Selecting the appropriate piping material is a critical decision in the industrial world. The chosen material must be well-suited for the fluid it will carry and the temperature and pressure conditions it will endure. While there is a wide variety of materials to choose from, metals are commonly used in industrial piping. Mechanical strength is essential for long-term service, but extreme temperatures can pose challenges, such as low-temperature brittleness, creep, and oxidation.
Selecting the Right Piping Material for Industrial Applications
In this comprehensive guide, we will explore the processes and considerations in choosing piping materials, with a focus on ferrous and non-ferrous options.
The Significance of Ferrous Piping Materials
Worldwide, the production and consumption of iron and steel products, including tubes and pipes, constitute nearly 14% of global raw steel conversion. The production of steel tubes and pipes continues to rise to meet the demands of global industrialization and population growth. Production levels depend on various economic factors worldwide, such as oil exploration, power plant construction, and automotive production. For instance, in an economic climate with low oil prices, there is less incentive to drill new oil wells, resulting in reduced production of steel pipes for oil casing. Similar economic effects can be observed in the power generation and automotive industries. Global pipe production is an integration of the national and local economic climate worldwide.
The Ferrous Pipe Manufacturing Process
The production of steel for ferrous piping begins with the smelting of iron ore, which is found in deposits in the Earth’s crust worldwide in forms such as iron ore and magnetite. In the smelting preparation process, iron ore can be processed using several methods to transform it into a suitable form for introduction into the blast furnace. One such method is sintering, which transforms iron ore into a porous mass called clinker. Another method is smelting, which is performed in a blast furnace. This process involves a chemical reaction of iron ore with limestone, coke, and air at high temperatures, reducing the iron ore into iron. Pig iron, or crude iron, is obtained from the blast furnace explosion and is used as a fundamental component in the steelmaking process.
Steel for piping can be produced in various ways, depending on the available facilities and the desired steel characteristics. Generally, steel requires the removal of carbon from pig iron to achieve the carbon properties desired for steel. Alloy steel also requires the addition of alloying elements such as chromium, nickel, manganese, and molybdenum to provide specific properties related to the alloying elements.
The Pipe and Tube-Forming Process
There are two fundamental processes for forming pipes and tubes: seamless and welded. Each process imparts unique properties to the pipe or tube. Seamless pipes and tubes do not have welded seams along their length, which were traditionally believed to be a potential weakness. However, with the development of automated welding processes and quality control, this concern has become almost negligible. Achieving uniform wall thickness and concentricity is relatively easy with welded pipes and tubes. Generally, seamless pipes are more expensive to produce, and the classification of pipe or tube products is based on their end use.
Seamless pipes are initially produced to create hollow tubes with larger diameters and wall thicknesses than the final pipe or tube. The billet is first pierced using a rotary piercer (Mannesmann) or by the press piercing method. For small-diameter tubes, the milling mandrel process is used. For medium-sized outer diameter, low-alloy carbon steel pipes, the Mannesmann plug mill process is employed. Large-diameter, heavy-walled carbon steel, alloy, and stainless pipes are produced using the Erhardt push bench process and a vertical extrusion process similar to the Ugine Sejournet type of extrusion process. High-alloy pipes and special-shaped pipes are produced by the Ugine Sejournet extrusion type. This process is carried out with the material at hot-metal-forming temperatures. Further cold processing may or may not be performed to achieve greater dimensional accuracy, surface finish, and metallurgical structure.
Mandrel Mill Process
In the mandrel milling (pilger) process, the steel billet is heated to forging temperature and placed between the rolls of a hot rotary piercing mill. The piercing point is placed at the center of the workpiece, and the rolls are designed to advance the billet over the piercing point, thus forming a hole through the middle of the billet along its length as it moves through the inclined rolls.
Mannesmann Plug-Mill Process
In the Mannesmann plug-mill process, the billet can be pierced by two hot rotary piercers because greater reduction is required for medium-sized pipes and tubes. The pierced billet is placed in the plug mill, which reduces the diameter by rotating the tube over a mandrel. With some ovality, the tube is then inserted between rolls that provide dimensional correction and polish the inside and outside diameter of the tube. Finally, after reheating, the tube is fed back into the reeler and rolled to provide greater dimensional uniformity.
Ugine Sejournet Type Extrusion Processes
The Ugine Sejournet extrusion is used for high-alloy steel tubes, such as those in stainless steel and special-shaped pipes. Cleaned billets are heated to approximately 2300°F (1260°C) and placed in a vertical press compartment with an extrusion die at the bottom. After applying hydraulic ram pressure to the billet, the mandrel pierces the billet alongside the ram, producing a cylinder from the punched piece that exits through the extrusion die opening. Following this, the ram is activated to provide pressure on the billet, and the billet is extruded through the annulus formed between the mandrel piercer and the die cavity. In horizontal extrusion, piercing is carried out as a separate operation, or a mandrel and die are used.
Welded pipes are produced by forming a cylinder from flat steel sheets originating from a hot strip mill. The strip mill takes square blooms from a blooming mill and reduces them into plates, skelp, or coils of steel strips for input into specific welding processes. Butt-welded pipes are made by heating the furnace and forge welding or by fusion welding using electric resistance, flash, submerged-arc welding, tungsten inert gas welding, or metal-inert gas welding. The welded seam can be parallel to the tube axis or spiral along the tube’s centerline.
Cast Pipe (Ductile Iron Pipe)
There are four basic types of cast iron: white iron, gray iron, malleable iron, and soft iron. White iron is characterized by the prevalence of carbides, providing high compressive strength, hardness, and wear resistance. Gray cast iron has graphite in its microstructure, offering good machinability and resistance to wear and tear. Malleable iron is gray iron with small amounts of magnesium or cesium, resulting in graphitization of the graphite, resulting in both high strength and malleability. Soft iron is white cast iron that has been annealed to provide ductility.
Non-Ferrous Piping Materials
- Aluminum and Aluminum Alloy Tube and Pipe
Aluminum tube and pipe products include hollow products produced from hollow ingots, either through extrusion or sheet welding. Common applications are available in alloys such as 1100, 2014, 2024, 3003, 5050, 5086, 6061, 6063, and 7075. For shell and tube heat exchangers, alloys like 1060, 3003, 5052, 5454, and 6061 are used. Pipes are available in alloys 3003, 6061, and 6063. The numbers indicate specific alloying elements present in the aluminum alloy (such as copper, manganese, silicon, magnesium, and zinc) and control of impurities.
- Copper and Copper Alloy Tube and Pipe
Copper and copper alloy tubes and pipes are produced by either the piercing and extrusion process or by welding skelp into a cylindrical shape. Seamless pipes and tubes produced through the extrusion process are most widely sold.
- Nickel and Nickel-Alloy Pipe and Tube
Nickel and nickel-alloy pipes and tubes are produced using the Ugine-Sejournet extrusion process, where the shell is formed by hydraulic piercing of the billet and subsequent extrusion. Alternatively, the billet is initially pierced by drilling.
- Titanium and Titanium-Alloy Tube and Pipe
Titanium and titanium-alloy pipe and tube are produced from the smelting of raw titanium “sponge” material and alloy metals in a vacuum electric arc furnace. A billet is obtained, which is then reduced to a cylindrical shape. The process involves initially piercing the billet, passing it through a heated shell via a mold, and through a mandrel.
Selecting the right piping material is a crucial decision in industrial applications. It involves considering factors such as the media being transported, temperature and pressure conditions, and the specific needs of the industry. While ferrous materials like iron and steel remain prevalent in the industry, non-ferrous materials like aluminum, copper, nickel, and titanium also play essential roles in various applications.
Understanding the production processes and properties of these materials is essential in making informed decisions. Whether you’re working in the oil and gas sector, power generation, or any other industry that relies on piping systems, the choice of material will have a significant impact on the performance, safety, and longevity of your infrastructure.