Steel Pipe Manufacture

ENGL135
2/24/11
Milton Krivokuca

The use of pipe for transmission of materials dates back to early civilizations. Archaeological records show tropical climates using pipe from hollowed out bamboo to move water from streams and rivers to huts inland. Bored out wood logs and other natural components carried material from one place to another. The first record of cast iron pipe being used dates back to 1562 in Langensalza, Germany (Cast Iron Pipe Research Association, 1952). The first record of steel pipe being used was in 1815 in London England by William Murdock. Murdock used musket barrels no longer in service and joined them together to transport coal gas for coal burning lamps throughout the city of London (Romanowski, 2011). Today, two types of steel pipe exist, welded pipe and seamless pipe, with several different ways to manufacture.
Welded pipe has a welded seam along the entire length of the pipe. The seams are joined by curling, or rolling the pipe into a round shape and welding the two edges together. Many different applications exist for welded pipe. Transmission of liquids such as water, oil, and slurry are a few. Solid materials such as sand, rock, and wood chips are other applications which use welded pipe.
Structural applications also exist for welded pipe. For example; when building bridges, it is not uncommon to specify welded pipe to be used as an encasement for concrete when building bridge abutments and piers. Pipe is capped and then driven into the ground by a large diesel hammer. Once the pipe is driven to a specified depth, concrete is poured into the open end of the pipe. The pipe acts an encasement for the concrete while the concrete cures. This application is known as metal shell pile (Illinois Department of Transportation, 2002) .
Two well-known processes exist to produce welded pipe, straight seam, and spiralweld. Straight seam pipe is the most common type of pipe manufactured. Steel coil or sheet is fed into a machine which rolls the steel and joins the edges together. Once pipe is formed, the seams are welded together to create a complete cylinder. Welding is generally done automatically by the electric-resistance welded process (ERW) or the electric-fusion (arc) welded process, otherwise known as submerged arc welded process (SAW) (ASTM, 2010). The manufacture of straight seam pipe is completely automated in most circumstances. This automation has enabled pipe manufacturers to produce pipe quickly and effectively with minimal defects. Labor costs along with scrap costs are minimized. Mistakes made by the human element are lessened. Mike Estrella with Naylor Pipe Co. says when he manufactures pipe, the motto on his machine is “set it, and forget it” (Estrella, 2010). Once the machine is set correctly, the machine does the work, instead of a human. Automation of the manufacture of straight seam pipe has afforded many companies great success however; automation of straight seam pipe also has its drawbacks. Typically only industry standard sizes are available for purchase. Machine limitations do not allow for custom diameters. If a custom size is needed, pipe may need to be rolled manually to the specific diameter required. This process is long and requires more manpower when producing. An automated process that can create custom sizes is the manufacturing process called spiralweld.
Spiralweld pipe is manufactured using coils of steel. A coil of steel is a long strip of steel, uniform in width, and rolled up like a paper towel roll. Based on the width of the steel, and the pitch of the machine, any diameter can be created. Spiral pipe is manufactured by pushing the end of the strip through the machine where it then comes into contact with a shoe or roll. The shoe or roll forms the steel into a tube like shape. Since steel is fed into the machine at an angle, the edges of the strip match up to create a weld seam. Like straight seam, pipe is welded automatically using the ARC welded process (ASTM, 2010). Unlike straight seam pipe, an infinite number of sizes and lengths can be produced. Custom sizes allow customers to use less material and spend less money on projects. Customers benefit from this in two ways. One; time is saved when installing material and two; fewer components are required for installation. For example, many applications require protection from abrasive materials. These applications require pipe to be lined with a ceramic or basalt. In order to achieve the correct inside diameter (I.D.) of the basalt lining, the pipe is manufactured in larger custom sizes. For instance, Abresist Corporation’s 12” basalt lined pipe uses a 14 ½” outside diameter (O.D.) pipe size. When the pipe is lined, it creates a smaller I.D. which becomes Abresist 12” basalt lined pipe (Abresist, 1983). Without spiralweld pipe manufacturers, the 14 ½” O.D. size is not available in an automated fashion. Pipe would have to be rolled manually and this would increase the cost considerably.
Spiralweld steel pipe machines are very large, and require maintenance from time to time. Because the size of pipe is constantly changing, machines are visually and mechanically inspected with every size change. When break downs occur, simple fixes do not exist. Mike Estrella, a pipe machine operator for over 40 years with Naylor Pipe Company says, “I treat this thing like my baby, if I am good to her, she is good to me. We do not have a mechanic to call when something breaks down. We pipe machine operators are the ones who know how to take apart, and put these machines back together. Some of the pipe mills I work on are forty to fifty years old. When something breaks, you can’t just find a replacement part off a shelf. Many times parts need to be fabricated” (Estrella, 2010).
Steel pipe is a universal product used all over the world. Because America still uses the imperial system of measurement, instead of the metric, conversion can be difficult. Because spiralweld pipe can be customized to fit a customer’s exact size specifications, this conversion becomes much easier. More options become available to a spiralweld pipe user around the globe.
Both types of welded pipe can be fabricated to consumer’s exact needs such as length customization. Spiralweld pipe can be manufactured up to 100’-0” and cut to exact lengths (Naylor, 1999). When a buyer purchases 10 Pieces of 36” outside diameter (O.D.) 20’-0” long spiralweld pipe that is exactly what the buyer will get. Most of the seamless pipe on the market comes in what are called single random lengths (SRL), or double random lengths (DRL). This means when a SRL piece of seamless pipe is purchased, the length could be anywhere from 20’-0” to 21’-6”. DRL would be 40’-0” to 42’-6”. This randomness adds to cost and creates confusion on jobsites. Extra equipment including saws and welding machines are required on site creating potential safety hazards along with added cost. Extra manpower for jobs not realized in a bidding process are required.
When manufacturing welded pipe it is possible to create a larger O.D. with a lighter wall thickness. When manufacturing seamless pipe, options are limited. For instance, 36” O.D. spiralweld pipe can be manufactured with a wall thickness as light as .134” wall. (Naylor, 1999) The lightest diameter that 36” O.D. seamless pipe comes in is .312” wall. (Saginaw, 2010) .312” wall is almost two and half times heavier than .134” wall. Money is saved by using the lighter wall.
There are also handling aspects when dealing with welded pipe as opposed to seamless pipe. When wall thickness is lighter, there are more options to move pipe around the shop or jobsite. In some cases two people may be able to simply lift pipe and carry it to where it needs to be. It is virtually impossible to handle seamless pipe by hand due to the heavy wall thickness. Moving seamless pipe will require a forklift or crane which will create extra costs.
With the advent of welded pipe, there became a need for pipe which did not have a weldbead. Early on the weldbead became a weak spot of pipe. Welding was hard to control, and pipe would break open at the seam or the weld. Furthermore, the obstruction of the weld or the seam created friction spots when transmitting materials. These friction spots created wear which in turn shortened the life of the welded pipe. Industry need a type of pipe which was as strong or stronger then welded pipe, but did not have a weldbead or seam. Seamless pipe was created. Some applications of seamless pipe include oil, water and natural gas. High pressure applications such as steam and thermal transfer are also specified using seamless pipe. The transfer of the following applications can be volatile on the pipe itself. A leak of any of the above products could cause major damage or even be deadly in some instances. Because of the high corrosive nature and the safety hazards associated with transmitting these materials, seamless pipe is normally specified (ASTM, 2010).
Seamless pipe typically has two well-known processes for manufacturing, plug mill, and mandrel mill manufacturing.
Plug mills produce seamless pipe around six to sixteen inches in diameter. A solid form of steel is heated up over 2000 degrees Fahrenheit and then pierced with a billet. The piercing is then made bigger by a “rotary elongator”, and creating what is now called a bloom. A plug about the same size as the desired diameter is forced through the bloom. The bloom is then put through rollers which decrease the wall thickness. The bloom is sent through these rollers four times rotated 90 degrees each time to ensure roundness. Now the bloom has become a tube and goes through a couple of more processes evening out the desired wall thickness and diameter (GE Energy, 2010).
Mandrel mills produce pipe in diameters from one to six inches. This process is the same as the plug mill except when sent through rollers; the mandrels continuously reduce wall thickness instead of four separate passes. Further processing, similar to the plug mill continues until the specified diameter and wall thickness is achieved (GE Energy, 2010).
After processing welded pipe and seamless pipe, testing of the product must take place. Several different types of testing methods exist. The test administered will depend on the ASTM grade designated to the specific pipe produced.
Hydrostatic tests are performed by filling up pipe with water to a certain pressure, and holding the pressure for a specified amount of time. The amount of time and pressure will be determined by the ASTM specification designated to the particular piece of pipe. The consumer of pipe can also request a different pressure and length of time to test the pipe to if agreed upon by the manufacturer, and the purchaser (ASTM, 2010). The test operator visually inspects the pipe for any leaks. Once tested, pipe is furthered processed, or made available for shipment. Another test that can be performed is an ultrasonic test. An ultrasonic test uses sound waves to determine material thickness, and any defects that may be under the surface of the pipe such as porosity or incomplete welds. This type of testing can be done directly on the machine as the pipe is being produced, or can be done as a separate application (ASTM, 2010).
When manufacturing welded and seamless pipe, permissible variations of weight, size, and thickness are allowed in the United States according ASTM specifications. These variations allow the manufacturer some wiggle room when producing pipe for the consumer. Because of the very nature of the manufacturing process, to create a pipe that is exactly the right size in diameter, thickness, and length is virtually impossible. This is why variations are allowed. Not all variations are the same, and will be different based on the ASTM specification of pipe manufactured. Welded pipe and seamless pipe both have similar characteristics and uses. Many of these uses overlap however; both types have advantages over the other based on certain applications. The market is full of different types of pipe manufacture to suit every individual’s specific need.

References
Abresist. (1983, September 14). Standard Drawings. Retrieved May 8, 2010, from Abresist.com: http://www.abresist.com/PDFs/StandardsDrawing.pdf
ASTM. (2010). Annual Book Of ASTM Standards A-139/A139M - 04 Standard Specification for Electric Fusion (Arc)-Welded Steel Pipe (NPS 4 and Over)1 (Vol. 01.01). West Conshoshocken, PA, US: ASTM International.
ASTM. (2010). Annual Book Of ASTM Standards A53/A53M - 07 Standard Specification for Pipe, Steel, Black and Hot-Dipped, Zinc Coated, Welded and Seamless 1 (Vol. 01.01). West Conshoshocken, PA, US: ASTM International.
Cast Iron Pipe Research Association. (1952). Handbook of Cast Iron Pipe. Chicago.
Estrella, M. (2010, February 3). Level 6 Pipe Machine Operator. (M. Griffin, Interviewer) Chicago, IL, US.
GE Energy. (2010). Pipe Manufacturing. Retrieved February 19, 2011, from GE Energy: http://www.gepower.com/prod_serv/serv/pipeline/en/about_pipelines/pipe_mfg.htm
Illinois Department of Transportation. (2002). Standard Specifications for Road and Bridge Construction. In I. D. Transportation. Springfield: Authority of the State of Illinois.
Naylor, C. (1999, March). Naylor Pipe Catalog. Retrieved May 8, 2010, from Naylorpipe.com: http://naylorpipe.com/naylorcatalog.pdf
Nucor Corporate Office. (2010, March 10). 2009 Recycled Content of Nucor Steel Products. Retrieved June 17, 2010, from Nucor.com: http://www.nucor.com/media/Recycled_Content_Letter.pdf
Romanowski, P. (2011). Steel Pipe. Retrieved Febraury 10, 2011, from Made How: http://www.madehow.com/Volume-5/Steel-Pipe.html
Saginaw, P. (2010). Pipe Chart 1. Retrieved May 8, 2010, from Saginaw Pipe: http://www.saginawpipe.com/pipe-A-revised.pdf