During the mid-1800’s, engineers needed more steam pressure meaning greater strength piping was required. Hence the thickness of the wall of pipes grew to suit the needs.The first requirements for pressurised pipes arose in the Steam Age in the late 1700’s. During this time, the only method of manufacturing pipe was with cast iron.

These pipes were still made of cast iron and were made to individual engineer’s spec’s meaning there was no conformity.

During the American Civil War in 1862, Robert Briggs (a worker at the Pascal Iron Works in Philadelphia), attempted to standardise the mills in the Pennsylvania area into manufacturing consistent size pipes to help the war effort of the Union.

This became known as the “Briggs Standards”. By 1886 many larger manufacturers had adopted the “Briggs Standard”, especially for threaded steel pipe.

In 1919 the ASA, using the Briggs Standard Pipe Thread as it basis created the National Pipe Taper (NPT) pipe threads and published the standard complete with all taper pipe and straight pipe specifications and gaging.In 1905, the American Standards Association (ASA) was started by the American Society of Mechanical Engineers and government and military agencies, with the purpose of developing the standards could be used nationally across the USA.

The “Briggs Standards”, was eventually adopted as the American Standards in the 1920’s. The word nominal, meant just that, about, or close to.In 1927, the American Standards Association surveyed the industry, and began to use the term “Schedule” (SCH), to identify the different thicknesses of Pipe. “Nominal Bore’ and “Nominal Pipe Size”, NB and NPS is very loosely related to the inside diameter in inches, and NPS 12 and smaller pipe has outside diameter greater than the size designator. For NPS 14 and larger, the NPS is equal to 14inch.

Today the following Schedule sizes are used across the industry. SCH 5, 5S, 10, 10S, 20, 30, 40, 40S, 60, 80, 80S, 100, 120, 140, 160, STD, XS and XXS.

Download: Pipe Size Reference Chart

What is Cold Cutting?

Cold Cutting refers to cutting pipe without the use of heat from a torch (hot cutting) where open flame is used. 

Why Cold Cutting?

A series of serious incidents have contributed to the development of cold cutting technology to advance pipeline repair safety. A main contributor of these incidents is the presence of hydrocarbons (a basic building block of energy products) in pipelines that creates a potentially hazardous situation when pipeline repairs, modifications or decommissioning are needed.

Cold cutting machines are designed to eliminate the hazards associated with thermal cutting, and are increasingly being specified for their inherent safety advantages. Their development reflects the priorities in pipeline repairs as follows:

1. Safety - is first and foremost as the primary consideration before any pipeline project is planned. This covers the safety of the operators of the tools and the safety of the product flowing through the pipeline.
2. Time – time is a critical factor affecting pipeline repairs when the community is relying on you to consistently provide safe sources of water, gas and other infrastructural elements.
3. Money – there is always a budget that needs to be kept in so it is important that while cold cutting machines are both safe and save time, they need to have a good ROI.

Benefits of Cold Cutting:

• Prevention of HAZ 

  Undesirable HAZ (Heat Affected Zone)	No HAZ after cold cutting - the perfect weld prep!

  
  A significant advantage of the cold cutting process over torch cutting is the prevention of a HAZ (Heat Affected Zone).  A HAZ is created when extreme temperature such as those produced by plasma or acetylene torches, is applied to a pipe. This changes the molecular structure of metal itself and often alters its properties to detrimental effect.
• Eliminates need to grind
  Torch cutting requires a second step of hand grinding to create a suitable weld ready surface. This is a difficult, laborious and time consuming process that involves inerting the pipeline with nitrogen gas to prevent combustion. Eliminating these steps saves a considerable amount of time, cost and labour.

• Fast method
  Time is a critical factor in pipeline repairs where environmental concerns and prior experiences demonstrate that faster is better to stop or prevent leaks and spills that harm the environment. This means that any tool that can perform its task faster is well worth investing in.

• Safe
  Dangers of the open flame produced by a gas torch is eliminated. In addition, airborne contaminants that are introduced into the environment by torch cutting are no longer a potential health hazard.

Cold Cutting Machines:

Most pipeliners today specify the split frame (clamshell) rotating ring pipe cutter that splits in half to mount around the OD of inline pipe. There are various configurations of split frames available such as:

• Low Clearance models - designed to balance weight, clearance and portability issues
• Heavy Duty models - designed for large diameter or heavy wall pipe

Introduced in 1949, the Trav-L-Cutter® was the first pipe cutting machine that utilised the cold cutting method. 

Designed to crawl around the pipe on its mounting chain, the Trav-L-Cutter® utilized a high speed milling head to simultaneously cut and bevel the pipe.  The two main benefits of this were:

1. Flame was eliminated - an obvious safety benefit
2. Created precision beveled surface ready for welding

Recommended Cold Cutting Machines:

	Trav-L-Cutter The Trav-L-Cutter is ideal for severing and beveling all common pipe materials, wall thicknesses and sizes from 6” (DN150) on up. Its special milling blades, leaves the pipe ends with a fine milled finish with no heat affected zone (HAZ).
	DynaPrep The DynaPrep® Split Frame is a cold cutting tool that splits in half to mount over inline pipe. It is designed for cutting, bevelling, facing, counter boring and flange facing on heavy wall pipe including high alloy material.
	GFX 6.6 Pipe Cutting & Bevelling Machine 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.
	Large Diameter Split Frame The Large Diameter Split Frame (LDSF) is designed for cold cutting, beveling, facing and counterboring on large diameter pipes, vessels and flanges. Each machine covers a 15in (381mm) diameter range.
	Guillotine Saw Guillotine pipe saws are designed to cold cut 2” through 32” (DN50-800) pipe, as well as solids such as bar stock, rails and beams. They’re strong yet light, simple to mount, simple to operate and simply bulletproof.

Unique Features of the Split Frames:

• Machining Abilities
  Split Frames are able to cut and bevel simultaneously and are capable of machining much faster and more accurately than the milling process allows. They allow you to produce the compound bevels and complex “J” prep specified by leading welding equipment manufacturers, which cannot be done using thermal cutting and grinding.

• Complete Machining System
  Machine accessories enable the Split Frames to tackle just about any onsite machining project likely to be encountered in the field. Accessories including tool slides (that hold the tooling) and tooling (cutting bits) are available to cut, bevel, counterbore (machine the inside of the pipe) and face flanges.

• Speed & Quality of Cut
  Split Frames are designed to set up quickly, to cut quickly and to cut and bevel with great precision. Destructive cutting is easy no matter the tool used, but what really counts is the critical cut needed for fit up, nicknamed the “money cut”. This cut must be exactly correct to deliver the goods, time in and time out.

• Out-of-Round Tooling
  The pipe generally used in pipelines is a medium to large diameter pipe with relatively thin walls of about .5” (12.7mm) or less. This type of pipe is seldom perfectly round and can be egg shaped, a condition known as “out-of-round”.  To ensure consistent contact of the tooling, spring tracking or out-of-round (tool) slides are available. They use springs to locate a wheel that rides along the contour of the pipe, preventing the tooling from diving in and out of the work. Out-of-round slides also speed the set-up of the machine by making it less critical that the machine be perfectly centred on the pipe.

• Tracking Slides for Uniform Land
  The land is the most important part of the weld prep. If the land is too narrow, then the welder may burn a hole through it. If the land is too thick, there may not be proper penetration to the base metal. Tracking slides allow the creation of a uniform land, which is that portion of the weld prep that accepts the critical weld root pass. 

   

Questions? Call us on 1800 734 000

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:

Sloppy cutting

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

Pipe Beveling is primarily a process used to prepare metal pipe or tube for welding by cutting a slope on the edge of the pipe. It is used in a variety of industries, from petrochemical processing plants, to food processing and general construction.

Shops who use bevelling machines regard them as an indispensable tool in their “competitive advantage” arsenal. If you are not bevelling, it could be costing you more in terms of quality and time than you expect.

Characteristics of a good Pipe Beveling Machine

There are many ways to bevel, including hand grinding, flame cutting and machining, and there are many machines available to choose from. When choosing your machine, remember that an excellent beveling machine: 

• Is lightweight

• Is efficient
• Is easy to handle
• Requires little set-up
• Operates at a fast speed
• Is easy to adjust
• Presents no health hazards to the operator
• Has the ability to produce oxide-free cutting edges

You also need to consider what kind of bevel is best suited for your application and whether the machine in mind is best suited to this application.

We recommend the DynaPrep Split Frame, a clamshell style machine designed for cutting bevelling, facing, counter boring and flange facing on heavy wall pipe including high alloy material. This can be mounted on the OD or ID of the pipe.

Factors that affect the quality of your bevel

When deciding what beveling method to use, you need to consider the factors below that may be specified in the manufacturer’s drawings or blueprint:

1. DEGREE OF THE ANGLE
   Different angles apply to different applications. The standard bevel for most cases of beveling pipe is 37.5° angle, but this is not the same for other metal applications. The critical key to a good bevel is being able to keep that angle within the tolerance level, whatever the degree.

2. LENGTH OF THE BEVEL
   The length of the bevel (sometimes referred to as the land), refers to the length of material removed to allow the weld bead to be laid into the material. Regardless of how it is measured, accuracy is important. Having a consistent length of bevel ensures easier operation when the welding is done. It reinforces the weld and makes it stronger simply because the integrity remains the same throughout the material being weld together.

3. SPEED
   Everyone knows time is money. The less time it takes to bevel, the more money you are making or saving, so it is important you choose a technique that can be done in the fastest cycle time possible.

3. HEAT AFFECTED ZONE (HAZ)
   If the term “heat-affected zone” (HAZ) is mentioned in the weld specifications, you must avoid heating the material that is being welded together. This is because metal is produced by combining varying levels of different alloys such as chromium, magnesium and iron to comprise the required structural characteristics of the metal for a specific purpose. When heat is later applied to this metal, the micro-structural characteristics of that alloy composition can change the material you originally purchased into a different metal. This means that heating the metal by working on it can ultimately change and/or affect many other components of your operation.

5. SAFE BEVELING
   When certain metals are heated they release fumes that can be toxic. If your workers are not using proper ventilation or masks they are potentially exposed to a serious health risk.  Make sure you know what specific metals are being used when working with a heat source and monitor the fumes that are produced. This critical factor should never be overlooked nor minimized.

Recommended Pipe Beveling Machines:

Although beveling is an afterthought in many shops we recommend spending some time before investing in a pipe beveling machine to assess your needs in this area. This proves to have huge benefits in terms of saving time (hence money), preserving quality – and gaining competitive advantage. We recommend these models:

 More questions? Call us on 1800 734 000

When the question arises whether you should Torque or Tension, the answer is case-sensitive.

Both have the same objective; to create a clamping force that holds parts together. Tensioning is a better system, but not always practical, or necessary.

As Bill Washington, director of business development at FASTORQ said in an interview to Wind Systems magazine, “You want to analyze your bolted joints to determine when you need torque or tension.” “I can tell you that on many flanges, they are over-designed, and torque is fine in many cases. However, you have to use tensioners to get the bolt load you need on critical flanges.”

TORQUE 

What is Torquing?

The objective of Torquing is to stretch the bolt or stud to a predetermined load. This is accomplished by turning the nut, which pulls the shank due to the ramp angle of the threads.

Torquing causes the nut to rotate against the surface of the component which is being clamped meaning as the clamp load increases, the friction between the nut and the surface of the component increases to a predetermined amount. This method is less accurate than Tensioning.

Advantages of Torquing

• Less expensive to purchase than Tensioning equipment
• More versatile
• Usually used on smaller fasteners
• Simple to use

The “K Factor” 

Torque can do well on most jobs, but you need to consider factors that can hinder getting the proper bolt load from applied torque, such as the “K Factor,” or “nut factor.” The “K Factor” has several components all of which affect preload. These factors are:

• Rust
• Lubricant
• Contaminants
• Washers
• Bolt fit
• Surface conditions,

The Problem with “K Factor” - You can try predict the “K Factor” based on experience, but it is an experimental factor which means you can’t get ‘K’ unless you’ve already tightened the bolt and measured the bolt load. This means you know what “K” was, not what it will be, but if you don’t consider it at all you are certainly going to be wrong.

Dealing with “K Factor” - Although these machines can be costly and require extensive training, one way to deal with “K Factor” issues is to measure bold preload with an ultrasonic extensometer. A less pricey and easier option is use a Load-Indicating Washer, also known as a Direction Tension Indicator (DTI). According to Washington, people can be trained to use DTI’s within 30 seconds.

When Torque is Necessary

Although there are conditions that can affect bolt load when using torque, there are situations where torque is necessary, such as when stud tensioners cannot fit into a space. If torque is necessary, Washington recommends finding a strong and fast torque wrench as only one nut can be tightened at a time.

TENSION

What is Tensioning?

Tensioning involves stretching the bolt or stud to a predetermined load by using force to elongate the shank. This is accomplished by a pulling or pushing force created by a hydraulic cylinder. The nut can then be seated manually using a wrench. It is necessary to have some extra thread above the nut, which is used to attach the pulling cylinder, which is removed after completion.

Why Tension?

If you have a problem flange and it is critical that your bolt load is evenly distributed, tensioning is the best solution. While tensioning systems can cost up to 30 times as much as torque wrenches, tensioning is the quickest, most dependable way to attain an even bolt preload when several bolts have to be tightened on a flange.

Advantages of Tensioning

• Can cut down on or even eliminate elastic interactions and over-compression of gaskets.
• Can get rid of many of the obstacles torque faces when reaching desired preload.
• Stability and ease of control
• Highly accurate
• Very little turning force is required.

Disadvantages of Tensioning 

Downsides to stud tensioners include:

• Higher load on the first pass that can lead to over compression of gasket material.
• They require more bolt length.
• Can be expensive.
• Often only fit one size bolt.
• More expensive than other systems

What details you need to know to select a Tensioner

Tensioners must be selected specific to each application. Data that must be compiled and considered in the selection of a tensioner include:

• Bolt diameter
• Free stud protrusion length
• Nut size
• Washer thickness and diameter
• Bolt grade
• Bolt load requirement

WHAT IS BEST FOR MY APPLICATION?

Deciding whether you need torque or tension is a question of understanding your needs.

• If you need to tighten several bolts, you can use a high-end torque wrench with load-indicating washers.
• With a critical joint where you want the most precise results and an even bolt load, it’s worth spending investing in tension.

Note: If you have a problem flange and you make your decision strictly based on budget without considering performance, you’ll blow the budget trying to fix it.

Need advice? Contact SFI on 1800 734 000 or email your question to sales@sfiaust.com.au