Pipes are hollow cylindrical tubes that have been utilized by mankind for thousands of years for different purposes. Pipes can be produced from almost every material, however, since the modern-day meaning of pipes requires more than only being hollow tubes that transport fluid, metals have become more popular in pipe production. As a metal alloy, steels offer a great variety of mechanical and chemical properties that can be utilized under even extreme applications, therefore today, steel pipes have been utilized in many different applications for transportation manufactural and structural purposes. Steel pipes may be produced with different grades of steel with different production methods which vary due to application requirements.
What is a Pipe?
Steel pipes are long and hollow tubes that are used for many different applications in a variety of places. Its versatility makes pipes the most often used product that is produced by the steel industry. They are commonly used to convey fluid substances that can flow, and small solid particles. Due to their high strength, they can also be utilized in underground transportation of water and gas through cities, or in construction for purposes like heating, plumping, etc. People have been utilizing and producing pipes for different purposes for thousands of years. Archeological evidence verifies that even in 2000 BC ancient agriculturists or Chinese people have utilized pipes made from different materials like wood or bamboo, for water transportation. Since the 1800s, great strides have been accomplished in the technology of steel pipes, including improving manufacturing methods, developing applications for their use, and establishment of regulations and standards that govern their certification.
How is Pipe Used?
Pipes are utilized in structures, transportation, and manufacturing. Different materials, design characteristics, and production methods for steel pipes have been developing and varying accordingly to the application.
- Structural Usage
Structural use is commonly building and construction in which the building material is commonly referred to as steel tubes. Steel tubes are used to provide additional strength and stability for especially high buildings or constructions. Two types of steel pipes are utilized in structural usage as end-bearing piles and friction piles that both have the aim of transferring the load of the building. In those applications, steel pipes are driven deep into the earth before the foundation is laid, which constitutes great support to the building especially when the ground is not secure. Another structural application of steel pipes is scaffolding poles which allow construction workers to access all areas of the building that are out of reach. They are made by linking steel tubes into each other as a cage that surrounds the building.
- Manufacturing Usage
Steel pipes are being utilized for many different purposes in manufacturing use. Guard rails are one of the most common usages to provide a safety feature for stairs and balconies, or, in street, for cyclists and pedestrians. Steel pipes can also be utilized as security bollards which are used to cordon off an area from vehicle traffic to protect people, buildings, or infrastructures. Also, steel pipes constitute an option for outdoor site furnishings. Many commercial bike racks are formed by bending steel tubes. High toughness and strength of steel make it secure against thieves.
- Transportation Usage
The most common usage of steel pipes is the transportation of products since the characteristics of the raw material is very suitable for long-term installations. As it has mentioned before, different applications require different properties, as for low-pressure applications it is not expected for a steel pipe to exhibit ultra-high-strength since it does not expose to significant loading. More specialized applications to be used in the oil and gas industry may require more stringent specifications due to the hazardous nature of the product and the possibility of increasing pressure. These requirements bring a higher cost and quality control becomes more critical.
Design Parameters
There are two types of pipes as seamless and welded seam, and both have different uses. Seamless pipes are generally thinner and lighter, thus they are most widely used in bicycle production and fluid transportation. Seamed pipes are more heavy and rigid to obtain better consistency and durability. Pipes that are used for gas transportation, electrical conduit, and plumbing are generally seamed. During production, several parameters should be controlled to maintain the required properties for the application. As an example, the diameter of a pipe is designed directly related to how it will be used. While pipes with a smaller diameter may be used for hypodermic needles, large diameter pipes may be used for transport through cities. Wall thickness is also an important parameter to control since it directly affects the pipe’s strength and flexibility. Length, coating, and end finish are also other controllable parameters that are all related to each other as will be explained later.
Steel Types Used in Pipes
- Carbon Steels
Carbon steels represent approximately 90% of total steel pipe production. They are consist of relatively lower amount of alloying elements and are generally perform weak as used alone. Since their mechanical properties and machinability are sufficient they may cost a little less and they may be preferred more for especially low-stress applications. Lack of alloying elements lowers the suitability of carbon steels for high-pressure applications and extreme conditions, so they become less durable under high loadings. The main reason to prefer carbon steels for pipes may be their advanced ductility and non-bending nature under loading. They are generally used in the automotive and marine industry, and oil and gas transportation. A500, A53, A106, A252 are carbon steel grades that can either be used as seamed or seamless.
- Alloyed Steels
The presence of alloying elements improves the mechanical properties of steel, thus pipes become more resistant to high-stress applications and high pressures. The most general alloying elements are nickel, chromium, manganese, copper, etc. which are present in the composition between 1-50 weight percent. Different amounts of different alloying elements contribute mechanical and chemical properties f the product in varying manners, therefore the chemical composition of steels is also modified accordingly to requirements of applications. Alloyed steel pipes are generally used under high loadings with unstable conditions as in the oil and gas industry, refineries, petro-chemistry and chemistry factories.
- Stainless Steels
Stainless steel can also be included in the alloyed steel family. The main alloying element in stainless steel is chromium whose fraction varies between 10-20 weight percent. The main purpose of chromium addition is to make steel gain stainless properties by preventing corrosion. Stainless steel pipes are generally utilized under extreme conditions where corrosion resistance and high strength are vital, as in the marine industry, water purification, medicine and, oil and gas industry. 304/304L and 316/316L are stainless steel grades that can be used in pipe production. While 304 grade has great corrosion resistance and strength; due to low carbon content, 316 series exhibit lower strength and can be welded.
- Galvanized Steels
Galvanized pipes are steel pipes that are treated with a zinc coating to prevent corrosion. Zinc coating keeps corrosive substances from corroding the pipe. It was once the most common type of pipe for water supply lines, but because of labor and time that goes into cutting, threading, and installing galvanized pipe, it no longer used much, except for limited use in repairs. These types of pipes are prepared from 12 mm (0.5 inches) to 15 cm (6 inches) in diameter. They are available in 6 meters (20 feet) length. However, galvanized pipe for water distribution is still seen in larger commercial applications. One important disadvantage of galvanized pipes is their 40-50 years of lifetime. Despite that zinc coating covers the surface and avoids external substances to react with steel and corrode it, if the transported substances are corrosive pipe may start corroding from inside. Therefore, it is crucial to control and upgrade galvanized steel pipes in certain periods.