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Thursday, April 20, 2017

Clean air is crucial for the pneumatic conveying of solids in the food and packaging industry. It removes moisture and contaminants that ensure the system does not experience premature wear or damage. It further guarantees your company will experience none of the following:
  • Potentially harm your consumer
  • Diminish your product quality
  • Render your product entirely unfit for use
  • Lead to your product being recalled
  • Cause legal action against your company due to complaints
But what are the major contaminants of pneumatic conveying lines?

Sources of contamination in the pneumatic conveying of solids in the food and packaging industry

If you think that oil is the major contaminant of a pneumatic conveying line, then you better think again. Maintenance Technology has revealed that only a minute portion belongs to oil and close to 99.9% of the liquid contamination entering your compressed air systems actually comes from water.

Imagine a 100 cfm compressor and a refrigeration dryer combination working simultaneously and operating 4,000 hours. This can produce approximately 2,200 gallons of liquid condensate per year. Thus, the need for a well maintained air dryer that could efficiently remove water and adjust humidity levels.

Pneumatic conveying of solids and the the amount of water it produces
Read more about air dryers

Many suppose that oil is not used in pneumatic conveying? But is this truly the case?
A small percentage of oil is still used in the compression stage for sealing, lubrication and cooling. This is necessary for the efficient functioning of your air compressor. However, as oil enters the compressed air system and gets mixed with vapour, it creates the damage.

Note however, that less than 0.01% of the overall volume of the oil and water mixture is accounted to oil. Thus, the main culprit of contamination remains to be water.

Air quality

Air compressors are the heart of any pneumatic system. However, this also draws in large amounts of air from the surrounding atmosphere which contains many airborne contaminants such as:

Pneumatic conveying of solids and air quality contaminants

Atmospheric dirt

In a typical industrial environment, approximately 140 to 150 million particles of dirt lurk in every cubic yard of air. What's even more amazing is that compressor intake filters fail to capture 80% of these particles because it is simply too small. As a result, atmospheric dirt can enter your food and packaging processing line.


Micro-organisms such as bacteria and virus come into your compressed air system via the warm and moist air that enters into it. Thus in an ambient air food and packaging plant, it is most possible to find as much as 3,850 micro-organisms per cubic yard within its premise.

Oil vapor

Air contains oil in the form of unburned hydrocarbons drawn into the compressor intake and from the compression stage of a lubricated compressor. Once these vapours cool and condense, it can cause contamination issues such as liquid oil.


Air temperature increases during compression; this allows the air to easily retain incoming moisture. However, amounts of water without proper protection can now start entering your system which can harm your operation and product output.

Air compressor operations and the pneumatic conveying of solids

The regular operation of your food and packaging plant causes your air compressor system to deteriorate. Evidence of this is the existence of rust and pipe scales in your pneumatic pipelines brought about by the coolants and lubricants.

Unless properly attended and eliminated, this can result in various damages and blockages to the system which can extend to the contamination of your final product and processes.

Air storage devices and the pneumatic conveying of solids

Air is cooled to a usable temperature after the compression stage in a system to reduce the ability of the air to retain water vapour. During this process, a portion of the water vapour is condensed into liquid water while the remainder of the air is continuously cooled by the air receiver, piping and expansion of air in the:
  • Cylinders
  • Machinery
  • Tools
  • Valves
However, condensed water and water aerosols can cause corrosion to the distribution and storage system; thus damaging the production machinery and the end product itself.

Further damages associated with it include reduced production efficiency and increased maintenance costs due to the washing away of the pre-lubricants on valves and cylinders.

How to mechanically clean systems for the efficient pneumatic conveying of solids

Now that we are aware of the many contaminants that may get into your system, here are some tips on how to mechanically clean it.

Removal and manual cleaning

This is applicable for very short conveying lines with a few manageable pieces. However for systems with long pneumatic conveying lines, the other options listed below may be a better option.

Challenge: It can only be used in short conveying lines.

Scouring material

To remove contamination, the following materials are used to scour the inside surface of the pneumatic pipes:
  • Corn
  • Rice hulls
  • Salt
Challenge: It fails to cover all the surfaces as it follows the same concentrated air path the regular materials go through.


In this process, a surface-contacting projectile is inserted into the conveying line multiple times to remove surface contamination. This video demonstrates how it works.

Challenge: Choosing a reliable pipe cleaning company that has efficient pigging apparatus.

Spray washing or Cleaning-in-Place (CIP)

Cleaning-in-place (CIP) or spray washing requires a cleaning solution or a sprayer which is sent through the conveying line.

Challenge: The complete removal and drying of the conveying line before it can be used again

Dry ice conveying

In this process, dry ice is used rather than scouring materials. It aims to cryogenically freeze the pipeline deposits to make it brittle. It also changes the pipe dimensions and causes it to shrink.

Challenge: Its ability to interact with the entire inside pipe's surface remains questionable.

Sanitation options for your pneumatic conveying of solids in the food and packaging industry

Mechanical cleaning may work for some industries but for the food and packaging industry it requires more stringent measures. They are required by law to instigate written food safety management systems (FSMS) upon the principles of the Hazard Analysis Critical Control Point (HACC). Most of the time, this also includes adhering to international standards such as ISO22000:2005, which fully endorses the principles of the HACCP system.

HACCP and the pneumatic conveying of solids

What is required by HACCP standards?

HACCP standards require a hazard analysis including the type of process and facilities used. All of these have to be assessed and identified to ensure sufficient and efficient cleaning and sanitation processes are done to ensure the removal of all biological contaminants.

Pneumatic conveying of solids and hygiene legislation

Some of the current sanitation options that validate the process does indeed kill biological contaminants include the following:

Spraying antiseptic foam

Spray washing doesn't guarantee that you will get rid of micro organisms, but with antiseptic foam pumped down into the conveying line, you can ensure it will eliminate these unwanted micro organisms. However, validation is still required to ensure the surface coverage and the needed residence time for the foaming agent.

Applying heat to the piping system

Another sanitation option for pneumatic systems is to elevate the temperature of pipe surfaces to kill contaminants. This is done through heat tracing or by pumping hot air through the system. The only validation requirement is the heating process, the degree and the duration of the process.

Adding Gas

You also have the option to add antiseptic gas such as chlorine dioxide or ozone into the air stream to kill the micro organisms. However, the gas concentration inside the pipe and its duration has to be validated to guarantee the micro organisms are killed.

Well-maintained pneumatic conveying lines for better production efficiency

Food processing plants should ensure that air quality is treated prior to it entering your distribution system. Maintenance programs should be tailored according to the following factors:
  • Construction material of air dryers (i.e., steel or copper)
  • Filtration capability
  • Flow capacity (system size)
  • Safe working pressures
  • Size of connecting lines
  • Type of compressed air system
  • Water capacity
Regular evaluation of these factors should also be done to check the efficiency of the compressed air system's operation including the maintenance of air dryers and purification components.

Do you need help designing and planning pneumatic conveying systems for solids in the food and packaging industry? We are happy to help. Contact us today.

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Are you involved in handling bulk powders, granules, pellets or flakes? If so, you should consider going to the Australian Bulk Handling Expo. Come see us exhibiting at BULK2022 EXPO from 24th to 26th August 2022 at Melbourne Convention Center. Read on for more information.

Are you involved in handling bulk powders, granules, pellets or flakes?
If so, you should consider going to
the Australian Bulk Handling Expo.

Come see us exhibiting at BULK2022 EXPO from 24th to 26th August 2022 at Melbourne Convention Center. Read on for more information. Find out more.