What are the reasons for blocked conveying lines?

All pneumatic conveying systems block sometimes.  Clearing a pipeline means downtime, loss of production and can be a maintenance headache so ensuring your system runs as smoothly as possible day after day is critical. Here at Mactenn we have been designing pneumatic conveying systems for years using our knowledge and experience to design systems that aim to provide the most reliable and maintenance free systems possible.  We do not like blockages or any other maintenance issues any more than you do but if they do happen, understanding where to look to minimize downtime is essential.  Here are some pointers for a quick recovery:

1.     Machine Settings – Settings of the system should remain as set during start-up. However in practice they are often modified intentionally or unintentionally during maintenance or in order to overcome an upset condition. Incorrect settings can create material blockages.

2.     Changes to controls – Sometimes it is essential to modify PLC programming. For instance, adding additional distribution valves, changing the requirements of the weighing system, changing the number of and/or weight of ingredients for a mixer charging system.  Any control changes should be carried out in conjunction with the system manufacturer.  If not, the customer may inadvertently change some of the basic settings, times etc. fundamental to the operation of the pneumatic conveying system.

3.     Out-of-Specification Material – Has your material changed? Is the bulk density, particle size distribution and flowability what the system was designed for? If the answer is no, the blockages could be explained by the material.  

4.     Foreign Material – Sometimes foreign objects such as used welding rods, cigarette packs, wire, nuts and bolts, etc. find their way into the silo/feed hopper etc.  As these materials accumulate they create a blockage preventing the conveyed material from entering the conveying line or moving along down the pipeline.

5.     Moisture in the conveying process - Moisture can change the material characteristics. Materials will become sticky or poorly flowing resulting in conveying blockages. For instance, with baghouse and ESP installations there is the possibility that water or steam may enter the hoppers e.g.,  due to a faulty boiler tube/s.  As most types of ash are hygroscopic (they absorb moisture from their surroundings) moisture will change the consistency of the ash and create conveying difficulties.

6.     Air Supply Problems - If the air supply to the conveying system has inadequate pressure, flow and/or contains too much moisture, this can cause the material to slow down in the pipe line. Usually this causes the pressure to rise and if the air supply pressure cannot be maintained through the cycle, the system will block

7.     Pipe Line Incorrectly Installed – Any changes to the original pipe route configuration can cause blockages. If you have a need to modify a pipe route contact the supplier for verification or for re-configuration and resizing of your system.

            8.  Recieving Bin High Level Probe Failure- Check the operation of the level probes if fitted. Level probes are installed to       signal the system that the receiving bin is full (i.e. when the probe is contacted by material) and to shut the system down until the probe is uncovered. Faulty level probes may allow the system to keep on conveying material to the bin/silo and over fill it. If not noticed by the operating personel, the sytem will continue to convey, gradually filling the pipeline until it blocks.

            9. Defective Components- Faulty components such as pressure regulators, solenoid valves, etc., can result in failure of the conveying air supply leading to pipeline blockages.




The good news is that most problems can be solved by a simple phone call to our Service Department and it is free.  


To find out more please contact us at Mactenn


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