Here at STB Engineering, we are a specialist pneumatic conveying systems manufacturer with over 50 years’ experience in all types of powder conveying systems. We benefit from our own in-house design facility and test house in which to develop our systems. We aim to be the leading experts in conveying technology, implementing new and innovative solutions at the forefront of our field.
We were pioneers of the Dense Phase conveying system in the early 1970s before developing our Pulse Phase and Dilute Phase conveying technology. Our vacuum systems have proven particularly popular in the plastics and PVC industries and we have also developed expertise in supplying to other sectors such as the food, pharmaceutical, chemical and mineral industries. With our long history of experience and innovation, you can rest assured that our knowledge of powder conveying systems is second to none.
You can find out below about the unique qualities of each conveying system by watching the videos below and reading the individual pages. If you have a question about our conveying systems, a work proposition or would just like to say hello, please don’t hesitate to get in touch with us by filling out our contact form. We would be happy to respond to any query you may have and help you find the right system for your company.
For most products in powder, flake or granular form. Particles are fully suspended in the air stream. Positive pressure – blowing system, negative pressure – vacuum system.
Speed: 18 – 35 m/s
Pressure: Up to 1 bar
Vacuum: Up to 0.5 bar
Dilute phase pneumatic conveying, sometimes also referred to as lean phase or suspension flow, is a mode of conveying where the material is kept in suspension in the air stream of the pipeline it is being conveyed in. This mode of conveying can be in either in a positive pressure system (blowing system) or a negative pressure system (vacuum system). The air stream must maintain a velocity high enough to suspend the product particles throughout the length of the blowing system or vacuum system. The minimum value of the conveying line air velocity to suspend a particle in the air stream is known as the “Saltation Velocity” and can be easily determined and tested for through pneumatic conveying trials. If the air velocity falls below this value the particles will drop out of the air stream and have a tendency to settle in the bottom of the conveying pipe.
This type of blowing or vacuum system is the most common and elementary type of pneumatic conveying system used around the world today.
These type of systems comprise:
Dilute phase pneumatic conveying systems normally operate at positive or negative pressures up to 1.0 barg and have a low product to air ratio, which is usually up to a maximum of 15:1 with conveying velocities from 15 to 35m/s.
Designing such a system firstly requires specific product knowledge gained through conveying trial data and then requires a series of complex calculations to size the system to determine: the pipe diameter; conveying air volume; conveying line pressure; and size the blower / vacuum pump, feed device and filters for the given conveying line duty and configuration.
For any of the these types of dilute phase conveying systems, it is possible to have complex systems that can convey to any one of multiple delivery points through the use of diverter valves or collect product from multiple collection points. It is also possible to design the systems in a form of a closed loop conveying system limiting the introduction of atmospheric air and providing containment, or introduction of dried air for hygroscopic products, or, an inert conveying gas such as Nitrogen where there is an explosion risk.
For most products in powder, flake or granular form. Particles are partially suspended in the air stream with a bed of moving material.
Speed: 8 – 18 m/s
Pressure: Up to 1 bar
Vacuum: Up to 0.5 bar
In a process where the amount of air circulated through its volume and velocity is decreased, allowing for an influx of product in its place, medium phase conveying is an often integral part of the pneumatic conveying system’s functioning.
As the stream of particles pass through the line and the conveying air velocity is reduced, the particles reach a point of saltation velocity whereby they start dropping out of the air stream and start to form a bed of material that’s ever-moving along the bottom of the pipe.
For a “medium phase system” – the air velocity itself is expertly controlled by an intelligent speed control and monitoring system, which controls the blower output, monitors the pressure and air velocity and ensures that the particles travel just above the suspension point.
STB Engineering have been providing specialist pneumatic conveying technology since its founding in 1969, becoming the UK’s leader in Bulk Material Handling and Pneumatic Conveying.
For cohesive powders. Plugs of material fill the entire cross section of pipe, an air knife injection system breaks up the plugs and reduces the risk of complete pipe plugging.
Speed: 4 – 10 m/s
Pressure: Up to 4 bar
The pulse pump was developed as an efficient solution to the problems of pneumatically conveying cohesive powders.
The pulse pump separates the product into discrete ‘plugs’ of powder and air in the pipeline. It does this by using an air knife system, enabling the product to be easily transported, with the product sliding through the pipeline rather than particles being fully suspended in the air stream. The pulse pump enables the following gains to be made:
For regular granular products. Product flows in a pulse or wave. The air stream is precisely controlled using an intelligent PLC monitoring system.
Speed: 4 – 15 m/s
Pressure: Up to 2 bar
Pulse Flow or Dune Flow conveying is used to convey regular granular products that need to be handled gently. Product flows in a pulse or wave over a moving bed of materials.
Pulse flow conveying is regulated through the use of an intelligent control system that monitors the flow path of the product, the conveying air velocity and pressure and the pulse flow condition, carefully regulating the system to maintain the correct and precise conveying condition.
Using pulse flow conveying, transfer rates up to 20 tonne/hr can be achieved and conveying velocities as low as 4m/s and as high as 15m/s thereby substantially reducing product damage and fines accumulation.
The pulse flow system offers many potential benefits, such as the ability to use smaller pipelines, low air consumption thereby reducing operating costs, reduced bend and pipe wear and attrition, as well as reducing product degradation.
For fluidisable powders and fine granules. Conveying with high product to gas ratio. Takes advantage of the fluidisation and air retention of certain materials.
Speed: 4 – 10 m/s
Pressure: Up to 4 bar
The dense phase vacuum conveying system pump is a batching system designed to pneumatically convey free-flowing powders in a fluidised state. The vessel is charged with product and fluidising air is introduced through a porous membrane. On opening the discharge valve, fluidised product enters the pipeline and is transported to the receiving vessel, with the product sliding through the pipeline rather than particles being fully suspended in the air stream. The dense phase conveying system design enables the following gains to be made:
Dense phase pneumatic conveying systems are designed to be a simple and effective method of transferring material from a single collection point to either a single or multiple reception points. It can be used to transfer difficult, abrasive or friable materials. The flow of material in dense phase conveying is not continuous, it is plug flow, the material moves in pockets.
The dense phase conveying system design is made specifically to reduce the amount of pipeline wear and it can be used to achieve the highest possible levels of productivity.
In dense phase conveying systems, due to the less amount of air being used, the conveying velocity is less when compared to lean (dilute) phase conveying. Also, the main difference between dense phase pneumatic conveying and dilute phase is that in the case of dense phase conveying the SOLID TO AIR RATIO is high.
