips are precision-machined copper alloy parts of various designs and sizes. They are held in the cutting torch by a tip nut.
One-piece tips are used with acetylene and are madder from copper alloy to withstand the heat of the cutting process. The copper alloy is machined, drilled and swaged over special wires to produce exact holes for preheats and cutting oxygen bores. Tolerances must be controlled carefully to produce stable flames.
Always use the proper size tip for the job. Never use an over-sized tip and then cut the fuel and oxygen back to work on a small job. This may cause tip damage, overheating, backfire and flashback.
A damaged seating surface on either the tip or the head can create a dangerous condition, resulting in a backfire or flashback. This may damage the cutting torch. If the seating surface of a tip becomes damaged, do not use it. Discard the damaged tip.
The preheat flame ports and the cutting oxygen orifice are sized for the thickness range of metal that the tip is designed to cut.
When a piece is cut by an oxygen cutting process, a narrow width of metal is progressively removed. The width of the cut is called a Kerf. Kerf width is a result of the type of tip used, the tip size, the flow rate of oxygen and preheating gases and the speed of cutting.
The advantages of oxy-fuel gas cutting include: Equipment is very portable and can be used in the field. Cutting direction can be changed rapidly on a small radius during operation. Large plates can be cut rapidly in place by moving the torch rather than the plate. Equipment costs are lower than machine tools.
Natural gas produces a lower flame temperature and a lower heating efficiency. Specialty tips designed to provide a heavy preheat flame should be considered. One volume of propylene requires 3.6 volumes of torch supplied oxygen for maximum flame temperature.
When oxyacetylene gouging, equal quantities of oxygen and acetylene are used to set a near-neutral preheating flame. When the preheating flame and oxygen jet are correctly set, the gouge has a uniform profile and its surfaces are smooth.
For proper combustion during cutting, propane (C3H3) requires 4 to 4-1/2 times its volume of preheat oxygen.
Propane is used regularly for oxygen cutting in a number of plants because of its availability and its much higher total heat value (MJ/mÂł) than natural gas. For proper combustion during cutting, propane requires 4 to 4-1/2 times its volume of preheat oxygen. This requirement is offset somewhat by its higher heat value. It is stored in liquid form and easily transported to the work site.
Beveling allows a full-penetration weld (if required). It gives the torch tip access to deep-lying base metal, prepares a well-defined, uniform container for molten metal and ensures quality welds. Bevel angles and root openings are essential for adequate weld penetration in thick plates or pipes. The joint design must specify all relevant dimensions and angles. the joint design and root opening specification are both part of the weld procedure.
Rivets can be easily removed by “washing” one head off with an acetylene torch. Next, a hole is burned along the rivet longitudinal axis. Then, while still hot, the rivet can be driven out with a pin punch and a two-pound hammer. This process completely removes the rivet and leaves a clean hole in original condition.
Cutting is initiated by heating the edge of the steel to near melting point using the pre-heat jets only, then using the separate cutting oxygen valve to release the oxygen from the central jet. The steel is instantly oxidized into molten iron oxide, producing the cut. Robotic oxy-fuel cutters sometimes use a high-speed divergent nozzle. This uses an oxygen jet that opens slightly along its passage. This allows the compressed oxygen to expand as it leaves, forming a high-velocity jet that spreads less than a parallel-bore nozzle, allowing a cleaner cut. These are not used for cutting by hand since they need very accurate positioning above the work. Their ability to produce almost any shape from large steel plates gives them a secure future in shipbuilding and in many other industries.
The ideal cut is a narrow gap with a sharp edge on either side of the work piece. Overheating the work piece and thus melting through it, causes a rounded edge. Robotic oxy-fuel cutters sometimes use a high speed divergent nozzle. This uses an oxygen jet that opens slightly along its passage. This allows the compressed oxygen to expand as it leaves, forming a high-velocity jet that spreads less than a parallel-bore nozzle, allowing a cleaner cut. These are not used for cutting by hand since they need very accurate positioning above the work.
When oxy-fuel cutting, the metal is heated until it glows orange~ (1800°F= 982°C), and then a lever on the torch is pressed to pass a stream of oxygen through the work-piece to burn the steel away where the cut is desired. The iron-oxide product of this combustion process falls to the floor as dust. Once the process is started properly, there should be no globs of melted steel under the work-piece. No melting should occur.
It is often necessary to begin a cut at some point other than on the edge of a piece of metal. This technique is known as piercing. Piercing requires a larger preheat flame than the one used for an edge start. The tip should be angled and lifted up as the cutting oxygen valve is opened. The torch is held stationary until the cutting jet pierces through the plate.
Oxy-fuel gas cutting machines are either portable or stationary. Portable cutting machines are primarily used for straight line cutting. They can carry one or more heavy-duty machine torches.
To start a cut on an edge, place the preheat flames halfway over the edge, holding the end of the flame cones 1/8” above the surface of the material to be cut. When the top corner reaches a reddish yellow, the cutting oxygen valve is opened and the cutting process begins.
The oxygen fuel gas-cutting torch can be used for gouging. Special gouging tips are available and they should be selected based on the particular geometry of joint preparation. It is possible, by closely watching the cut surface, to find and follow cracks during the flame gouging operation. The edges of the cracks will show since they become slightly hotter.
For a plate thickness of ½” or more, the cutting tip should be held perpendicular to the plate. When cutting a thinner plate, the tip can be tilted in the direction of the cut. Tilting increases the cutting speed and helps prevent slag from freezing across the kerf.
Uniweld Products will have a booth at the 2016 SEMA Show on November 1 – November 4, 2016 at the Las Vegas Convention Center
Uniweld Products is looking forward to the 2016 SEMA Show that will take place November 1-3 from 9:00am – 5:00pm and November 4 from 9:00am – 4:00pm at the Las Vegas Convention Center in Las Vegas, Nevada. The SEMA Show is the premier automotive specialty products trade event in the world. It draws the industry’s brightest minds and hottest products to one place and provides attendees with educational seminars, product demonstrations, special events, networking opportunities and more.
The 2015 SEMA Show drew more than 60,000 domestic and international buyers. The displays are segmented into 12 sections, and a New Products Showcase featured nearly 2,000 newly introduced parts. Come to the show to see the latest in technology and product development for the automotive industry. Uniweld will be exhibiting at booth #16822 so be sure to stop by to see the newest products for automotive air conditioning service. Uniweld is a U.S. manufacturer based out of Ft. Lauderdale, FL. Founded in 1949, this family owned and operated company has focused its efforts on bringing cutting edge innovation and high quality tools to the HVAC industry.
This year Uniweld will be showing off their patented EZ Turn Anti-Blowback hoses. These revolutionary hoses will be demoed at the booth and attendees will get a chance to feel the difference between the EZ Turn hoses and the rest that are out there in the market. You’ve got to feel this hose to believe it! Also being featured is the HT44 Hand Torch with an ergonomic grip and swirl combustion technology. Uniweld’s manifolds are a staple in any garage. Made in the U.S.A., they are built to last and come with high quality manual or automatic couplers. Uniweld is very excited to be attending the SEMA Show this year and hopes to see you there!
Uniweld Products displayed their Smartech® Digital Manifold, UVG Digital Vacuum Gauge, and more at the 2016 AHR Mexico Tradeshow in Monterrey, Mexico.
HVACR technicians welcomed the product launch of the Smartech® Wireless Digital Manifold in Mexico, in addition to the all-new Smartech® Digital Vacuum Gauge and their full range of HVACR tools. Those HVACR tools include refrigeration manifolds, gauges, hoses, vacuum pumps, brazing equipment, handheld brazing torches, tubing tools, and nitrogen equipment, along with other related accessories for the industry. Among an additional favorite, receiving high marks from visitors to Uniweld’s booth was the EZ Turn™ Challenge and their Anti-Blowback Hose. These hoses were designed for connecting to a system quickly and easily while under pressure. Several bystanders joined in on the enthusiasm once they witnessed the EZ Turn™ Challenge.
Uniweld’s Director of International Sales, Richard Apodaca, and International Sales Executive, Mario Portillo helped introduce the Smartech® Digital Manifold. The manifold, connecting via Bluetooth with the app, clearly displays temperature and pressure readings and automatically calculates Superheat and Subcooling calculations in real-time as the temperature and pressures fluctuate. All of the guesswork is taken out of properly charging a system with the Smart Charge Zone™ feature. Color indicators signal whether the system is overcharged (red), undercharged (blue), or has an accurate “in the zone” system charge (green). Technicians can choose from 109 refrigerant types and create a custom list of their most commonly used refrigerants.
The UVG Digital Vacuum Gauge is a reliable tool that helps you work smarter, with Smartech®. It has a highly accurate sensor that provides precise vacuum readings on a large, backlit LCD display. The accuracy is 5% of Reading +/- 5 Microns. It is preloaded with several different measurements: microns, Pa, mBar, and mmHg. The UVG has a range of 0-25,000 Microns, 3330 Pa, 33.3 mBar, 25 mmHg and a resolution of 1 Micron (<1,000 Microns), .1 Pa, .001 mBar, .001 mmHg. Made to work in different environments, its operating temperatures are -10 °F to 122 °F (-12 °C to 50 °C). To eliminate false vacuum readings, the UVG has a built-in oil sensor that indicates when the gauge needs cleaning.
Supporting Uniweld, were some of Uniweld’s authorized distributors, such as RNR, GALPA, RyR, REACSA, and ROSAN, which made for a unique combination. When visitors visited distributor’s booths looking for additional information on Uniweld products, they were directed to Uniweld’s booth. When visitors attended Uniweld’s booth wanting to know where to purchase the product, they were directed to the booths of Uniweld’s authorized distributors. The success of the AHR MEXICO show finished exceeding expectations as Uniweld looks forward to participating in the 2018 AHR Mexico Show in Mexico City, Mexico at Banamex Hall.
Uniweld In Conjunction With Emerson, Tecumseh, Parker and Rectorseal Conducted Seminars hosted by Magic Aire Industries in Manila, Philippines
Over 100 HVACR technicians attended the 2 day seminars 4 – 5 August which were tied in to the 90th birthday celebration festivities of Magic Aire Industries’ founder, Manuel Co Keng Kian. Sofia Co, Principal of Magic Aire Industries hosted the seminars and festivities which extended through the weekend.
Richard Apodaca, Director International conducted Uniweld’s seminar which focused on the introduction of Uniweld’s USMAN5 SmarTech Digital Manifold. An overview was presented in understanding the traditional manifold set with analog gauges. Most gauges in the Philippines have an accuracy rate of 3-2-3, which simply can result in inaccurate pressure readings. Combine this with flutter fluctuation on the gauge’s pointer, and the inaccuracy is compounded. Add to this, manual calculations which are done to determine superheat, sub cooling and other vital data to determine the correct refrigerant charge for a system, and you can end up with systems which are improperly charged. An incorrect charge of a system leads to reduced efficiencies of the operating system and can reduce the life cycle of the system.
Understanding these principles, the attendees were excited with the features of the USMAN5 SmarTech Digital Manifold. The digital technology permits them to do away with many of the inaccuracies which occur when operating with an analog manifold set. With the added benefits of the SmarTech Digital Manifold, such as a complete 5 foot EZ Turn Anti-Blowback hose set with 3/8” vacuum hose for 3 times faster evacuation, EZ Access “T” Fitting for simplified purging and charging, attendees were very much impressed. Add to this the Smart Charge Zone offered by Uniweld which takes the guess work out of calculating the amount of refrigerant required to properly charge a system. This feature alone won over many of the attendees.
Sofia Co of Magic Aire Industries declared the seminars conducted by Uniweld, Emerson, Tecumseh, Parker and Rectorseal to be a success. From there, it was on to the festivities and celebrations honoring the 90th birthday of Mr. Manuel Co Keng Kian.