{"id":3203,"date":"2023-01-27T10:30:00","date_gmt":"2023-01-27T10:30:00","guid":{"rendered":"https:\/\/www.despatch.com\/blog\/?p=3203"},"modified":"2023-04-14T19:46:23","modified_gmt":"2023-04-14T19:46:23","slug":"does-your-process-require-a-class-a-oven","status":"publish","type":"post","link":"https:\/\/www.despatch.com\/blog\/does-your-process-require-a-class-a-oven\/","title":{"rendered":"Does Your Process Require a Class A Oven?"},"content":{"rendered":"\t\t
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Do you process flammable products or remove combustible materials in an industrial oven? If you do, you need a Class A oven<\/a> that meets NFPA\u00ae 86 requirements. Flammable volatiles posing a potential explosion or fire hazard can come from paints, powders, inks, and adhesives. Potential threats can also come from finishing processes, such as dipped, coated, sprayed, impregnated materials, and polymerization or other molecular rearrangements. Combustible materials that can pose threats include substrates, wood, paper, plastic pallets, spacers, and packaging materials.<\/p>

It doesn\u2019t take much for a serious injury to occur when processing flammable products or combustible materials. Inadequate operator training, poor maintenance, and improper equipment application can all cause serious injuries. According to the Operational Health and Safety Administration<\/a> (OSHA), there were\u00a02,654,700\u00a0workplace injuries in 2020<\/a>, with 4,764 fatal. Industrial accidents like these can cost companies a bundle.<\/p>

Training operators to understand equipment ratings and how they impact product processing helps prevent workplace injuries. So, does complying with the latest safeguards minimize explosion hazards. Complying with existing safeguards should be a priority at your company, with no discounts or deviations. Put another way, ignoring industrial oven safety features or removing safeguards is courting disaster, the fallout of which could threaten your company’s existence.<\/p>\t\t\t\t\t<\/div>\n\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/div>\n\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/section>\n\t\t\t\t

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NFPA 86 Standard for Ovens and Furnaces<\/h2>\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/div>\n\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/section>\n\t\t\t\t
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Understanding and complying with the NFPA 86 standard for industrial ovens and furnaces safeguards the operation of direct fuel-fired ovens used to process flammable solvents or combustible materials. NFPA 86 covers all possible application requirements. That includes everything from material suitability comprising an oven, to the safety and precautionary interlocks serving as fail-safes, and everything in between. NFPA 86 also provides a dedicated section covering the full spectrum of an oven\u2019s specialized functionality and specific role depending on oven type. (Despatch Class A ovens<\/a>\u2014whether benchtop, walk-in, or conveyor\u2014all meet NFPA 86 requirements.)<\/p>

Consult a copy of NFPA 86 Standard for Ovens and Furnaces<\/a> from the National Fire Protection Association (NFPA) to learn the latest safeguards to minimize explosion hazards.<\/p>\t\t\t\t\t<\/div>\n\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/div>\n\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/section>\n\t\t\t\t

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Class A Oven Requirements<\/h2>\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/div>\n\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/section>\n\t\t\t\t
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Three rating classifications of ovens exist\u2014Class A, Class B, and explosion-proof. Class B ovens are more straightforward and basic than Class A ovens. Class B ovens support clean processes, which include no flammable volatiles or combustible materials being heated. Electrically-heated Class B ovens must have an airflow safety switch, a manual reset excess temperature control, and backup contactors as fail safes.<\/p>

The explosion-proof rating can be expensive compared to Class A and B. This rating isn’t the same as Class A requirements and shouldn\u2019t be confused with it. Explosion-proof industrial ovens are complex thermal processing units with requirements far too extensive to cover in detail in an article like this. NFPA 70<\/a> addresses this rating if you want to learn more. NFPA upgraded the standard for 2023.<\/p>\t\t\t\t\t<\/div>\n\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/div>\n\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/section>\n\t\t\t\t

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Requirements for Class A Ovens (gas-fired)<\/h3>\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/div>\n\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/section>\n\t\t\t\t
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Class A applications require specially designed ovens for processing direct, gas-fired equipment or products involving flammable volatiles or combustible materials. These critical features include:<\/p>\t\t\t\t\t<\/div>\n\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/div>\n\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/section>\n\t\t\t\t

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  • Explosion relief area:<\/strong> Incorporating a panel or special doors provides some form of a pathway to allow a controlled release of pressure from inside the oven in case of an explosion. The required explosion-relief area must be equivalent to at least one-fifteenth of the oven’s interior volume or a 15:1 volume-to-venting-area ratio (cu ft\/sq. ft).<\/li>
  • Positive forced ventilation:<\/strong> Class A ovens must have positively forced ventilation sized to accommodate the amount of combustible product in the maximum oven load. That means the oven needs an exhaust fan separate from the current recirculation fan.<\/li>
  • Airflow safety switch:<\/strong> Class A ovens need an exhaust fan motor starter and airflow switch interlocked to prevent operation of the heating units unless the exhaust fans are running.<\/li>
  • Purge timer \u2014 <\/strong>A purge timer ensures that the oven purges flammable vapors and gases from the chamber before the oven activates the heating elements. Failure to maintain the minimum required pre-ignition purge airflow stops the pre-ignition purge and resets the purge timer.<\/li>
  • Manual Reset Excess Temperature Controller<\/strong>\u2014<\/strong>\u00a0This controller is set at approximately 50\u00b0F higher than the oven setpoint or maximum rated temperature. If the industrial oven or furnace exceeds the temperature setting, the hi-limit shuts down the burner.<\/li>
  • Flame Safety\/Spark Ignition Control<\/strong>\u2014<\/strong>\u00a0Direct gas-fired industrial ovens feature a flame supervision device. The control sends a high-voltage signal to the spark plug for ignition at startup by opening the pilot gas valve. That allows the oven to ignite the pilot flame. Once the control detects a pilot flame, the high-voltage signal stops and the main gas valves open. That permits ovens to go to high fire and start operations. If the oven fails to detect a pilot flame, the flame safety stops the ignition attempt.<\/li>
  • High-Low Gas Pressure Switch<\/strong>\u2013<\/strong>\u00a0If a sensor detects that the gas flow is too high or too low, the switch automatically shuts the oven down. The oven must supply even gas pressure to maintain the correct air-to-fuel ratio for proper flame characteristics and prevent combustible vapor build-up.<\/li><\/ul>\t\t\t\t\t<\/div>\n\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/div>\n\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/section>\n\t\t\t\t
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    In addition, companies must attach a completed safety design data form for Class A ovens or ovens if solvent atmospheres are present. This safety form must include the solvent quantity per hour or batch, purge time, operating temperature, and exhaust rating.<\/p>\t\t\t\t\t<\/div>\n\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/div>\n\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/section>\n\t\t\t\t

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    Requirements for Class A Ovens (electrically-heated)<\/h2>\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/div>\n\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/section>\n\t\t\t\t
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    Electrically-heated Class A industrial ovens need some additional unique features not found in direct-fired Class A ovens, including:<\/p>\t\t\t\t\t<\/div>\n\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/div>\n\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/section>\n\t\t\t\t

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