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Large-scale piping system in an HVAC mechanical room Mechanical room.jpg
Large-scale piping system in an HVAC mechanical room

Within industry, piping is a system of pipes used to convey fluids (liquids and gases) from one location to another. The engineering discipline of piping design studies the efficient transport of fluid. [1] [2]


Industrial process piping (and accompanying in-line components) can be manufactured from wood, fiberglass, glass, steel, aluminum, plastic, copper, and concrete. The in-line components, known as fittings, [3] valves, and other devices, typically sense and control the pressure, flow rate and temperature of the transmitted fluid, and usually are included in the field of piping design (or piping engineering), though the sensors and automatic controlling devices may alternatively be treated as part of instrumentation and control design. Piping systems are documented in piping and instrumentation diagrams (P&IDs). If necessary, pipes can be cleaned by the tube cleaning process.

Piping sometimes refers to piping design, the detailed specification of the physical piping layout within a process plant or commercial building. In earlier days, this was sometimes called drafting, technical drawing, engineering drawing, and design, but is today commonly performed by designers that have learned to use automated computer-aided drawing or computer-aided design (CAD) software.

Plumbing is a piping system with which most people are familiar, as it constitutes the form of fluid transportation that is used to provide potable water and fuels to their homes and businesses. Plumbing pipes also remove waste in the form of sewage, and allow venting of sewage gases to the outdoors. Fire sprinkler systems also use piping, and may transport nonpotable or potable water, or other fire-suppression fluids.

Piping also has many other industrial applications, which are crucial for moving raw and semi-processed fluids for refining into more useful products. Some of the more exotic materials used in pipe construction are Inconel, titanium, chrome-moly and various other steel alloys.

Engineering sub-fields

Generally, industrial piping engineering has four major sub-fields:

Stress analysis

Process piping and power piping are typically checked by pipe stress engineers to verify that the routing, nozzle loads, hangers, and supports are properly placed and selected such that allowable pipe stress is not exceeded under different loads such as sustained loads, operating loads, pressure testing loads, etc., as stipulated by the ASME B31, EN 13480, GOST 32388, RD 10-249 or any other applicable codes and standards. It is necessary to evaluate the mechanical behavior of the piping under regular loads (internal pressure and thermal stresses) as well under occasional and intermittent loading cases such as earthquake, high wind or special vibration, and water hammer. [5] [6] This evaluation is usually performed with the assistance of a specialized (finite element) pipe stress analysis computer programs such as AutoPIPE, [7] CAEPIPE, [8] CAESAR, [9] PASS/START-PROF. [10]

In cryogenic pipe supports, most steel become more brittle as the temperature decreases from normal operating conditions, so it is necessary to know the temperature distribution for cryogenic conditions. Steel structures will have areas of high stress that may be caused by sharp corners in the design, or inclusions in the material. [11]


The material with which a pipe is manufactured often forms as the basis for choosing any pipe. Materials that are used for manufacturing pipes include:


Early wooden pipes were constructed out of logs that had a large hole bored lengthwise through the center. [13] Later wooden pipes were constructed with staves and hoops similar to wooden barrel construction. Stave pipes have the advantage that they are easily transported as a compact pile of parts on a wagon and then assembled as a hollow structure at the job site. Wooden pipes were especially popular in mountain regions where transport of heavy iron or concrete pipes would have been difficult.

Wooden pipes were easier to maintain than metal, because the wood did not expand or contract with temperature changes as much as metal and so consequently expansion joints and bends were not required. The thickness of wood afforded some insulating properties to the pipes which helped prevent freezing as compared to metal pipes. Wood used for water pipes also does not rot very easily. Electrolysis doesn't affect wood pipes at all, since wood is a much better electrical insulator.

In the Western United States where redwood was used for pipe construction, it was found that redwood had "peculiar properties" that protected it from weathering, acids, insects, and fungus growths. Redwood pipes stayed smooth and clean indefinitely while iron pipe by comparison would rapidly begin to scale and corrode and could eventually plug itself up with the corrosion. [14]


Stacking of a connected pipeline for transportation of oil products Stacking of a connected pipeline for transportation of oil products.jpg
Stacking of a connected pipeline for transportation of oil products

There are certain standard codes that need to be followed while designing or manufacturing any piping system. Organizations that promulgate piping standards include:

See also

Related Research Articles

Plumbing Systems for conveying fluids

Plumbing is any system that conveys fluids for a wide range of applications. Plumbing uses pipes, valves, plumbing fixtures, tanks, and other apparatuses to convey fluids. Heating and cooling (HVAC), waste removal, and potable water delivery are among the most common uses for plumbing, but it is not limited to these applications. The word derives from the Latin for lead, plumbum, as the first effective pipes used in the Roman era were lead pipes.

Flange External or internal ridge, or rim which provides strength

A flange is a protruded ridge, lip or rim, either external or internal, that serves to increase strength ; for easy attachment/transfer of contact force with another object ; or for stabilizing and guiding the movements of a machine or its parts. The term "flange" is also used for a kind of tool used to form flanges.

Cathodic protection Corrosion prevention technique

Cathodic protection is a technique used to control the corrosion of a metal surface by making it the cathode of an electrochemical cell. A simple method of protection connects the metal to be protected to a more easily corroded "sacrificial metal" to act as the anode. The sacrificial metal then corrodes instead of the protected metal. For structures such as long pipelines, where passive galvanic cathodic protection is not adequate, an external DC electrical power source is used to provide sufficient current.

Hydrostatic test Non-destructive test of pressure vessels

A hydrostatic test is a way in which pressure vessels such as pipelines, plumbing, gas cylinders, boilers and fuel tanks can be tested for strength and leaks. The test involves filling the vessel or pipe system with a liquid, usually water, which may be dyed to aid in visual leak detection, and pressurization of the vessel to the specified test pressure. Pressure tightness can be tested by shutting off the supply valve and observing whether there is a pressure loss. The location of a leak can be visually identified more easily if the water contains a colorant. Strength is usually tested by measuring permanent deformation of the container. Hydrostatic testing is the most common method employed for testing pipes and pressure vessels. Using this test helps maintain safety standards and durability of a vessel over time. Newly manufactured pieces are initially qualified using the hydrostatic test. They are then re-qualified at regular intervals using the proof pressure test which is also called the modified hydrostatic test. Testing of pressure vessels for transport and storage of gases is very important because such containers can explode if they fail under pressure.

Gasket Type of mechanical seal

A gasket is a mechanical seal which fills the space between two or more mating surfaces, generally to prevent leakage from or into the joined objects while under compression.

High-density polyethylene Class of polyethylenes

High-density polyethylene (HDPE) or polyethylene high-density (PEHD) is a thermoplastic polymer produced from the monomer ethylene. It is sometimes called "alkathene" or "polythene" when used for HDPE pipes. With a high strength-to-density ratio, HDPE is used in the production of plastic bottles, corrosion-resistant piping, geomembranes and plastic lumber. HDPE is commonly recycled, and has the number "2" as its resin identification code.

Cross-linked polyethylene, commonly abbreviated PEX, XPE or XLPE, is a form of polyethylene with cross-links. It is used predominantly in building services pipework systems, hydronic radiant heating and cooling systems, domestic water piping, and insulation for high tension electrical cables. It is also used for natural gas and offshore oil applications, chemical transportation, and transportation of sewage and slurries. PEX is an alternative to polyvinyl chloride (PVC), chlorinated polyvinyl chloride (CPVC) or copper tubing for use as residential water pipes.

Pipe (fluid conveyance)

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 and masses of small solids. It can also be used for structural applications; hollow pipe is far stiffer per unit weight than solid members.

Nominal Pipe Size (NPS) is a North American set of standard sizes for pipes used for high or low pressures and temperatures. "Nominal" refers to pipe in non-specific terms and identifies the diameter of the hole with a non-dimensional number. Specific pipe is identified by pipe diameter and another non-dimensional number for wall thickness referred to as the Schedule. NPS is often incorrectly called National Pipe Size, due to confusion with the American standard for pipe threads, "national pipe straight", which also abbreviates as "NPS". The European and international designation equivalent to NPS is DN, in which sizes are measured in millimetres, see ISO 6708. The term NB is also frequently used interchangeably with DN.

Victaulic is a developer and producer of mechanical pipe joining systems and is the originator of the grooved pipe couplings joining system. Victaulic is a global company with 15 major manufacturing facilities, 28 branches, and over 3600 employees worldwide. Currently, Victaulic headquarters is located in Easton, PA. John F. Malloy has served as CEO since 2002.

Piping and plumbing fitting

A fitting or adapter is used in pipe systems to connect straight sections of pipe or tube, adapt to different sizes or shapes, and for other purposes such as regulating fluid flow. These fittings are used in plumbing to manipulate the conveyance of water, gas, or liquid waste in domestic or commercial environments, within a system of pipes or tubes.

Thermowells are cylindrical fittings used to protect temperature sensors installed in industrial processes. A thermowell consists of a tube closed at one end and mounted in the process stream. A temperature sensor such as a thermometer, thermocouple, or resistance temperature detector is inserted in the open end of the tube, which is usually in the open air outside the process piping or vessel and any thermal insulation. Thermodynamically, the process fluid transfers heat to the thermowell wall, which in turn transfers heat to the sensor. Since more mass is present with a sensor-well assembly than with a probe directly immersed into the process, the sensor's response to process temperature changes is slowed by the addition of the well. If the sensor fails, it can be easily replaced without draining the vessel or piping. Since the mass of the thermowell must be heated to the process temperature, and since the walls of the thermowell conduct heat out of the process, sensor accuracy and responsiveness is reduced by the addition of a thermowell.

Hydrogen pipeline transport

Hydrogen pipeline transport is a transportation of hydrogen through a pipe as part of the hydrogen infrastructure.

Plastic pipework

Plastic pipe is a tubular section, or hollow cylinder, made of plastic. It is usually, but not necessarily, of circular cross-section, used mainly to convey substances which can flow—liquids and gases (fluids), slurries, powders and masses of small solids. It can also be used for structural applications; hollow pipes are far stiffer per unit weight than solid members.

ROHR2 is a pipe stress analysis CAE system from SIGMA Ingenieurgesellschaft mbH, based in Unna, Germany. The software performs both static and dynamic analysis of complex piping and skeletal structures, and runs on Microsoft Windows platform.

A pipe support or pipe hanger is a designed element that transfer the load from a pipe to the supporting structures. The load includes the weight of the pipe proper, the content that the pipe carries, all the pipe fittings attached to pipe, and the pipe covering such as insulation. The four main functions of a pipe support are to anchor, guide, absorb shock, and support a specified load. Pipe supports used in high or low temperature applications may contain insulation materials. The overall design configuration of a pipe support assembly is dependent on the loading and operating conditions.

ASME is a non-profit organization that continues to develop and maintains nearly 600 codes and standards in a wide range of disciplines. Some of which includes the Boiler and Pressure Vessel Code (BPVC), Elevators and Escalators, Piping and Pipelines, Bioprocessing Equipment (BPE), Nuclear Facility Applications (NQA), Process Performance Test Codes (PTC), and Valves, Flanges, Fittings and Gaskets (B16).

HDPE pipe is a type of flexible plastic pipe used for fluid and gas transfer and is often used to replace ageing concrete or steel mains pipelines. Made from the thermoplastic HDPE, its high level of impermeability and strong molecular bond make it suitable for high pressure pipelines. HDPE pipe is used across the globe for applications such as water mains, gas mains, sewer mains, slurry transfer lines, rural irrigation, fire system supply lines, electrical and communications conduit, and stormwater and drainage pipes.

Use of HDPE in nuclear power plant piping systems

Piping systems in U.S. nuclear power plants that are relied on for the safe shutdown of the plant are typically constructed to Section III of the American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel (B&PV) Code. The materials allowed by the ASME B&PV Code have been historically limited to metallic materials only. Due to the success of high density polyethylene (HDPE) in other industries, nuclear power plants in the U.S. have expressed interest in using HDPE piping in ASME B&PV Code applications. In 2008, the first U.S. nuclear power plant was approved by the United States Nuclear Regulatory Commission to install HDPE in an ASME B&PV Code safety-related system. Since then, the rules for using HDPE have been integrated into the 2015 Edition and 2017 Edition of the ASME B&PV Code. The NRC approved of the 2015 and 2017 Editions in 2020. 

A variety of non-destructive examination (NDE) techniques are available for inspecting plastic welds. Many of these techniques are similar to the ones used for inspecting metal welds. Traditional techniques include visual testing, radiography, and various ultrasonic techniques. Advanced ultrasonic techniques such as time of flight diffraction (TOFD) and phased-array ultrasonics (PAUT) are being increasingly studied and used for inspecting plastic pipeline welds. Research in the use of optical coherence tomography (OCT) and microwave reflectrometry has also been conducted.


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Further reading