Principle of Operation


As everything Bamford & Morris manufacture is custom designed individual applications need to be assessed on a case by case basis for suitability. However the following information should provide some further understanding of the theory behind how our Eductors, Ejectors, Heaters and Desuperheaters work and operate.



How they work - Eductors for Liquids, Solids, Slurries & Gases


How an eductor works. The basic principles of operation for a Bamford & Morris eductor for liquid, solids, slurry or gases.
Eductor - Principle of Operation

Eductors operate by using the pressure energy found within a high pressure motive liquid to pump, entrain or compress a secondary low pressure fluid. How an Eductor works is relatively straight forward and can be summarised as follows:

  • The high pressure motive fluid (P1) is passed through a specially shaped nozzle (orifice) which increases the fluid velocity and decreases the fluid pressure. By passing the motive fluid through a nozzle the static pressure energy within the fluid is converted into kinetic energy which increases the fluid velocity and decreases the static pressure.

This is process is known as the venturi effect.

  • As the high velocity stream exits the motive nozzle (orifice), at the point of maximum velocity, the vena contracta, an area of low pressure is generated. This low pressure area is equal to or less than the secondary low pressure fluid (P2), the suction fluid, so allowing it to enter the eductor body.

  • As the two fluids collide energy is transferred and the suction fluid is entrained into the motive fluid. The two fluid streams are passed through the parallel throat section where further mixing and energy transference occurs.

  • This fluid mixture is then passed through the diffuser section which by gradually increasing in diameter reduces the fluid velocity and so converts some of the kinetic energy back into static pressure energy and pressure recovery occurs (P3).

Eductors are generally inefficient devices, recovering up to approximately a maximum of 40% of the pressure drop between the motive and suction inlets, but their simplicity, lack of moving parts and other advantages over alternate technologies makes them the ideal solution for many applications.



How they work - Steam, Gas, Air & Vacuum Ejectors & Thermocompressors

How an ejector works. The basic principles of operation for a Bamford & Morris Steam, Gas, Air or Vacuum Eejctor & Thermocompressor
Ejector Principle of Operation

Ejectors operate by using gaseous fluids, such as steam or air as the high pressure motive fluid to create vacuums as well as to pump, compress and boost secondary low pressure gases. How an ejector works is again based on the venturi principle and is relatively straight forward as follows:

  • The high pressure motive fluid is passed through the ejector's motive nozzle which accelerates the fluid up to sonic velocities where 'choke flow' occurs. This increase in velocity causes adiabatic expansion of the motive gas from the motive pressure to the design suction pressure.

  • As the high velocity motive fluid exits the motive nozzle (V1) it draws in and entrains the suction fluid where an impulse transfer of energy occurs between the two fluids. The throat section of the ejector is designed for a specific suction load at the required discharge pressure. This is achieved by designing the throat diameter so that as the two fluids mix they are travelling at sonic velocities (V2) and therefore at 'choked flow' conditions.

An Ejector therefore is designed on the two choke flow principle.

  • As with the Eductor the diffuser section gradually increases in diameter and allows pressure recovery to occur. Depending on the pressures and flow rates, compression ratio's of up to 10:1 between the suction and discharge are possible in a single ejector. If greater suction pressures are required multiple ejectors can be installed in series.

  • Steam ejectors and thermocompressors, or ejectors which handle other condensable gases, will require an intercondensor between each ejector stage to 'knock out' the condensable fluids. This allows smaller ejectors to be used and minimises the motive requirements at each stage. Ejectors which are handling non condensable gases therefore tend to be larger and require a greater motive pressure and flowrate as the suction load progressively increases from stage to stage.

Applications include evacuating vessels, creating process vacuums, priming systems and recovery of waste gases / steam as well as dilute phase pneumatic conveyance. of solids.



How they work -  Instantaneous / Inline Steam Heaters 



How an instantaneous steam heater works. The basic principles of operation for a Bamford & Morris instantaneous, silent, inline steam heater.
Heater Principles of Operation


How a steam injection heater works is very simple and the principle of operation is very much as the name implies.

  • By using the venturi principle we can reduce the pressure of any liquid which has Newtonian behaviour, water for example, to below that of any available heating steam.

  • This drop in pressure allows the heating steam to enter the Injection Heater and mix with the liquid. A specially designed throat section ensures a high level of turbulence and promotes rapid and homogeneous mixing of the steam with the liquid.

  • The steam transfers its energy, heat, to the liquid and condenses as it cools so that it exits the Injection Heater as a single phase, higher temperature liquid.

As with an Eductor the liquid passes through a diffuser section which reduces the fluid velocity and allows some pressure recovery back up to or near the initial pipeline pressure.



How they work -  Spray Type Desuperheaters 



How a Spray Type Desuperheater works. The basic principles of operation for a Bamford & Morris desuperheater.
Desuperheater Principles of Operation


  • The spray type desuperheater is used to reduce the temperature of superheated steam to near saturation temperatures (+ 3 degC) .

  • Cooling is achieved by evaporation of a cooling medium upon contact with the steam flow. The cooling medium is sprayed into the steam flow in the form of fine droplets to increase fluid surface area and therefore fluid / steam interaction.

  • The cooling fluid must be at a pressure of at least 1 bar greater than the superheated steam flow and, dependent on the required reduction in superheated steam temperature, pressure drops across the desuperheater range from 0.1 to 1 bar.

  • Having a fixed geometry spray type desuperheaters require a relatively stable range of operation having a maximum turn down of 2:1.