What is Piping II Article, Video & Quiz #EPCLAND

What is Piping?

What is piping? In industrial settings, a piping system consists of pipes, fittings, valves, and special components used to transport fluids from one location to another. You can think of it like the water pipeline in your home that distributes water from the tank to your bathroom, kitchen, or handwash. However, piping in industry is a far more complex and expansive field than the simple water pipelines found in residential settings.

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Quiz on Piping!!

Piping Quiz

1. What is the definition of Piping?

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2. Which of the following is NOT a component of piping?

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3. What materials can pipes be made from?

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What is Piping?

Most people are familiar with plumbing as it constitutes water transportation in every home.

Piping can be defined as:

Interconnected Pipes subjected to the same set or sets of design to fulfill the purpose of fluid transportation using different flow control and measurement methods.

Piping also contains many different types of components like:

  1. Pipe fittings, eg. Elbow, Tee, Reducers, Flanges, couplings etc.
  2. Valves, eg: Gate valve, Globe valve, Ball Valve, Butterfly valve, control valve etc.
  3. Instruments, eg: Pressure indicator, Temperature indicator, Flowmeter etc.
  4. Equipment, eg: Pumps, Vessels, Heat exchanger, Ejector etc.

What is Pipe?

The main part of any piping system is Pipes which are used to convey materials. Pipes can be defined as: “A metallic or non-metallic cylinder used to convey fluids or transmit fluid pressure.” A pipe is normally a tubular section but its shape is not restricted to a circle. Pipes are made out of Metals, Ceramics, Plastics, concrete, and fiberglass.

Typically, metal pipe is made of Steel or Iron such as Carbon steel, Stainless steel, galvanized steel, ductile iron, brass, and alloy steel. Used of different metal pipe are designed as per pressure and fluid flowing through it. There are some terms related to pipes that are important to know by all piping engineers. Generally, Pipes for any pipe system to be used as per design and Piping standard codes.

What is Nominal Pipe Size (NPS)?

Pipe size is measured with this unit. A 4-inch pipe has never a dimension of 4 inches. Instead, its outer diameter is fixed at 4.5 inches and the inner diameter can vary depends on the thickness of the pipe. Nominal pipe size is neither OD nor ID of pipe. Manufacturing of NPS 1/8 inch to NPS 12″ pipe is done with a fixed pipe outside diameter. So, any increase in wall thickness is resulted in to decrease in Pipe inside diameter.

Manufacturing of NPS 14 and above size pipe, OD has the same value of Nominal size of the pipe. For example, a 16″ NPS pipe will have an OD of 16″ only.

Table for Pipe Outer diameter

SL. NO.Nominal Pipe SizeOuter Diameter

NOTE: This is to note that after 14″ pipe size, its outer diameter and NPS have the same value.

Quiz on Piping Diameter!!

Pipe DN and Schedule Quiz

1. What is pipe DN (Diameter Nominal)?

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2. What is Pipe Schedule?

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What is Pipe Nominal Bore (NB)?

NPS is a frequently used term for referring to the size of a pipe.  Basically, there is no difference between NB and NOS. NB is just an American way to refer to pipe size.

What is pipe DN (Diameter Nominal)?

DN or Diameter Nominal is an International indication and also the European equivalent of NPS to indicate pipe size. Here you have to note that DN is the way to indicate pipe size in “mm”. For example, 4″ pipe is simply mean as DN 100

What is Pipe Schedule?

The unit of wall thickness measurement for a pipe is “Schedule“. This is the standard method to define the thickness of pipe in the process plants. To simplify the piping thickness indication system ASME (American Society of Mechanical Engineers) committee has developed a “Schedule Number” system based on modified Barlow’s wall thickness formula.

Schedule number = P/S

  • is the service pressure in (psi)
  • is the allowable stress in (psi)

So, what does Schedule 80 means?

Schedule 80 is nothing but a pipe thickness indicator. In simple words, You can say that for a given material schedule 80 pipes can withstand a certain amount of pressure and stress.

Quiz on Pipe Schedule!!

Piping and Plumbing Quiz

1. What is the main difference between piping and plumbing?

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2. What do SRL and DRL stand for in piping engineering?

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What is the Difference between Piping and Plumbing?

While Piping and plumbing share many similarities the ultimate difference lies in the purpose of the piping system and plumbing. To know if it is piping or plumbing you have to determine by examining the pipe and its connected endpoints. i.e. From where it is connected and where the fluid goes.

  • The plumbing system transports water into facilities and provides safe drainages for water and wastewater.
  • A piping System moves chemicals, gases, water, and many other fluids to support a system of manufacturing or processing operation.

What is SRL and DRL?

In piping engineering, SRL and DRL stand for “Single Random Length” and “Double Random Length” respectively. These terms are used to specify the standard lengths of pipes.

  1. Single Random Length (SRL): This refers to pipes that have a random length typically ranging from 16 to 25 feet (4.8 to 7.6 meters). The exact length can vary based on the manufacturer, but it’s usually within this range. SRL pipes are commonly used for various industrial applications where specific lengths are not required.
  2. Double Random Length (DRL): DRL pipes are twice the length of SRL pipes, typically ranging from 32 to 40 feet (9.6 to 12.2 meters). Similar to SRL pipes, the exact lengths can vary based on manufacturer specifications. DRL pipes are often used in applications where longer lengths are needed to reduce the number of joints and connections, which can help improve the overall integrity and strength of the piping system.

Both SRL and DRL pipes are widely used in various industries such as oil and gas, petrochemical, power generation, and construction. The choice between SRL and DRL pipes depends on factors such as project requirements, transportation considerations, and installation preferences.

  1. Complete Course on Piping Engineering
  2. Basics of Piping Engineering
  3. Piping Layout Engineering
  4. Piping Material Engineering 
  5. Piping Stress Analysis
  6. Material Requisitions & TBE
  7. Piping Material Specifications
  8. Valve Material Specifications
  9. Plant Design & Layouts-OISD 118
  10. Isometric Management

Other relevant Links:

  1. Click here to check the published courses on Piping Engineering
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  4. Click here to Join the Telegram Community of Piping Professionals
  5. Click here to Prepare for PMP (Project Management Professionals) for Free

Frequently Asked Questions (FAQs)


Q1: What is piping?
A1: Piping refers to the system of pipes used to transport fluids (liquids and gases) from one location to another. Piping systems are commonly used in industries such as oil and gas, water treatment, power generation, and chemical processing.

Q2: What materials are commonly used for piping?
A2: Common materials for piping include steel (carbon steel, stainless steel), copper, plastic (PVC, CPVC, PE), and ductile iron. The choice of material depends on the application, the type of fluid being transported, and the operating conditions (temperature, pressure, and corrosiveness).

Nominal Pipe Size (NPS)

Q3: What is Nominal Pipe Size (NPS)?
A3: Nominal Pipe Size (NPS) is a dimensionless designation used to identify the size of a pipe. It is based on the pipe’s diameter but does not correspond directly to the actual outer diameter (OD) or the inner diameter (ID) of the pipe.

Pipe Outer Diameter

Q4: What is the outer diameter (OD) of a pipe?
A4: The outer diameter (OD) of a pipe is the measurement of the pipe’s diameter from the outside edge to the opposite outside edge. It is a critical dimension used for fitting and joining pipes together.

Pipe Nominal Bore (NB)

Q5: What is Nominal Bore (NB)?
A5: Nominal Bore (NB) is another term for Nominal Pipe Size (NPS), commonly used in the UK and some other countries. It refers to the approximate internal diameter of the pipe and is used to classify the pipe size.

Pipe DN (Diameter Nominal)

Q6: What is Diameter Nominal (DN)?
A6: Diameter Nominal (DN) is a European designation for pipe size, equivalent to the Nominal Pipe Size (NPS) used in North America. DN is typically followed by a number that indicates the approximate internal diameter in millimeters.

Pipe Schedule

Q7: What is pipe schedule?
A7: Pipe schedule is a measure of the wall thickness of a pipe. It is denoted by a schedule number, such as Schedule 40 or Schedule 80. Higher schedule numbers indicate thicker walls and higher pressure ratings.

Q8: How do you determine the pipe schedule?
A8: The pipe schedule can be determined from tables that list the corresponding wall thicknesses for each schedule number and nominal pipe size. These tables are standardized and can be found in piping codes and standards.

Difference between Piping and Plumbing

Q9: What is the difference between piping and plumbing?
A9: Piping generally refers to the system of pipes used in industrial and commercial applications to transport fluids and gases. Plumbing refers to the system of pipes used in residential and commercial buildings to convey water for drinking, heating, and sanitation.


Q10: What are SRL and DRL in piping?
A10: SRL stands for Standard Random Length, typically ranging from 5 to 7 meters (16.4 to 23 feet). DRL stands for Double Random Length, typically ranging from 11 to 13 meters (36 to 42 feet). These terms indicate the standard lengths in which pipes are supplied.