How To Pipe Welding

How To Pipe Welding - A successful pipe welding process involves a variety of elements. 

Learn about the common mistakes when MIG pipe welding and the best way to fix these issues.

How To Pipe Welding

Pipe welding fundamentals

Welders frequently have lots of questions concerning welding different kinds of pipes that range from high-pressure and high-purity pipe for the food and beverage industries, to pipe that is used in gas and oil industries. 

There are many issues with fabrication and welding of pipes that could cause issues.

Concentrating on the most fundamental aspects that influence the process of pipe welding will help you overcome these problems particularly in the field operations and pipe shops are working to train new welders to work with different materials, and improve productivity and quality. 

Learn more about the most frequent issues with pipe welding and how to address them.

Cutting corners using cutting

When working with substances such as stainless steel, which are prone to heat input and are more vulnerable to deformation a bad cut could result in an insufficient fit and lead to insufficient gaps.

Welders can then make up for it by adding more filler metal in the joint. 

This can result in distortion and decrease the resistance to corrosion of the metal base. 

Insufficient preparation of the material can lead to a longer time for welding as well as higher costs for consumables and repair possibilities. 

Be aware of the correct part fitting this means having a uniform root face (land) as well as the squareness of the pipe and bevels that are the narrow or wide. 

The consistency of these aspects ensures that filler metal is kept in place and heat flow to the joint to an absolute minimal.

Inadvertently grinding the joint prior to weld preparation

Operators may employ cutting with oxy-fuel or plasma to prepare the material to be welded. 

Both processes apply an oxide layer to the cutting edge which has to be removed prior to welding.

The oxides may remain in the welding and create porosity, inclusions or a lack of fusion, among other welding imperfections. 

It is important that the weld joint is sanded to the original material before welding and grinding the outside and inside dimensions of pipes in order to get rid of oxides and other contaminants.

Improper tacking

Tacking is essential for fitting the pipe The best practices advise cutting or feathering out the tack in order to ensure the consistency of the final welding. 

Tacks that remain in the joint are used up by the welding. 

If there's a defect in the tack or the fitter employed the wrong filler material in tacking the joint there's a possibility of weld imperfections. 

By removing the tacks, you can to eliminate this issue.

Treating joint prep in the same way for stick and MIG

Welders' training is a top priority for many businesses and shops Welders are often brought in with experience from their previous jobs to their work. 

The most common error is using similar joint prep wire welding that is utilized for TIG and stick welding.

Welders with experience and training in stick welding typically prepare the joint with a substantial landing area in order to make the gap as small as they can, while TIG welding generally uses a knife edge landing. 

TIG is also generally has a smaller gap around 1/8 inch for the root opening as opposed to a 3/32 inch opening for stick.

Comparing this with the common wire techniques that are used for pipe welding. 

This Regulated Metal Deposition (RMD) process developed by Miller will require minimum 1/8" to 5/32 inch gap, along with a small land (3/32 inch from the edge of the knife). 

Welders should focus their the heat to the bevel in order to ensure that the tie-in is properly secured to the sidewall.

It's crucial to instruct welding technicians on the particulars of each procedure so that they are aware of the different weld preparation and techniques for each procedure.

If you are using the incorrect flow rate of shielding gas or mixing

There is a belief that shielding gas with more is always better at protecting the weld. 

But, excessive use of shielding gas does is not just a waste of gas and money, but it could also lead to problems such as an increase in the agitation of the puddle and convection effects which draws oxygen in the weld and creates porosity. 

Every weld station needs to be equipped with a flow meter regulator and operators should be aware of what to do to establish and stick to the recommended flow rates.

Furthermore, purchasing the gas in a mixed form is usually superior to mixing the gas through an flow regulator. 

There are many gas shielding options to select from It is advised to read for the Welding Procedure Specification to ensure that the correct gas is employed for the task.

The wrong understanding of the importance of porosity

Power sources for welding generally don't create porosity. 

To determine the reason for porosity, welding workers should examine every connection and component starting from at the top of the gun towards the source of power. 

It is typically caused by an interruption or issue with the flow of gas and that's a good starting point. Other typical causes include weak connections, insufficient gas shielding, or poor preparation of the material that causes an increase in contaminants in the welding.

Making use of the wrong nozzle or drive roll

It is essential to select the appropriate type of drive roll that is suitable for the wire that is being employed. 

Flux-cored wires are best utilized with knurled drive roll and solid wires must be utilized using standard V drive rolls. 

If you are using copper-coated flux-cored wires, U-groove drives are recommended.

Make sure to replace the drive rolls as soon as your wire gets changed. 

If a V-shaped drive roll is used in conjunction with cored with flux the result will be in slippage of wire.

If the tension on the drive roll is tightened to accommodate this the wire core. 

A knurled drive roll and wire that is solid will scratch the outer coating of the wire. 

This will then cause a plug to the liner. If an operator is prompted to increase tension on wire is usually a sign of a problem with something else or not working, like the incorrect type of drive roll or blockage in the liner.

Selecting the right size nozzle to suit the purpose is an important aspect. 

For instance, a nozzle that has a tapered and a tapered tip is recommended for the RMD procedure, however the nozzle that is tapered will not be able to meet the requirements for gas flow of pulsed MIG and may result in an insufficient gas coverage. 

Be sure to know the nozzles that work to the specific procedure.

Selecting the incorrect MIG gun to suit the job

In the event that pulsed MIG welding is to be employed for the first time, the MIG gun should be capable of handling the greater peak amperages associated with this procedure. 

Operations typically select an MIG welding gun according to the average amp required. 

However, acquiring an MIG welding gun that is 250 amps when the application is rated at 250 amps, it means the gun will be exposed to significantly higher amps during the highest pulsing period of the cycle. 

If the gun isn't built to handle that high amperage, it will run out of fuel faster.

Similar to this, the majority of MIG guns are approved to be used with carbon dioxide 100% shielding gas. 

It is acceptable for applications where welding is done with this gas, but the amperage of the gun will decrease once mixed gas is employed and is typically the case with pipe welding.

Although less amperage MIG guns are less bulky and cost less but they might not be able to fulfill an operation's requirements for pipe welding in the long term. 

Make sure to select a gun that is with a rating that is higher than the average of the welding requirements.

You should avoid buying a machine that cannot do the job

Pipe welding is a distinct creature. 

A 250-amp welding source could offer the power and performance needed for certain pipe welding tasks however, it may not be enough power for all needed tasks.

The smaller, less costly machines are less efficient, have less duty cycles, and usually have fewer capabilities. 

If a factory or operation is committed to pipe fabrication and wishes to ensure high efficiency using higher duty cycles will assure regular utilization. 

This is how much power you can use working at 20 percent duty cycle (two minutes of welding within 10 minutes) against 250 amps at 100 percent work cycle (10 minutes continuous welding over a 10-minute cycle).

Miller PipeWorx 400 welding System with an optimized arc that's designed for pipe welding in fab shops is designed to deliver 400 amps with 100 percent duty cycle, which ensures an unwavering, steady continuous arc, all day long without needing to stop in the majority of situations involving process pipes. 

This is especially useful when larger diameter wires and greater wire feed speeds are required while the energy source constantly operates at higher levels of amperage. This XMT 350 FieldPro equipped with Polarity Reversing welding technology, which is rated at 350 amps with a 60 percent duty cycles is designed specifically for field welding with outstanding efficiency in the arc to enhance the quality of welding and increase productivity when welding pipe in the field.

The most robust industrial welding systems are also equipped with multi-process welding capabilities. These are typically essential in pipe welding processes that require a stick or a TIG root pass prior to switching to a wire procedure for fill, hot or cap passages. 

The ability to combine these features within one system can help decrease the time to changeover and cost and also the burden of using several items of equipment.

Pipe welding tips

Properly preparing the material and choosing the appropriate shielding gas and the right equipment are crucial to achieving the most effective results in pipe welding. 

Follow these guidelines when welding pipes either in the shop or the field will help avoid common pitfalls improving the efficiency and quality.

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