Pneumatic conveying and food safety

13 November 201814 min reading

“Pneumatic conveying represents an important topic in engineering and is encountered in a variety of industrial processes. Widely used in flour industry to handle and transport dry and free-flowing powdered and granular material because it is suitable for variety processes. Fine particles of lees 1 micron, as well as 15 mm rocks, can be conveyed vertically and/or horizontally from distances of few meters to a few kilometers at rates of hundreds of tons per hour requires less control and maintenance, and it is cleaner easier to automate. Great progress bulk transport improves the hygiene of production systems totally enclosed, and dust generation is minimized.”


Mulugeta Zewdu

Independent Researcher

Main purpose to present multiple sources of studies to explore what exist behind scenes and realize scope activities of flour milling industry and bulk transportation addresses a lots of verification and validation facts of safety quality assurance. Food and Drug Administration FDA “Current Good Manufacturing Practices and Hazard Analysis and Risk-Based Preventative Control for Human Food”.

The Flour Milling industry is considered a low-risk area within the food handling enterprises since the flour is mainly used for baking purposes. However, there are pathogens that produce toxins that can be heat stable and can cause illness even after the product has been baked such as Bacillus and Staphylococcus species.

Protection from Adulernts Protection of food, food handling & transportation, and food direct contact surfaces from various microbiological, chemical and physical contaminants, such as employees lubricants, fuel, pesticide, cleaning compounds, sanitizing agents, floor splash, aerosol, mist etc. Flour can be considered ‘adulterated’ if they become contaminated by such substances.

Any flour product, component and/or ingredient is deemed to be adulterated if it meets the definition of an adulterated food under Section 402 of the Food Drug and Cosmetic Act and its related regulations under 21 CFR. clean & sanitary practices of Flour handling & transportation because the adulterant ‘may’ be present due to improper sanitary practices. Foods processed in unsanitary conditions-these [handling, transportation, packaging materials] direct contact surfaces can be considered adulterated even without any evidence or measures of a contaminant.

If it food has been prepared, packed, or held under insanitary conditions whereby it may have become contaminated with filth, or whereby it may have been rendered injurious to health

Protection from adulteration can be a 3-step process - before, during and after processing best-accomplished practices: After processing finally, the processor cannot be responsible for all possible sources and causes of adulteration after the product leaves the processing operation, but prior considerations could influence product adulteration after processing. Selection of packaging materials, packaging integrity, cleanliness of transportation trucks, and further handling instructions can prevent potential contamination from these: biological, microbial, pests, and chemical, adulteration by persons and conditions used in distribution, transport, storage, etc.

The effort to produce a safe and wholesome food product, SSOP, Pre-requisite programs essential implement during these three periods to assurance critical areas are covered and to prevent what could lead to a complicated (HACCP) system with much critical control points before implement ISO 22000, HACCP systems, ISO 22005. Nevertheless all those invested hygiene schemes useless, entail know-how latest pneumatic convey technology transportation uses in flour industry sector.

Many factors can play in transporting different food products. The bulk food transports dry or liquid products can be shipped via trailer or rail car. There are special categories of food that should be closely evaluated and may require additional measures to ensure product safety. This includes liquid egg, juice, and dairy. Dry products may consist of flour, sugar, salt, starch etc.

What is Pneumatic Conveying dry bulk handle and transport? In many industrial processes where raw material are required in bulk, pressure discharge truck used to transport them from the supplier’s warehouse or mine to the processing plant or final destination. As the implies, pressure discharge trucks unload their contents by means of a pneumatic conveying system and transport it through a pipeline into storage silo and hence, it is less expensive overall when large quantities of materials are being transported in bulk on a regular basis.

Pneumatic conveying represents an important topic in engineering and is encountered in a variety of industrial processes, chemical, pharmaceutical, food, glass, cement, plastics, mining, ports etc.

Widely used in flour industry to handle and transport dry and free-flowing powdered and granular material because it is suitable for variety processes. Fine particles of lees 1 micron, as well as 15 mm rocks, can be conveyed vertically and/or horizontally from distances of few meters to a few kilometers at rates of hundreds of tons per hour requires less control and maintenance, and it is cleaner easier to automate. Great progress bulk transport improves the hygiene of production systems totally enclosed, and dust generation is minimized.

Settling chambers, bag filter, reverse-jet filters and Hepa absolute filters, depending mainly material characteristics, while the conveying gas is usually air at ambient conditions, other gases may be used such as nitrogen and carbon dioxide in applications where there exists a risk of explosion or health and hazards.

Flow problems PD trucks represent a unique class of pneumatic conveying systems because of the mobile nature of the “feed system.” Self-unloading truck arrives with own blower and operator and connects to a fixed system at the plant.

More air flow leads to faster transfer rates in system constrained by an upper-pressure limit and fixed piping, this logic often leads to less efficient conveying and problems handling such as: excessive particle attrition friable material build-up inside, arching aerated bin bottom.

Great progress bulk transport improves the hygiene of production good storage and transportation required accuracy & reliable dosing ingredients is an essential part of ensuring production efficiency obtaining a homogeneous consistency test with good properties.

If the properties of the test do not correspond to the required parameters, it is usually difficult to provide appropriate subsequent processing to obtain cookies of the desired quality. The require to indicate special attentio in transport the ingredient, and development of equipment a well-known tanker and railway wagons with lifting capacity from 5 to 100 tons, for the transportation of raw material in powdered and liquid some technical aspect of bulk transport systems are diverse, the following information should be sufficient understand the general principles. In addition, the technical issues devoted the wheat flour ingredient.

Flour is normally supplied in bulk PD trucks and rail cars. Of these, flex it is fed into the bankers with air (from the installation on the tank or the Blowers companies). To unload 20 - 30 tons usually requires 20 - 30 minutes.

Pneumatic transportation of flour usually a large air flow and to avoid significant drying of flour should pay attention to its temperature and humidity. The analyses of sensitivity on weights show that the ranking robust with either cereals and grains or dried protein products always being in the top position. Wheat flour & Corn Flour ranking the highest grains Moisture content.

Why is it important to know the Grains Moisture content? Determining moisture content is an essential first step in analyzing Wheat or Flour Quality since this data is used for other tests.

Flour millers adjust the moisture in wheat to a standard level before milling. Moisture content 14% is commonly used as a conversion factor for other tests in which the result are affected by moisture content.

Moisture is also an indicator of grain storability. Wheat or Flour with high moisture content over 14.5% attracts mold, bacteria, and insects, all of which cause deterioration during storage and transportation. Wheat or Flour with low moisture content is more stable during storage.

Moisture content can be an indicator of profitability in milling. Flour is sold by weight, grain is bought by weight, and water is added to reach the standard moisture level before milling. The more water added, the more weight and profitability gained from the wheat.

Wheat with too low moisture, however, may require special handling & processes equipment before milling to reach the standard moisture level and special vehicle for bulk transportation.

In-Line Filter Remove Contaminations From Pneumatic Trailer Air Supply Contamination of product is one of the biggest concerns for carriers that use pneumatic trailers to haul food, plastics, or other high-purity commodities. Microscopic particles carried by the conveying air can cause major contamination problems.

Extremely fine airborne pollutants can elude an air intake filter. Material from the air intake filter and lubricating oil from a blower can enter the conveying air. All of these can result in product loss, silo cleanup costs, and downtime. Moving air transports dry, free-flowing granular materials within conveying line. The basic types of pneumatic conveying are dense and dilute phase.

Dilute phase pneumatic conveying is the method most commonly used in the general process industry and on dry bulk trailers. Dilute phase conveying uses a relatively low pressure (less than 18 psi) and high air velocity (1000 cfm). The conveying material occupies less than 40% of the cross-sectional area of the conveying line. Bulk conveying equipment includes a vacuum and dense-or dilute pneumatic conveying. A bulk trailer equipped with a motor-driven blower acts as a self-contained pneumatic conveying system.The type of air mover is determined by the flow rate and pressure.The environments of dry bulk trailer are extremely diverse and can contribute to contamination of plastics or food grade products. Dust concentration, particle size distribution, and the chemical composition of particulates are affected local factors and environmental conditions. Ambient particulates are a mixture of particles from natural processes and anthropogenic sources.

Pollutant concentration, size, and Chemical composition. All depend on the location of the dry bulk trailer, the industrial activities in the surrounding area, and weather conditions. For example, air contaminants may contain a high percentage of soot particles in areas with diesel engines.

However, the primary sources of particles (direct emission) are windblown, metal shavings from the blower, industrial processes, motor vehicle emissions, and fuel combustion.Coal and oil combustion contribute to most particulate emissions in industrial areas.Coal combustion particles consist primarily of carbon, silica, alumina, and iron oxide.Particles generated during oil combustion consist of carbon, cadmium, copper, cobalt, and nickel. Secondary particles are formed by the atmospheric transformation of gases to particles. Sulfur-derived particulates are a major component of secondary particles. Most of the atmospheric aerosol is distributed in a fine mode of 0.1-1.0 microns and a coarse mode, which is greater than five microns. These two modes generally have different physical and chemical characteristics and are produced by different sources.Combustion particles, including motor vehicle emissions, typically are fine mode.

Particles generated by crushing, grinding, loading and similar processes usually are larger than 15 microns. Particles ranging from 1-10 microns are suspended in air for appreciable periods by air currents and are not captured by an intake filter.An intake filter generally houses either a polyester or paper filter medium, which captured contaminants 10 microns and larger.

The filter is positioned before the positive displacement (P/D) blower and protects it from airborne. Particles larger than 10 microns settle fairly quickly and can be found only in near their sources or under strong wind conditions. These particles typically will be captured by the intake filter.

In addition to airborne particulate matter, the P/D blower can be a source of contaminants. Wear and corrosion of a blower can cause particulate generation. Age and lob wear, improper use and cool down, high temperature, moisture, and corrosive gases can promote corrosion and other undesirable chemical reactions, such as scaling. Another source of contamination is the oil released during a catastrophic blower failure. Oil from a blower injected into the conveying line contaminates the product.

Which contaminants enter the blower of a pneumatic conveying system depend on the performance of the intake filter and the presence of an inline, high-pressure (24 psi rating) filter. An inline, high-pressure filter is mounted after the P/D blower and filter the pneumatic air before it mixes with the product.

By installing an inline, high-pressure filter, 99,998% of particulates four microns and larger, and any hot oil or oil mist are removed from the airstream, leaving the load virtually free of contaminations.

Conclusion material conveyed with a positive displacement blower can be contaminated in various ways. The intake filter allows small particles from ambient sources to pass into the conveyed material. In some cases, the filter element can break down and pass into the load.

In the event of a catastrophic failure, lubricating oil will be injected from the P/D blower into the conveyed material. Most importantly, the deterioration of blower components produces very small particles that pass undetected into the conveyed material. No current legal standard impose acceptable contamination concentrations and particle size limits in food applications at the silo-loading point. However, contamination standard are imposed by each manufacturer’s quality assurance (QA) program in compliance with Food and Drug Administration recommendations. Most plastics manufacturers impose a similar (QA) program and test product samples for contamination at the silo.

Rejection of food grade or plastic products that are contaminated with shavings of iron, lead, and other metals is expensive for the shipper, carrier, and customer. Also, consider the possibility of oil contamination resulting from the failure of a P/D blower. This result in wasted product and increased maintenance costs because the shipping container, pneumatic conveying air-lines for silo must be cleaned again before reuse.

An inline, high-pressure filter can provide additional protection by capturing contaminants four microns and larger, hot oil, and oil mist. Installed after the P/D blower and before the product pickup in a dilute-phase pressure system, the filter can ensure that product contacts the conveying air without becoming contaminated.

How to combat moisture-related flow problems by using desiccant dehumidifier? Moisture can cause your hygroscopic material to build upon silo walls or form lumps that block pneumatic conveying lines.

1- Silo storage. 2- Pneumatic Conveying. 3- Truck and Railcar unloading.

The material’s surface vapor pressure depends mainly on the chemical and physical structure and, to some degree, on the material’s temperature and moisture content. For each different material and air temperature, the equilibrium relationship between moisture content and relative humidity differs.

You can keep the air and material in equilibrium and prevent condensation in the silo by using a desiccant dehumidifier to condition the air entering the silo, which will control its temperature and relative humidity to your specified level. Installing a desiccant dehumidifier upstream from the system’s blower can help you combat these problems. The unit can condition the air to meet your material’s requirements.

The Grocery Manufacturers Association (GMA) formed a Salmonella Control Task Force to develop this guidance document for the control of Salmonella when manufacturing low-moisture foods.

Identified hazard & controlled, safety quality assurance intricacy depend on breadth, depth and precision work demand senior leader strategic concept processes big picture highlights the main element to quality assurance scope procedure captures these elements and adds more information for functional responsibilities, objectives, and methods to achieved need multiple tasks force integrate & collaborate i.e. R&D, hygiene-audit etc. Food chain vastly complicated activities cannot summarize, to aware scope activities criteria clear that preventive measures were the only way to produce safe food, and the discipline of food hygiene was born.

Salient Knowledge about Silent Biofilm Risks to Food Industries Documented biofilms have been almost entirely composed of bacteria and the types of bacterial biofilms particularly related to pathogens there are however very few published studies concerning yeast biofilms in food processing.

problems in food industry, Biofilm formation also causes problems in food-related systems, industrial water systems as the paper and packaging industry. Biofilm formation on food processing surfaces, dry bulk pressure discharge truck counting as food processing surface because the raw material ingredient it’s in direct contact with P/D-silo storage.

HACCP with Biofilm assessment in food plants will provide clearer information of contamination, and assist the development of biofilm-free processing systems in the food industry. In these guidelines ‘validation’ is defined as ‘the obtaining of evidence that the food hygiene control measure or measures selected to control a hazard in a food are capable of consistently controlling the hazard to the level specified by the performance objective’ thus validation of control measures requires that effectiveness is measured against an expected outcome (for example reduction of the level of Salmonella by 99.999%).

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