What to look for in a Mobile Welder? So you need a welder??? Maybe you are needing an Iron Fence welded or a Gate Latch is broken and you need a welder? So you turn to the internet and Google "Mobile Welder".
Fifteen different Welders show up and you have to figure out whos the right guy for the job? Well one of the first things you need to ask is "Are you Certified"....? Now a lot of guys will lie and they will tell you "yes I am certified, I went to College." Taking a Vocational course does not actually make you a Certified Welder. I have owned/operated Dallas Mobile Welder for over 5 years now...and I started Welding way back in Highschool at the age of 15. I am 37 now almost 38 so that gives me roughly 22 Years of Welding Experience. Not to mention I got my "CWI" through the American Welding Society at the age of 34. So Ive been a Certified Welding Inspector now for 3 years, so at the least I think its safe to assume I know a little something about welding.
To become a Certified Welder you have to take a test in the presence of a Certified Welding Inspector and once the test is complete it has to be subjected to either "Destructive or Non Destructive Testing." Weld Tests are taken on Plate or Pipe and there are literally hundreds of different scenarios depending on the "WPS" Weld Procedure Specification. This is all depending on what the company requesting you take the test requires. Over the years Ive taken so many ranging from a 1G with backing plate, which is a flat plate test to a 6GR which is a pipe on a 45 degree angle with a restrictor plate. Once the test is performed in the presence of an AWS CWI it is then subjected to non destructive or destructive testing.
There are many Examples of Destructive and Non Destructive Weld Tests that can be administered at the companies request but Ill give you the 2 most common that I have witnesses them do in house without the use of some type of third party testing. One is considered a Destructive Weld Test and that is a "guided bend test" The way this test is performed is that once the Welder has completed the test it must be allowed to cool for 24 Hrs. Once 24 Hrs is passed the plate is taken over to a band saw and Coupons are cut from the weld test plate. A total of 4 coupons are cut from the test plate. The cap and root of the weld are then ground off smooth and the edges are knocked off the coupon as well to mitigate "weld tear points". The Coupons are then taken over to an apparatus that bends the weld test coupons into a "U-Shape". 2 "Face bends" and 2 "root bends" are then performed. In Order to have a successful test there can be no breaks larger that 1/8" anywhere in the coupon. Some Companies wont allow any breaks or discontinuities at all. An Example of a non-destructive weld test would be an "Ultrasonic Test" or "UT". This test is initially performed in the same way as the test I previously explained. The welder takes the test in the presence of a CWI and then 24 hours of cooling time is allowed. That is where the similarities end. This is a non-destructive test, that being said there is no test prep needed. This method of testing makes use of mechanical vibrations similar to sound waves but of higher frequency. A beam of ultrasonic energy is directed into the object to be tested. This beam travels through the object with insignificant loss, except when it is intercepted and reflected by a discontinuity. The ultrasonic contact pulse reflection technique is used. This system uses a transducer that changes electrical energy into mechanical energy. The transducer is excited by a high-frequency voltage, which causes a crystal to vibrate mechanically. The crystal probe becomes the source of ultrasonic mechanical vibration. These vibrations are transmitted into the test piece through a coupling fluid, usually a film of oil, called a couplant. When the pulse of ultrasonic waves strikes a discontinuity in the test piece, it is reflected back to its point of origin. Thus the energy returns to the transducer. The transducer now serves as a receiver for the reflected energy. The initial signal or main bang, the returned echoes from the discontinuities, and the echo of the rear surface of the test piece are all displayed by a trace on the screen of a cathode-ray oscilloscope. The detection, location, and evaluation of discontinuities become possible because the velocity of sound through a given material is nearly constant, making distance measurement possible, and the relative amplitude of a reflected pulse is more or less proportional to the size of the reflector.
One of the most useful characteristics of ultrasonic testing is its ability to determine the exact position of a discontinuity in a weld. This testing method requires a high level of operator training and competence and is dependant on the establishment and application of suitable testing procedures. This testing method can be used on ferrous and nonferrous materials, is often suited for testing thicker sections accessible from one side only, and can often detect finer lines or plainer defects which may not be as readily detected by radiographic testing.
Once a destructive or non-destructive weld test has been successfully completed the AWS CWI will write up a Welder Qualification. If successful the Welder Qualification Paper Work will explain the weld test administered, the weld process Used, the welders name and most importantly at the bottom of the test there will be the AWS CWI's Stamp and Signature. If a welder does not have this then for 100% he is not a certified welder and your just hiring a guy that has a machine.
Over the years I have taken countless tests, the reason being that every time you go into a shop, every time a shop gets a new contract and acquires a new customer there are new requirements, new processes, the materials chance. If there is a single qualifying variable that changes a new test is required. So, personally I have many many Weld Certifications in my possession.
Your hard earned dollars matter, so be careful who you give them to. When looking for a Mobile Welder do not hire the cheapest guy you can find, hire the most qualified reasonably priced. "The Bitterness of low quality remains long after the sweetness of low price is forgotten."
Benjamin Franklin (1706-1790) U.S. Founding Father.