Pipes (steel)

Infobox on Pipes (steel)
Example of Pipes (steel)
Facts
Origin	Trade in steel and steel products primarily flows: within the EU: Eastern block --> EU countries and USA EU countries --> USA Japan, Korea, India, South Africa, Brazil --> EU countries and USA
Stowage factor (in m3/t)	Highly variable, depending upon packaging, dimensions and weight, e.g.: 1.04 m³/t (steel pipes)
Humidity / moisture	Relative humidity <40 - 50%
Ventilation	Steel corrosion accelerates rapidly at relative humidity > 60%. If possible, relative humidity should be reduced to below 60% by appropriate ventilation measures.
Risk factors	Seawater damage, contamination and mechanical damage.

Pipes (steel)

Description

A pipe is a tubular section or hollow cylinder, usually but not necessarily of circular cross-section, used mainly to convey substances which can flow — liquids and gases (fluids), slurries, powders, masses of small solids. It can also be used for structural applications; hollow pipe is far stiffer per unit weight than solid members.
In common usage the words pipe and tube are usually interchangeable, but in industry and engineering, the terms are uniquely defined. Depending on the applicable standard to which it is manufactured, pipe is generally specified by a nominal diameter with a constant outside diameter (OD) and a schedule that defines the thickness. Tube is most often specified by the OD and wall thickness, but may be specified by any two of OD, inside diameter (ID), and wall thickness. Pipe is generally manufactured to one of several international and national industrial standards. While similar standards exist for specific industry application tubing, tube is often made to custom sizes and a broader range of diameters and tolerances. Many industrial and government standards exist for the production of pipe and tubing. The term "tube" is also commonly applied to non-cylindrical sections, i.e., square or rectangular tubing. In general, "pipe" is the more common term in most of the world, whereas "tube" is more widely used in the United States.

There are three processes for metallic pipe manufacture. Centrifugal casting of hot alloyed metal is one of the most prominent process. Ductile iron pipes are generally manufactured in such a fashion. Seamless (SMLS) pipe is formed by drawing a solid billet over a piercing rod to create the hollow shell. Historically seamless pipe was regarded as withstanding pressure better than other types, and was often more easily available than welded pipe. Advances since the 1970's in materials, process control and non-destructive testing allow correctly specified welded pipe to replace seamless in many applications. Welded (also Electric Resistance Welded ("ERW"), and Electric Fusion Welded ("EFW")) pipe is formed by rolling plate and welding the seam. The weld flash can be removed from the outside or inside surfaces using a scarfing blade. The weld zone can also be heat treated to make the seam less visible. Welded pipe often has tighter dimensional tolerances than seamless, and can be cheaper if manufactured in the same quantities. Large-diameter pipe (25 centimetres or greater) may be ERW, EFW or Submerged Arc Welded ("SAW") pipe.

Tubing, either metal or plastic, is generally extruded.

Metallic pipes are commonly made from steel or iron; the finish and metal chemistry are peculiar to the use, fit and form. Typically metallic piping is made of steel or iron, such as unfinished, black (lacquer) steel, carbon steel, stainless steel or galvanized steel, brass, and ductile iron. Aluminum pipe or tubing may be utilized where iron is incompatible with the service fluid or where weight is a concern; aluminum is also used for heat transfer tubing such as in refrigerant systems. Copper tubing is popular for domestic water (potable) plumbing systems; copper may be used where heat transfer is desirable (i.e. radiators or heat exchangers). Inconel, chrome moly, and titanium steel alloys are used in high temperature and pressure piping in process and power facilities. When specifying alloys for new processes, the known issues of creep and sensitization effect must be taken into account.

Pipe sizes are specified by a number of national and international standards, including API 5L, ANSI/ASME B36.10M and B36.19M in the US, BS 1600 and BS EN 10255 in the United Kingdom and Europe.

Many different standards exist for pipe sizes, and their prevalence varies depending on industry and geographical area. The pipe size designation generally includes two numbers; one that indicates the outside (OD) or nominal diameter, and the other that indicates the wall thickness.

Pipes/tubes come into two categories with regard to manipulation and carriage by sea: 1) large (unprotected/protected) diameter pipes, shipped in single pieces; 2) small diameter pipes/tubes, shipped in bundles.

1) Unprotected large diameter pipes are usually manufactured from low carbon mild steel which may, if the thickness of the plate forming the pipe is not too great, originate from a hot rolled steel coil, slit into stripes (referred to as skelp) to form the width of the plate intended to be fabricated into a pipe. The long edges of the sheet, or plate, are brought together and welded to each other so forming a pipe. Such pipes usually have a visible weld running the full length of the pipe. Another method of manufacturing such pipes is by spiral welding when a flat strip of plate is wound to form a hollow spiral tube. Adjacent edges are welded together and the pipe is formed with a spiralling weld visible along its length.
Protected large diameter pipes, made of mild steel and cast iron, are protected by the application of special coatings which may be fusion bonded epoxy coatings, polyethylene coating, neoprene, bituminous materials, coal-tar and asphalt mastics.
2) To manufacture small diameter pipes (welded pipes/tubes), a strip is cut from a hot rolled coil to the width required to form the walls of the pipe, the edges are planed to a ‘V’ shape after which the strip is curled to the form of the pipe as it passes through rolls. This brings together the two prepared edges which are welded. After fairing of the welding and clearing the inside of the pipe by forcing a plug through it, the pipe is passed through an annealing furnace, thereafter being stretch reduced to size. The pipes are then cut to length and put through an ultrasonic test. Depending on customers’ requirements the pipes may be given a protective coating, left with plain ends or threaded ends, or fitted with a sleeve, as the case may be.

Seamless pipes, sometimes referred to as ‘solid drawn pipes’ are a type of piping or tubing which is preferred for all purposes where internal pressure is high and service severe. The seamless pipe is achieved in three stages as described below. A round steel billet is removed from the furnace and the end is pierced in a rotary piercing mill. Thereafter, a mandrel is forced through the billet to transform it into a hollow cylinder. The cylinder is then put through a series of rollers so that it is elongated into a shell. There then takes place a final rolling, after reheating, to form the required size of tube. Again, depending on customers’ requirements, the pipes may be given a protective coating, left with plain ends or threaded ends as the case may be. These small diameter pipes and tubes are used in the manufacture of bicycle frames, furniture for offices and homes, gardening tools and equipment, vehicle shock absorbers and exhaust pipes, boiler and condenser tubes, frameworks for the roofs of sheds, to mention but a few.

Hollow steel bars are created by forcing a hole through the centre of a round bar in much the same way as described for solid drawn pipes. They are used for structural and machinery applications and also in the oil industry. They are considered stronger than the average pipe of comparable size.

Small diameter pipes, which might be distinguished by the fact that they are not shipped loose but in bundles, will usually have a protective coating applied. They may be greased for protection, varnished, painted or galvanised.

Applications

Uses  Domestic water systems  Pipelines transporting gas or liquid over long distances  Scaffolding  Structural steel  As components in mechanical systems such as: rollers in conveyor belts, compactors (e.g.: steam rollers), bearing casing  Casing for concrete pilings used in construction projects  High temperature or pressure manufacturing processes  The petroleum industry: oil well casing, oil refinery equipment  Delivery of fluids, either gaseous or liquid, in a process plant from one point to another point in the process  Delivery of bulk solids, in a food or process plant from one point to another point in the process  The construction of high pressure storage vessels (note that large pressure vessels are constructed from plate, not pipe owing to their wall thickness and size).