Up to three or four machines everyone starts the same way: a loader on top of each machine, bags beside it. As the number of machines grows, the staff carrying bags, the hoppers left open and the mixed-up materials start to grow too. In this article we explain the right time to move to central vacuum conveying and how the system is installed.
When to Move to a Central System?
There is no exact number of machines, but the following symptoms are signs of maturity:
- 4+ machines, each with its own loader/dryer to maintain
- Hours of every shift going on carrying bags and filling hoppers
- Material taking up moisture from open hoppers, mixed-up raw materials, contamination on the floor
- The need to supply more than one machine from the same dryer
What a central system gains you: raw material is stored at a single point (silo, octabin, big bag) · the closed pipeline cuts off contact with dust and moisture · staffing needs fall · gravimetric dosing and drying become centralized.
The Main Components of the System
A typical central conveying system consists of five layers:
1. Source: Silo, big bag station or octabin. Suction lances are used for drawing from octabins and drums — stainless, aluminum and angled types are available.
2. Vacuum generator and filter: The central pump station is the heart of the line; cyclone and filter units catch the dust in the conveying air.
3. Pipeline: The most neglected part of the system, yet the one that determines its life (in detail below).
4. Distribution: Material distributors (distribution table/station) determine which raw material goes to which machine. At the coupling table the line is connected to the target machine manually or automatically. Lines getting mixed up is prevented with color coding.
5. Machine-mounted receivers: On top of each machine a vacuum receiver draws material from the line according to the demand signal.
Pipeline: Details Matter
Granulate moves in the pipe at speeds of tens of km per hour and can wear both the pipe and itself:
- Pipe selection: Standard stainless pipes are sufficient for most applications; on lines carrying glass-fiber material, wear resistant pipes are essential
- Elbows: 90% of wear happens in the elbows. Wide-radius pipe elbows are used, with glass elbows (wear can be monitored by eye) at critical points
- Connections: Pipe couplings determine the sealing — in a vacuum system even the smallest amount of false air (Falschluft) reduces the conveying capacity
- Speed balance: Excessive speed produces wear and dust (angel hair); low speed causes line blockages. Pipe diameter and vacuum power must be calculated together
Metal Safety
A central system is also a motorway for metal particles to spread to every machine: a broken drill bit coming from a granulator threatens every screw the line feeds. Placing magnetic separators at critical points — a hopper magnet at the machine inlet, a bullet separator in the line — is negligible insurance compared with the cost of repairing a screw and barrel.
Critical Points During Installation
1. Leave room for expansion: Empty coupling positions on the distributor, a 30% margin in pump capacity 2. Line labeling and color coding from the very first day — it is very hard to correct later 3. Dryer integration: The line carrying dried material should be kept short; a long line re-moistens the material 4. Maintenance access: Filters and elbows must be reachable
If you would like a line diagram and component list drawn up for your plant, contact us — let's work out the pipe route and capacity calculation together based on your machine layout.