Conveyors’ lubrication in a SABMiller Brewery (images' credit: Tom Parker/OneRedEye/OneRedEye)

Conveyors' Lubrication 

in the Food and Beverage Bottling Line

The traditional and still main function of the lubricants is visible in the figure on right side: to keep a separation between the surfaces of other materials, preventing friction. With the time and the diversification of the industrial technologies, the amount of the functions has grown.  

Today, food-grade lubricants must perform the functions as any other lubricant, providing protection against:

  • wearing, 
  • friction, 
  • corrosion,
  • oxidation,
  • contamination, 
  • degradation by food, beverage, water or steam,

they have to dissipate heat, transfer power, being in the meantime compatible with rubber and other sealing materials, as well as provide a sealing effect in some cases.  

  The historic goal of the lubricants was the separation of other surfaces, to prevent friction and to decelerate surfaces’ wearing (credit Lubriplate Lubricants Co., 2014)

In addition, different applications within the Food, Drug and Beverages business demand that lubricants have to:

  • exhibit a neutral behavior toward plastics and elastomers, 
  • be able to dissolve sugars, 
  • comply with food, health and safety regulations, 
  • be physiologically inert, tasteless or odorless,
  • be internationally approved.

The last point is particularly relevant when considering that it conditions the international future saleability of the production of the Beverage Bottling Line.  Modern food-grade lubricants can be eated without to experience negative consequences. 

  The modern food-grade lubricants are chemically engineered with much more than lubricants.  They also include < 20 % detergents, anti-fungal agents, anti-bacterial substances, etc. (credit Lubriplate Lubricants Co., 2014)

Understanding viscosity

One of the most important features of the lubricants is its viscosity.  In layman words, the viscosity of a fluid is a measure of its resistance to gradual deformation by shear or tensile stress. For liquids, it corresponds to the informal notion of “thickness”.  Because of its definition, it is strictly related to the energetic level of the fluid, itself measured by its temperature.  Why ?   

From a deeper point of view, viscosity is related to shear stress and the rate of shear in a fluid, illustrating its dependence on the mean free path of the diffusing particles.  With reference to the video below, imagine to launch a billiard ball marked B in the middle of sixteen others, marked A1, A2, …, A15, A16 in movement on a circular table.  Balls experiencing unavoidable recoils after hitting the table borders or another ball.  Establish a statistics of the mean free paths of the ball B, after successive hits and recoils.  

After having increased the average speed of the sixteen billiard balls on the table, launch again the ball B test on the table.  Increased average speed means an increased kinematical energy of the balls A1, A2, …, A15, A16.   Compare the statistics of the mean free paths of the ball B and you’ll discover something relevant.  To different average kinematical energies are related to different values for the mean free paths.  

  Viscosity is related to shear stress and the rate of shear in a fluid, illustrating its dependence on the mean free path of the diffusing particles. The diffusing particles may be represented by sixteen blue colour balls. Compare the statistics of the mean free path of a test ball B launched between sixteen others in movement before at slow and later at high speed. We’ll discover that different average kinematical energies are related to different values for the test ball B mean free path

    Since years greasing is no more a necessarily manual activity. Perma automatic grease cartridge allow automatic lubricating systems. The cartridge visible above contains 120cc of grease and  is timed for a six month period.

Kinds of food-grade lubricants

The following is a list of the food-grade most commonly used lubricants, all of them used up to 177 ºC (350 F):

  • Aluminum Complex

Good high-temperature and water-resistant properties. Used in steel and paper mills. Most common food grade thickener with H1 approval. 

  • Polyurea

Excellent oxidative resistance because of non-metallic thickener. Grease of choice for electric motors and sealed-for-life applications. 

  • Organophilic Clay

Non-melt resulting in good high-temperature properties along with H1 approval for food grade. 

  • Calcium Complex

Good water resistance and H1 approval. 

  • Calcium Sulfonate

Very good inherent corrosion resistance and high EP along with H1 approval, but expensive because of high thickener content.  Used in corrosive and high-load environments. 

The table below shows the most proper range of ISO viscosity grades for different applications, commonly part of the Food and Beverage packaging Line. Generally, lower base oil viscosities (e.g. ISO 100 or less) are used in high speed applications and higher viscosity base oils are used for slower speed or heavily loaded applications.

Food-grade lubricants ISO and US Norms

   Relation between the ISO viscosity grade and the application (credit Lubriplate Lubricants Co., 2014)

Years ago the US Department of Agriculture (USDA) created the food-grade designations H1, H2 and H3.  The approval of a new lubricant and its registration in one of these categories depends on the list of the ingredients and is strictly related to the possibility of contact between lubricant and food or beverage:

  1. H1  in food-processing environments where there is the possibility of incidental food contact;
  2. H2  on equipment and machine parts in locations where there is no possibility of contact;
  3. H3  used to prevent rust on hooks, trolleys, etc. 

Deciding whether there is a possibility of contact is particularly difficult, implying to imagine a multiplicity of situations and configurations which are not associated to the common use of the Food and Beverage packaging Line.

The minimum requirements the prospected Vendor of lubricants has to comply, allowing food and beverage production international saleability (and, we’d like to add, Production Manager peace-of-mind), can be resumed in the following five points:

  • H-1 lubricants throughout the plant can significantly simplify the HACCP program by completely eliminating lubrication as a potential chemical hazard;
  • NSF H-1 registered, Food Machinery Grade;
  • manufactured in compliance with ISO 21469 guidelines;
  • formulated with ingredients that comply with FDA Regulations 21 CFR 178.3570, 21 CFR 178.3620, 21 CFR 172.878, 21 CFR 172.882 and 21 CFR 182 for lubricants with incidental food contact;
  • meeting USDA H-1 safety standards. 

  Would you run your own car knowing it has nearly no oil or that the grease to lubricate other mechanical organs terminated since months ?  Food and Beverage Packaging Lines are more restrictive than a car, when dealing with the critical subject of Conveyors’ lubrification (image credit Integrated Engineering, 2014)

How-much lubrication requires a Sampling Table ?

On Bottler’s side there is one very important requirement: 

                 to provide a separate lubrication to the Sampling Table.

Why “separate” ?  

 A rejection Table devoted to empty glass bottles' standstill rejection.  An application as critical as the Sampling of rows of full bottles, requesting similar amounts of lubricant.  What visible is a reference for the amount sufficient to assure correct sampling of 60000 bottles-per-hour (~17 bottles-per-second) on polished chains at a linear speed of ~1.3 m/s.  We are suggesting a separate lubrication system to have so high lubricant's levels, specific for Sampling, only around each Advanced Sampling's operation

Because it has to be very dense and constantly applied.  A hyperlubrication different than what is expected, designed and integrated for a simple Rejection application.  To reject roughly speaking means <10 consecutive containers.   But, Advanced Sampling may signifies the 173 consecutive Valves of a Filler Machine.  In other words, rarely or never the Conveyors’ Vendor has the know-how necessary to fulfill a correct high speed sampling.   Then, the Conveyors’ Vendor is the first who did not set a lubrication system adapt to assure high-speed sampling.    Not all Bottlers are so available to accept the unacceptable and the lubrication is, in the end, their only duty toward a correct Sampling in their own interest.  Separate lubrication means a hydraulic circuit providing extremely high amounts of lubricant originating by the same common circuit of the Bottling Line, but whose timing is controlled by a separate timer.  Timer changing the standard production duty-cycle to a heavy-duty, after an external command.  Command which in the simplest case, can be incoming by an Operator-controlled manual push-button.   Today, all Advanced Sampling operations can be made automatic directly in the Electronic Inspector.   They always exist opto-coupled potential-free digital inputs specific to start a Sampling operation, after an external command, as an example by the Programmable Logic Controller of the Filler Machine or as a timed output by the Lubrication Controller.

How much lubricant shall be applied in a sampling application, with respect to the lubrication it’d have been in case of simple rejection ?  

The amount depends on several factors, main being containers scalar speed and production. 

As an example, we consider the case of sampling for:

  • 500 ml;
  • PET bottles, 5-leaves petaloid bottom;
  • production 50000 bph;
  • linear speed 1570 mm/s.

Sampling table shall be:

  • 6-belts;
  • 3 m of active sampling area (table length > 3.5 m);
  • plastic polished belts;
  • optional guiding system for bottles;
  • lubricated > 4 times the amount recommended for a common rejection table.

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