The primary difference between a filling machine used for flammable products and one that is non flammable is the use of intrinsically safe components of the operating system so that auto ignition of these products is avoided. This can be accomplished with all pneumatic components or an electrically isolated control panel or a combination thereof. One disadvantage of purely pneumatic systems is the use of pneumatic logic control components that are subject to timing errors if the user's system air is not supplied at consistent rates and pressure. Electrically operated systems installed in intrinsically safe control panels of these filling machines are more functionally reliable and offer greater elegance of operating controls.  These systems can be installed in an overflow filling machine, a time gravity filling machine and piston filling machine depending on the flow characteristics of the products being filled. 

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Overflow Filling Machine for Flammable Chemicals

Flammable chemical products with thin viscosities that are filled into narrow opening bottles, cans and canisters and be filled on either the Overflow Filling Machine or the Time Gravity Filling Machine. The overflow filling machine is the filling machine of choice for distilled products filled in glass and plastic bottles in the liquor industry.  The primary reason for this is that the fill height of the containers are visible to the consumer and the overflow filling machine guarantees that all bottle fill heights will be the same within 1/16".  This is particularly important in the case of liquor filled into glass bottles where the manufacturing variances of the glass can be significant. Solvents such as acetone and methanol that are filled in semi translucent bottles are also best filled on this type of filling machine since the fill height in the bottle is also readily apparent to the consumer.

Some flammable products should not be pressurized because the flashpoint of the product may be lowered to a level that makes it unsafe for commercial filling operations. Also, continued recirculation of the product in an overflow filling machine could increase venting of the product to unsafe levels depending on the operator's control and design of the hazardous location filling area.

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Time Gravity Filling Machine for Flammable Chemicals

Like the overflow filling machine for flammables described above, the Time Gravity Filling Machine is also useful for flammable chemical products with thin viscosities into narrow opening bottles, cans and canisters. It is also useful for filling large containers of solvent based chemicals where the top of the container cannot be sealed and where it is not practical to pressurize or recirculate the product.

Although there are inherent accuracy issues with time gravity filling machines, they are relatively cost effective machines and the producers are generally not as concerned about precision of filling accuracy of these commodity based products. Also, since these machines are often used for bulk filling applications of flammable products, the accuracy errors produced by timing errors become relatively small as a percentage of total fill volume.

(click to enlarge)  Piston Filling Machine for Flammable Chemicals

The most common types of flammable products filled in a piston filling machine are solvent based coatings and paints into cans and to a lesser degree, into bottles. Coatings and paints by nature are thicker viscosity and require a positive displacement delivery system to fill a precise quantity of product under pressure regardless of viscosity changes. Products like paint would be too thick to recirculate in an overflow filling machine or flow out of a time gravity filling machine. Many piston fillers on the market use pneumatic only logic control for operation because the piston filling machine operating system is quite simple; only manual adjustments are made to change the fill volume.  Although piston fillers do have a disadvantage in long setup times,  this is generally not an issue for paint producers since the generally accepted fill sizes are limited.