Different Process Equipment Available in an Industry

The standard set of instrument symbols and Process Equipment Symbols used to Develop P&ID.

In this article, we will see some process equipment symbols used in P&ID.

Identification of Pipe Line Number in P&ID

What are process equipment symbols?

These are a standard set of instrument symbols defined by ISA 5.1

These symbols are used for developing P&ID

ISA: International Society of Automation.

The main purpose of ISA standard is to advantage enough information enables everyone to read process flow diagram and to establish uniform means of instrumentation symbols used in measurement and control

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A complete list of the common set of instrument symbols used for developing P&ID and PFD is shown below.

Centrifugal and Positive Displacement Pumps

Centrifugal Pumps

A centrifugal pump is a mechanical rotating device designed to transfer or lift fluid from one point to another point using rotational energy through one or more driven rotors called impellers.

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Positive Displacement Pump

  • A positive displacement pump lifts the fluid by surrounding it in a fixed volume and moving it mechanically through the system.

  • The action of the pump is cyclic and can be driven by pistons, screws, gears, rollers, diaphragms, or vanes.

Centrifugal and Positive Displacement Compressors

  1. Centrifugal Compressors
  • Centrifugal compressors or turbo compressors are types of dynamic compressors, these compressors with radial design work at a constant rate or flow with constant pressure.

  • As gas is allowed to flow through the impeller, these centrifugal compressors elevate the gas pressure by adding some amount of kinetic energy velocity to the gas.

  • When the flow through the diffuser is reduced the static pressure or potential energy of a gas is increased by kinetic energy.

  • But some external conditions such as inlet temperature may affect the performance.

  1. Positive Displacement Compressors
  • In this positive displacement compressor through the intake, the air is sucked or drawn into a compression chamber.

  • The volume of the chamber is mechanically reduced through motion until a set pressure is reached.

  • The valve now discharges the compressed air through the valve at the rated pressure to provide airflow.

Heat Exchanger & Distillation Columns

Heat Exchangers

  • Heat exchangers are the most crucial element in every process plant.

  • It is a device that simplifies the process of heat exchange of fluids from one medium to another medium of different temperatures the fluids may begas, liquid, or a combination of both.

  • Heat exchangers regulate the overall efficiency and size of the system.

1. Spiral Heat Exchangers

These exchangers are circular units that contain two concentric spiral flow channels, one for cold fluid and the other for hot fluid.

2. Hairpin Exchanger

  • In this exchanger, the fluid temperature differences between the shell and tube sides are maximized.

  • These heat exchangers use true counter-current flow.

3. Double Pipe Heat Exchanger

  • These are heat exchanger devices that transfer or exchange heat between two fluids without mixing them.

  • These are basic heat exchangers with very flexible configurations.

4. Shell and Tube Heat Exchanger

  • This is another type of heat exchanger device that consists of several tubes placed inside a cylindrical shell,

  • These heat exchangers allow for a wide range of pressures and temperatures.

5. Re Boiler Heat Exchanger

  • A Reboiler is another type of heat exchanger device designed to generate the vapor supplied to the bottom tray of a distillation column.

  • The liquid from the bottom tray of a distillation column in the exchanger is vaporized partially, which is usually a shell-and-tube type.

6. Single-Pass Heat Exchangers

  • In single-pass heat exchangers, the fluids will flow only once between each other.

  • The child water is allowed on only one side of the tube and into the water box and finally leaves at the other end.

7 U Tube Heat Exchanger

U tube heat exchanger is a kind of heat exchanger named after the ‘U’ shape tube.

  • This is made by using components like the tube box, shell, and tube bundle.

  • These exchangers belong to petroleum and chemical equipment.

  • These exchangers can expand or contract freely.

  • These exchangers will not produce thermal stress due to the temperature difference between the tube and shell

  • These exchangers are most suitable for high temperatures and pressure.

Distillation Columns

  • Distillation is a process of separation of more than two fluids into their parts with desired purity through heat and mass transfer.

  • The degree of separation in the distillation process depends upon the relative volatility of the components that need to be separated.

  • In the distillation process, the vapor phase contains more volatile components that have lower boiling points.

  • On the other hand, the original mixture contains more volatile components that have a higher boiling point.

  • The vapor is now cooled and condensed at the overhead condenser

  1. Packed Tower
  • It is suitable for low-capacity operations.

  • The packed columns are generally used for smaller diameters of less than 600 mm and a minimum number of stages

  • These are best suited for handling foaming liquid.

  • In the packed column, the packing is used as a gas-liquid contacting device.

  • It is simple in construction.

  1. Plate Column
  • Plate columns are most suitable for higher flow rates of fluid.

  • The plate columns are generally used for relatively large diameters & a large number of stages

  • These are not appropriate for handling foaming liquid.

  • In a plate column, the plate is used as a gas-liquid-containing device.

  • It is complex in construction.

Cooling Tower

  • A cooling tower is a specialized heat exchanger where both air and water are brought in direct contact with each other to reduce the temperature of the water that is circulated throughout the tower.

  • During this period a minimum volume of water is evaporated.

  1. Induced Draft Cooling Towers
  • In these cooling towers, the fans are mounted on top of the unit.

  • The air is pushed against by blowers located at the base of the air inlet face on forced draft towers.

  1. Forced Draft Cooling Towers
  • The low-potential heat generated in the production process is removed by these cooling towers.

  • The hot water is combined with a counter flow of air that results in a heat transfer.

  • Forced draft cooling towers are most preferred in the paper and chemical industry.

  1. Hyperbolic Cooling Tower
  • This hyperbolic cooling tower is incorrectly known as a hyperboloid cooling tower.

  • Due to higher structural strength and minimum usage of material, these cooling towers are considered a standard design for natural draft cooling.

  • The hyperboloid shape also supports accelerating the upward convective airflow, and thus improves cooling efficiency.

  1. Natural Draft Cooling Tower
  • The natural draft cooling tower is the open type with a direct contact system.

  • These towers function along with a heat exchanger, the hot water from the system is cooled in direct contact with the atmosphere.

  • To increase surface area and optimize the cooling process hot water is sprayed through the nozzles.

Furnace and Boilers

  1. Furnace
  • A furnace is a structure or a combustion area of the boiler in which burning fuels produce heat in excess air supplied by draught systems.

  • In the furnace, the air is heated and distributed using ducts.

  1. Boilers

A boiler is a closed vessel in which water is heated to produce steam (a vaporized form of a liquid) under pressure.


A reactor is a vessel or stage for allowing more than two substances to react chemically with each other.

  1. Tubular Reactor

A tubular reactor is a tube where the rate of reaction progresses as the reactants move downwards the conduit.

Tubular reactors are continuous flow vessels.

These are used to mix different types of chemicals in a steady state.

The mixing of chemicals in a reactor depends on the function of reactants’ position and function of time to complete a chemical reaction.

  1. Hydro Cracking
  • A hydrocracking unit is also known as a hydrocracker.

  • It is a two-stage process for combining catalytic cracking and for hydrogenation.

  • This uses gas or oil, which is heavier and has a higher boiling range than distillate fuel oil.

  • In the presence of hydrogen and a catalyst, this hydrocracker will crack the heavy molecules into distillate and gasoline.

  1. Hydro Desulfurization
  • Hydrodesulfurization (HDS) is the process of removal of organo-sulfur compounds over heterogeneous catalysts during the refining of petroleum.

  • Noxious sulfur oxides are formed if sulfur is not removed during the process of hydrodesulfurization.

  • This may cause air pollution upon fuel combustion.