Plant Design

What is a pipe and what are the types of Pipes?

What is a Pipe?
According to the Merriam dictionary, a pipe is defined as a long tube or hollow body for conducting a liquid, gas, or finely divided solid or for structural purposes. From the engineering perspective, pipes are defined as circular tubular products used for conveying fluids (liquids, gases, and fluidized solids). For transporting fluid, pipes are designed for a particular design pressure corresponding to design temperature. Various parameters such as pipe size, pipe thickness, pipe material, pressure withstanding capability, temperature withstanding capability, etc. are considered during piping design.

Applications of Pipes:
Different types of pipes are used in the industrial sector for different purposes. Oil & gas, process industries, chemical & petrochemical industries, food & beverage industries, energy & power industries, refineries & pipeline industries, HVAC industries, steel & infrastructure industries, and daily water sewerage line requires pipes to transport fluid from one place to another. In modern life, the use of pipes is so broad that we cannot imagine any industrial process without pipes.

Types of Pipes:
Due to the application of a large number of industries and processes, the types of pipes are many. The type of pipe is chosen based on various application factors. In this article, we will discuss the different types of pipes that are widely used in industries.

1. Based on the material of the pipes

Pipes can be classified based on the material which is used to produce the pipe during manufacturing. In general, there are two types of pipes:
1. a. Metallic Pipes
1. b. Non-metallic Pipes

1.a. Metallic Pipes
The pipes which are made of metal are known as metallic pipes. They can be categorized into two categories:

1.a.1. Pipes made from ferrous materials
1.a.2 Pipes made from non-ferrous materials

1.a.1 Type of Pipes made from ferrous materials:
Pipes made from ferrous materials are stronger and heavier. These category pipes are most suitable used for heavy-duty work to transport high pressure or high temperature even sometimes heavy fluids. The common application of pipes made from ferrous material is in the oil & gas industries, chemical & petrochemical, energy & power industries, and refineries & piping industries.  These pipes have iron as their main constituent element. Common examples of pipes made from ferrous materials are-

  • Cast Iron pipes
  • Carbon steel pipes
  • Stainless steel pipes
  • Alloy steel pipes
  • Duplex Stainless Steel (DSS) pipes
  • Ductile Iron pipes and so on.

1.a.2 Type of Pipes made from Non-ferrous materials:
Although these pipes are metallic, however iron is not the main constituent of these pipes. These pipes are usually made of copper, aluminum, brass, etc. Non-ferrous material pipes are mostly used in the process piping industry. The main reason behind that is these materials have excellent tensile strength. For example, pipes made of Nickel and Nickel alloys are ideal to use in extreme heat environments because of their resistance property, and it has a passivating oxide coating on their covering. Nickel-copper, nickel- Molybdenum, and nickel-chromium are the most common alloys of Nickel. Nickel and its alloys offer resistance against corrosion and oxidation. This material is suitable to use in applications where alkalis or storing caustic soda is present. It is generally utilized in seawater and mild atmospheric applications. Common pipes made from non-ferrous materials are-

  • Copper and copper alloy pipes.
  • Aluminum and Aluminum alloy pipes.
  • Nickel and Nickel alloy pipes.
  • Titanium and titanium alloy pipes.
  • Zirconium and Zirconium alloy pipes.

1.b. Non-metallic Pipes
Non-metallic pipes are widely used for services where the temperature is not very high. Non-critical services like water industries and drainage systems make use of most of the non-metallic pipes. Common non-metallic and widely used pipes are:

  • Polyethene (PE) plastic pipe/ high-density polyethene (HDPE) Pipes
  • Polyvinyl chloride (PVC) / uPVC/ CPVC Pipes
  • PP pipes
  • Reinforced thermoplastic pipes or RTPs
  • ABS Pipes
  • Composite pipes like GRE/GRP/FRP Pipes
  • Cement and Asbestos Cement Pipes
  • Vitrified clay pipes

The main advantages of reinforced plastic and composite pipes are that they are highly corrosion resistant and durable. While metallic pipes are usually designed for up to 25 years of service. Composite and Reinforced plastic pipes can easily serve up to 50 years. However, their main limitation is the temperature. Non-metallic pipes are not suitable for high-temperature applications. Cement pipes, manufactured from reinforced concretes are usually used for stormwater, gravity service, irrigation industries, and culverts.

2. Types of Pipes based on industry application
As pipes are used in a wide range of industries, therefore these also can be classified based on the industry application. The major types of pipes based on industry applications are-

2.a. Pipes for the Plumbing industry
2.b. Pipes for Chemical and Power industries
2.c. Pipes for the Pipeline industry

2.a Types of Pipes for the Plumbing industry
Pipes are essential to supply water to the kitchen tap or to drain wastewater to the sewage system. These types of drainage and delivery systems have been around since ancient times. In modern times, the common plumbing pipes are PVC pipes, PEX pipes, Copper pipes, ABS pipes, Cast Iron and galvanized steel pipes, etc. They are mainly used for water distribution purposes.

2.b. Types of Pipes for Chemical and Power industries
These types of pipes are suitable for high-temperature and pressure applications. Mainly pipes made from ferrous materials are used in the chemical & petrochemical industries, power & energy industries, steel industries, and oil & gas industries. The chemical and power industry pipes are designed by following codes like ASME B31.3, ASME B31.1, and also other international standards and codes. They are usually selected based on their ability to sustain pressure, temperature, corrosion resistance, etc.

2.c. Pipes for the Pipeline industry
Pipes used in pipeline industries are usually known as line pipes. These pipes are designed by API 5L standard. There are various grades of API 5L pipes that are used to convey oil, gas, or water through pipelines. Other types of pipeline materials are SS, DSS, SDSS, GRE, FRP, etc.

3. Types of Pipes depending on the fluids transported

As you already know the main purpose of pipes is to transport fluids from one point to another, therefore depending on the type of fluid used to transport, pipes can be categorized as-

  • Water Pipes those transport water.
  • Gas pipes transport gaseous substances such as methane gas in the gas power plant.
  • Steam pipes transport steam such as steam in the steam power plant.
  • Vapor pipes transport different vapors of products such as vapor chemicals in the chemical industry.
  • Oil pipes transporting crude or processed oils.
  • Hydrogen pipes carrying hydrogens.

4. Types of Pipes depending on the manufacturing process
Pipes can also be classified based on the manufacturing process. These are again sub-categorized depending on the material of the pipe. For example, Metallic pipes can be categorized as-
4.a. Seamless pipes
4.b. Welded pipe
        4.b.1 Electric resistance welded (ERW) pipes
         4.b.2 Longitudinal Submerged Arc-Welding (LSAW) pipes

4.a. Seamless pipes
The most common types of seamless pipes are:

  • ASTM A106, A333, A53, and API 5L (CS and LTCS pipes)
  • ASTM A312 Series 300 and 400 (SS pipes with grades 304, 316, 321, 347)
  • ASTM A335 Grades P5 to P91 (Alloy steel pipes)
  • ASTM A790/A928 (DSS and SDSS pipes)
  • Nickel alloys (Inconel, Hastelloy, Cupronickel, Monel, Nickel 200)

In general, pipes with a diameter of less than 16 inches are seamless, and larger diameter pipes are welded. Seamless pipes are preferred due to the absence of the weld seam which is considered a weak point. However, they are costlier than welded pipes. Also, for large-diameter pipes, producing seamless pipes becomes difficult.

Carbon steel pipes (A53, A333, A106, and API 5L) have the largest market share since they are cheaper and suitable for a wide range of applications ranging from -29 Deg C to 427 Deg C.

Similarly, Glass Reinforced Plastic (GRP) pipes are classified as-

  • Filament winding GRP pipes
  • Continuous winding GRP pipes
  • Helical Filament winding GRP pipes

4.b. Welded pipe
4.b.1. Electric resistance welded (ERW) pipes
4.b.2. Longitudinal Submerged Arc-Welding (LSAW) pipes

Final Words:

Different types of pipes are used in various industries. The properties of those pipes are different based on their materials and compositions. Therefore, the types of pipes are very broad and there are various parameters that contribute to the classification of pipes. However, the most widely accepted pipe classification is based on the material used to fabricate the pipe. To buy different types of pipes you can visit Iminning Tuberia Industrial.

More to read

Crankcase ERV

What is the function of an explosion relief valve (ERV) in a crankcase?

Crankcase overpressure relief valves have three functions:

(1) Rapidly relieve excess pressure inside the crankcase
(2) Prevent flame inside the crankcase from escaping and causing further damage
(3) Rapidly close after the crankcase pressure is relieved to prevent the air from entering into the crankcase.

Figure: Crankcase overpressure relief valve operation.

The figures show that the relief valves have a light spring that holds the valve tightly against its seat. The pressure inside the crankcase is relieved, and the spring closes the valve automatically. Figures show an image of a properly operating crankcase relief valve. The valve is still closed on the left of the picture while an internal explosion is about to open. On the right, the internal pressure has forced the valve open, compressing the spring while the hot pressurized gas, but not the flame, is vented to the atmosphere. Once the pressure is relieved, the compressed spring closes the valve.

Figure: ERV in the industry.

API 618 requires a relief area to crankcase volume ratio of 3.0 in²/ft³ (683 cm² /m³), which is higher than any of the engine standards. With properly sized and installed overpressure relief valves, experience has shown that the risk of damage and injury from crankcase explosions can be eliminated. Most compressor and engine manufacturers offer them as standard equipment on large machines and options for smaller frame sizes.

Final Words

The crankcase explosion relief valve (ERV) rapidly relieves excess pressure, prevents flame, and rapidly closes after the crankcase pressure is relieved.

More to Read

1. Renewable energy
2. Nuclear energy

Flow control valve

Why is a bypass line required for the control valve?

A bypass line may or may not be required during installing of a control valve in the piping of a process plant. Unless otherwise required, the necessity of installing a bypass line is determined by the P & ID creator (process engineer) in consideration of safety, operability, maintainability, economy, etc. Also, the process licensors and customers may be determined by the above requirements.

Therefore, in this article, I shall explain when a bypass line is necessary and whether it needs to be installed. In addition, we will also explain the points to keep in mind when installing a bypass line. By clearly stating the criteria for the necessity of bypass lines in a book that summarizes the concept and further describing it in the P & ID legend sheet (lead sheet), the process design department and the piping design department have a common understanding and are surely reflected in the design.

When installing a bypass line is required?

Bypass lines are often required at the control valve during plant operation. In a large process plant, it takes time to start up or shut down the entire process. Before the regular operation time, the production volume of the product (fluids such as steam or gas) needs to escape from the prime mover. So, installing a bypass line to the control valve can continue the operation.

Supplement: As for the pressure-equalizing line and pressure-equalizing valve installed around the high differential pressure control valve, the purpose of the installation is different from the above, so the consideration explained in this article is not necessary. In such a case, when performing maintenance of the control valve, close the block valves before and after the control valve, remove the control valve, and manually adjust the opening of the bypass valve to adjust the flow rate and control the operation of the plant.

When is a bypass line not required to install?

Depending on the fluid to be handled and the operating concept of the entire plant, troubles (leakage, erroneous operation, etc.) caused by installing a bypass line may not be tolerated. In such cases, the bypass line will not be installed even if the control valve has to shut down the plant for maintenance. In addition, from the viewpoint of the economy, there are cases where a bypass line is not installed to reduce the amount of piping work and the construction cost.

The above is decided by comprehensively considering operability and maintainability, construction cost, and operating cost, so it is necessary to consult with customers and related departments in good consultation. If a bypass line is not installed, an operation handle (hand-wheel) may be provided on the control valve as shown above to enable manual operation on-site if necessary. However, when selecting a control valve, consider whether the operation case at the low opening and high opening during unsteady operation is covered without bypass (whether the control valve is of the type with such rangeability).

In addition, as shown in the above figure, the control valve, including the cutoff circuit, often does not have a bypass line. We are considering the risk that dangerous fluid will flow out of the bypass line even though the broken circuit is working due to the opening due to the erroneous operation of the bypass line.

Points to be considered during installation of a bypass line

The flow coefficient (Cv) value
– of bypass valve ・ Countermeasures against the erroneous operation
– of bypass valve ・Operability of the bypass valve

Value of Bypass valve flow coefficient (Cv)
Since it is necessary to adjust the opening of the manual valve of the bypass line, the globe valve is basically selected. In principle, the same Cv value as the control valve is selected. However, depending on the operating case, it is necessary to select a valve that covers the low opening range and high opening range as necessary. The Cv is a universal capacity index and is simply defined in terms of U.S. gallons of water per minute at 60°F (or 15℃) that will flow through a valve with a pressure drop of 1 psi (or 6894.76 N/m2).

Countermeasures against the erroneous operation of the bypass valve

If the bypass valve is inadvertently opened by operation during operation, there is a risk that the operation will be disturbed, leading to plant failure or emergency stop. It needs to be designed properly. For example, removing the manual handle of the bypass valve during plant operation and using the Locked Open / Close specification are effective measures to prevent erroneous operations. It is also important to keep in mind the effect of opening the bypass valve by mistake and letting it flow back through the valve. If backflow is unacceptable, installing a shut-off valve on the upstream side is necessary.

Bypass valve operability

It is also necessary to think about the field indicators (pressure gauge, thermometer) necessity for operating the bypass valve should be installed in a place that can be seen from the operating position. For that purpose, it is necessary to consider the on-site target indicator by noting “In View” on the P & ID and clearly stating the relationship with the target bypass valve. It is also important to secure a space between the actuator and accessories and the bypass line, considering the maintainability and operability of the control valve.


In this article, I explained the idea of ​​the necessity of the control valve bypass line. Here is the summary of the article-
A bypass line may or may not be installed when installing a control valve in piping. Unless otherwise required, the necessity of installing a bypass line is determined by the P & ID creator (process engineer) in consideration of safety, operability, maintainability, economy, etc. Also, the process licensors and customers may determine the above requirements. By clearly stating the criteria for the necessity of bypass lines in a book that summarizes the concept and further describing it in the P & ID legend sheet (lead sheet), the process design department and the piping design department have a common understanding and are surely reflected in the design.

More to Read