The manufacture of steel pipe dates from the early 1800’s. Initially, pipe was manufactured by hand – by heating, bending, lapping, and hammering the edges together. The first automated pipe manufacturing process was introduced in 1812 in England. Manufacturing processes have continually improved since that time. Some popular pipe manufacturing techniques are described below.
The use of lap welding to manufacture pipe was introduced in the early 1920’s. Although the method is no longer employed, some pipe that was manufactured using the lap welding process is still in use today.
In the lap welding process, steel was heated in a furnace and then rolled into the shape of a cylinder. The edges of the steel plate were then “scarfed”. Scarfing involves overlaying the inner edge of the steel plate, and the tapered edge of the opposite side of the plate. The seam was then welded using a welding ball, and the heated pipe was passed between rollers which forced the seam together to create a bond.
The welds produced by lap welding are not as reliable as those created using more modern methods. The American Society of Mechanical Engineers (ASME) has developed an equation for calculating the allowable operating pressure of pipe, based on the type of manufacturing process. This equation includes a variable known as a “joint factor”, which is based on the type of weld used to create the seam of the pipe. Seamless pipes have a joint factor of 1.0. Lap welded pipe has a joint factor of .6.
Electric resistance welded (ERW) pipe is manufactured by cold-forming a sheet of steel into a cylindrical shape. Current is then passed between the two edges of the steel to heat the steel to a point at which the edges are forced together to form a bond without the use of welding filler material. Initially this manufacturing process used low frequency A.C. current to heat the edges. This low frequency process was used from the 1920’s until 1970. In 1970, the low frequency process was superseded by a high frequency ERW process which produced a higher quality weld.
Over time, the welds of low frequency ERW pipe was found to be susceptible to selective seam corrosion, hook cracks, and inadequate bonding of the seams, so low frequency ERW is no longer used to manufacture pipe. The high frequency process is still being used to manufacture pipe for use in new pipeline construction.
Electric flash welded pipe was manufactured beginning in 1927. Flash welding was accomplished by forming a steel sheet into a cylindrical shape. The edges were heated until semi-molten, then forced together until molten steel was forced out of the joint and formed a bead. Like low frequency ERW pipe, the seams of flash welded pipe are susceptible to corrosion and hook cracks, but to a lesser extent than ERW pipe. This type of pipe is also susceptible to failures due to hard spots in the plate steel. Because the majority of flash welded pipe was produced by a single manufacturer, it is believed these hard spots occurred due to accidental quenching of the steel during the manufacturing process used by that particular manufacturer. Flash welding is no longer used to manufacture pipe.
Similar to other pipe manufacturing processes, the manufacture of Double Submerged Arc Welded Pipe involves first forming steel plates into cylindrical shapes. The edges of the rolled plate are formed so that V-shaped grooves are formed on the interior and exterior surfaces at the location of the seam. The pipe seam is then welded by a single pass of an arc welder on the interior and exterior surfaces (hence double submerged). The welding arc is submerged under flux.
The advantage of this process is that welds penetrate 100% of the pipe wall and produce a very strong bond of the pipe material.
Seamless pipe has been manufactured since the 1800’s. While the process has evolved, certain elements have remained the same. Seamless pipe is manufactured by piercing a hot round steel billet with a mandrel. The hollowed steel is than rolled and stretched to achieve the desired length and diameter. The main advantage of seamless pipe is the elimination of seam-related defects; however, the cost of manufacture is greater.
Early seamless pipe was susceptible to defects caused by impurities in the steel. As steel-making techniques improved, these defects were reduced, but they have not been totally eliminated. While it seems that seamless pipe would be preferable to formed, seam-welded pipe, the ability to improve characteristics desirable in pipe is limited. For this reason, seamless pipe is currently available in lower grades and wall thicknesses than welded pipe.
Conclusion
Continual advances in materials and welding techniques have resulted in dramatic improvements in the reliability of pipes. As mentioned, however, there is still pipe in use that is susceptible to corrosion and seam-related defects. These defects are identified through integrity assessments and are repaired when found.
Pipe manufactured today is subject to non-destructive tests such as ultrasonic testing and x-ray, as well as pressure-testing. Each individual section of pipe must be pressure-tested by the manufacturer, and new pipelines are also pressure-tested during the actual construction process.
Date of Revision: 12012011
Steel pipes are long, hollow tubes that are used for a variety of purposes. They are produced by two distinct methods which result in either a welded or seamless pipe. In both methods, raw steel is first cast into a more workable starting form. It is then made into a pipe by stretching the steel out into a seamless tube or forcing the edges together and sealing them with a weld. The first methods for producing steel pipe were introduced in the early 1800s, and they have steadily evolved into the modern processes we use today. Each year, millions of tons of steel pipe are produced. Its versatility makes it the most often used product produced by the steel industry.
History
People have used pipes for thousands of years. Perhaps the first use was by ancient agriculturalists who diverted water from streams and rivers into their fields. Archaeological evidence suggests that the Chinese used reed pipe for transporting water to desired locations as early as 2000 B.C. Clay tubes that were used by other ancient civilizations have been discovered. During the first century A.D, the first lead pipes were constructed in Europe. In tropical countries, bamboo tubes were used to transport water. Colonial Americans used wood for a similar purpose. In 1652, the first waterworks was made in Boston using hollow logs.
Development of the modern day welded steel pipe can be traced back to the early 1800s. In 1815, William Murdock invented a coal burning lamp system. To fit the entire city of London with these lights, Murdock joined together the barrels from discarded muskets. He used this continuous pipeline to transport the coal gas. When his lighting system proved successful a greater demand was created for long metal tubes. To produce enough tubes to meet this demand, a variety of inventors set to work on developing new pipe making processes
An early notable method for producing metal tubes quickly and inexpensively was patented by James Russell in 1824. In his method, tubes were created by joining together opposite edges of a flat iron strip. The metal was first heated until it was malleable. Using a drop hammer, the edges folded together and welded. The pipe was finished by passing it through a groove and rolling mill.
Russell’s method was not used long because in the next year, Comelius Whitehouse developed a better method for making metal tubes. This process, called the butt-weld process is the basis for our current pipe-making procedures. In his method, thin sheets of iron were heated and drawn through a cone-shaped opening. As the metal went through the opening, its edges curled up and created a pipe shape. The two ends were welded together to finish the pipe. The first manufacturing plant to use
Welded pipe is formed by rolling steel strips through a series of grooved rollers that mold the material into a circular shape. Next, the unwedded pipe passes by welding electrodes. These devices seal the two ends of the pipe together.
Welded pipe is formed by rolling steel strips through a series of grooved rollers that mold the material into a circular shape. Next, the unwedded pipe passes by welding electrodes. These devices seal the two ends of the pipe together.
This process in the United States was opened in 1832 in Philadelphia.
Gradually, improvements were made in the Whitehouse method. One of the most important innovations was introduced by John Moon in 1911. He suggested the continuous process method in which a manufacturing plant could produce pipe in an unending stream. He built machinery for this specific purpose and many pipe manufacturing facilities adopted it.
While the welded tube processes were being developed, a need for seamless metal pipes arouses. Seamless pipes are those which do not have a welded seam. They were first made by drilling a hole through the center of a solid cylinder. This method was developed during the late 1800s. These types of pipes were perfect for bicycle frames because they have thin walls, are lightweight but are strong. In 1895, the first plant to produce seamless tubes was built. As bicycle manufacturing gave way to auto manufacturing, seamless tubes were still needed for gasoline and oil lines. This demand was made even greater as larger oil deposits were found.
As early as 1840, ironworkers could already produce seamless tubes. In one method, a hole was drilled through a solid metal, round billet. The billet was then heated and drawn through a series of dies which elongated it to form a pipe. This method was inefficient because it was difficult to drill the hole in the center. This resulted in an uneven pipe with one side being thicker than the other. In 1888, an improved method was awarded a patent. In this process the solid billed was cast around a fireproof brick core. When it was cooled, the brick was removed leaving a hole in the middle. Since then new roller techniques have replaced these methods.