As all welders know, there are many variables that must be considered if you want to get the best weld on a section of pipe.
But regardless of whether you are welding high-pressure pipe, high purity pipe for food and beverage industries, or pipe for the oil and gas industries, there are common elements that lead to problems in pipe welding and fabrication.
Some of the elements discussed below may seem basic, but to get the best weld it is important to focus on basic variables that affect weld quality, productivity and safety. These elements are also important when training new welders or working with new materials.
COMMON MISTAKES AND HOW TO AVOID THEM:
A poor cut can lead to poor fit-up and create unnecessary gaps, (especially when working with materials prone to distortion and the effects of higher heat input, such as stainless steel and aluminum).
Some welders try compensate this by putting more filler metal (thus, heat) into the joint to fill it, but this leads to a number of problems:
- Added heat can lead to distortion
- Corrosion-resistant qualities of the base metal are reduced (when using corrosion-resistant pipe like stainless steel)
- Lack of penetration (or excessive penetration). Poor preparation leads to longer weld cycle times, higher consumable costs and potential repairs.
So, how do I avoid this? We recommend using a dedicated orbital pipe cutter to guarantee cuts within mere thousandths of an inch of the specified parameters. This precision helps ensure optimum fit-up and keeps the amount of filler and heat put into the joint at a minimum. We recommend the GFX6.6 Orbital Cutter, the ideal solution for cutting of thin-walled tubes, typical to food processing, beverage, pharmaceutical and chemical industries where it's rugged design ensures a long product life.
Incorrect landing area
Traditional Stick and TIG welders often prepare the joint with a heavy landing area and want to keep the gap as narrow as possible. However, when using the easier, more productive MIG processes, we recommend welders reduce the landing area to a knife’s edge and space the joint at approximately 1/8-inch.
Unfortunately, the wider landing area can lead to a number of problems for welders trained in Stick and TIG processes such as focusing too much heat into the edges of the weld, a lack of penetration and insufficient reinforcement on the inside of the pipe.
To avoid these problems occurring, its a good idea to train your welders to the specifics of each application and make sure they understand different weld preparation and operational techniques before they begin the weld.
Incorrect nozzle size
Different types and sizes of nozzles are required for different MIG processes. The incorrect choice of nozzle or size can result in improper gas coverage of the weld. To avoid this, know which nozzles match up with each process/variable and use them accordingly. View our range of TIG Torches and parts
Too much shielding gas
Amateur welders often make the mistake of believing “more shielding gas is better” and crank the gas wide open in the belief that they are providing more protection to the weld.
However, this technique causes a number of problems:
- Wasted shielding gas (resources and cost)
- Increased and unnecessary agitation of the weld puddle
- A convection effect that sucks oxygen into the weld and can lead to porosity.
To avoid this, fit each weld station with a flow meter and train your welders to set and adhere to the recommended flow rates.
Incorrect type or size of drive roll
It is critical that welders remember to change drive rolls as they change types of wires in their machine. (Remember: Flux-cored wires should be used with a knurled drive roll while solid wires should be used with a standard V drive roll.)
Welders who incorrectly use a standard V drive roll with flux-cored wire will usually notice the wire slipping and crank down on the drive roll tension to hold it in place. However, this crushes the cored wire.
Meanwhile, knurled drive rolls will chip off the outer coating on solid wires which results in plugging up the liner. Welders then tend to crank on the tension, only to make the problem worse.
If you find yourself having to crank on the wire tension, it is a symptom of something else wrong with the process: wrong drive roll, wrong drive roll size or clogging in the liner. To avoid this, work the process and ensure you’re using the right drive rolls.
Relying on mixing gas with flow regulators
Avoid relying on flow regulators to bleed in the proper amount of shielding gas from two separate tanks - you don’t really know what you’re getting in a mix with this method. Instead, purchase cylinders of mixed gas from reliable sources, or buy a proper mixer. This will ensure you know exactly what you’re shielding your weld with and that you’re adhering to proper weld procedures/qualifications.
Forgetting to cut out and feather tacks
While tacks left in the joint become consumed by the weld, there is a risk for defects in the weld if there is a defect in the tack or if the fitter used the wrong filler metal to tack the joint.
To get the best weld, we recommend you cut out and feather the tack to ensure consistency of the final weld. This is especially important in shops where a fitter prepares the pipe and someone else welds it.
Bad choice of MIG gun
Some welders select a MIG gun based on the average amperage of their application, however the gun is subjected to considerably higher amperages during the peak of the pulsing cycle. The selected guns are not designed for that peak amperage meaning they can burn out at a faster rate.
While welders lean towards low amperage guns because they are lighter and less expensive, the hassle is not worth it in the long run. Always choose a MIG gun rated to handle peak amperage when pulsing, as well as mixed gases.
Buying the smaller, less expensive machine
Smaller, less expensive machines come with lower duty cycles and fewer capabilities. If you are is serious about pipe fabrication and want to maintain high productivity levels, operating at higher duty cycles will ensure consistent use. It’s the difference between 250 amps at 20 percent duty cycle (2 minutes on out of a 10 minute cycle) versus 250 amps at 100 percent duty cycle (10 minutes of continuous welding in a 10-minute cycle).
The more robust industrial welding systems offer strong multi-process capabilities – critical in pipe applications where you may be running a Stick or TIG root and then switching over to a wire process for the hot, fill or cap passes. They also offer new processes, (such as RMD), that are easier for new welders to learn and become proficient at – critical as shops continue to hunt for skilled welders. Having these capabilities in one system helps reduce changeover time and costs and eliminates the hassles of using multiple pieces of equipment.
The short of it? Avoid the downfall of operating equipment that needs to spend more time resting than working by purchasing a machine that can handle the work… and then some.
We recommend the Orbitalum Orbiweld Orbital Welders when fabricating large quatities of stainless steel tube.
Watch a video of the Orbiweld S orbital welding machine in action:
Accusing welding machines of causing porosity
Welding power sources don’t cause porosity. If you are getting porosity in your weld, we recommend you recount your steps back from the point the porosity began.
Common causes of weld porosity include:
- Loose connections
- Incorrect gas used
- A new wire spool was put in
- Material prep wasn’t completed properly meaning there are oxides present in the weld
- The material was contaminated during the process
- An interruption or problem with the gas flow
Got questions about welding? Please leave a comment below or contact us on 1800 734 000