The design basics of a vacuum conveying system

When you are designing a vacuum conveying system, there are a number of questions you need to ask to get the system specification right. You will also want to make sure that you have procedures and processes in place, as well as emergency materials such as metal bonding adhesive from companies such as should your system have a leak or breakage.  Let’s look at five of the most fundamental points.

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1. What is the bulk density of the material?

Bulk density defines how many cubic feet per minute of air must be moved to get the material to travel along the conveying line. Weight is not always a reliable guide; for example, very fine powders may be light but can sometimes require extra filters and larger vacuum pumps.

2. How far do you want to move it?

The further you need the material to move, the bigger your vacuum pump needs to be. Right angle turns in the tubing are equivalent to adding six or seven extra meters to the distance.

3. How quickly does it need to be moved?

Most pneumatic conveyors move material and then discharge it. If this needs to be done in batches because different materials need to be moved at different times, the system will need to be able to cope with the highest speed required at any point in the batch – even though the main conveying job is carried out at lower rates.

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4. How will the material behave?

If the materials are blended, they can separate while they are being moved, with dense phase conveying often used to prevent this from happening. When powders are not free-flowing, the vacuum receiver is often customized to provide a full opening discharge valve to ensure quick refills of a feeder.

In safety terms, if the dust from the material being conveyed is combustible, a vacuum conveyor is the safest choice. This is because when the system leaks, it leaks ‘inwards’ and a leak does not result in a flammable dust cloud in the plant.

5. How will the material enter the conveyor?

The pickup point can be the most troublesome element of the entire system. It is sometimes difficult to get materials into the conveyor tube, even though they are conveyed without trouble once inside the Vacuum Conveyor.

Sticky materials, for example, maybe difficult to get into the tube through automatic feeds. Sometimes vibration is used to stop the materials sticking in the pick-up bins.

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