Mixers for Flammable Liquids and Hazardous Area Applications
Mixing flammable liquids requires equipment designed not only for effective blending and circulation, but also for the specific safety requirements of hazardous environments. Applications involving hydrocarbons, alcohols, ethanol, spirits and other volatile liquids can create flammable vapours, making the correct mixer configuration, drive system, sealing arrangement and hazardous-area certification essential.
Mixquip provides agitators and mixers that can be configured for applications involving flammable liquids and solutions. Depending on the process and installation requirements, mixer configurations may incorporate flameproof motors, pneumatic drives and hazardous-area rated components.
For large storage and processing tanks, side entry agitators can provide an efficient solution for maintaining circulation, blending liquids and keeping products consistent throughout the vessel.
What Mixers Can Be Used for Flammable Liquids?
The appropriate mixer depends on the liquid being processed, tank design, hazardous-area classification and operating conditions.
A range of Mixquip agitators, including top entry mixers, clamp-on mixers, IBC mixers and high shear mixing equipment, can be configured with intrinsically safe or flameproof motors or pneumatic drives where required for flammable-liquid applications.
For larger tanks, Mixquip’s Series 110 side entry agitator provides another mixing option, particularly where effective circulation and blending are required within large-capacity vessels.
Side entry agitators position the mixing equipment through the side wall of the tank rather than through the top. This configuration can provide strong circulation while allowing the external drive components to remain accessible for servicing.
Hazardous Area Requirements for Side Entry Agitators
When side entry agitators are used with flammable liquids, safety requirements extend beyond simply specifying a flameproof motor.
For these applications, the primary focus is on maintaining containment integrity, preventing ignition and reducing the risks associated with flammable liquids and vapours.
Australian Standards AS 1692 and AS 1490 do not mandate that the mechanical seal of a side entry mixer must be certified as “fire safe” or “fire resistant” for a specified period. Instead, compliance focuses on preventing and controlling hazards before a fire occurs.
This distinction is important because requirements applying to the storage tank or isolation valves should not automatically be interpreted as requirements applying to the mixer’s mechanical seal.
Are Side Entry Mixer Mechanical Seals Fire Rated?
A common misconception is that the mechanical seal on a side entry agitator must carry the same type of fire rating associated with other parts of a flammable-liquid storage installation.
AS 1692 specifies requirements relating to the construction of steel tanks. Depending on the installation, AS 1940 may also require the tank system to provide a specified level of fire resistance.
Tank product-discharge isolation valves may similarly need to meet relevant fire-safe requirements.
The mechanical seal on a side entry mixer has a different function. A dynamic mechanical seal cannot realistically be made completely fireproof. In a severe fire that engulfs the tank and mixer assembly, components such as elastomers and face-loading springs can ultimately fail.
For this reason, the focus for the mixer seal is on hazardous-area suitability, containment and providing mechanisms that can control the product if a seal develops a leak.
Key Safety and Compliance Considerations
IECEx and ATEX Hazardous Area Certification
Equipment used in a hazardous area must be appropriate for the applicable zone classification.
For side entry agitator applications, the seal assembly should be certified for the relevant hazardous-area classification. Depending on the installation, this may involve areas classified as Zone 1 or Zone 0 inside the tank.
Temperature classification is also important. For applications such as ethanol and high-proof spirits, a T4 temperature classification may be specified to ensure equipment surface temperatures and heat generated through operation remain appropriately controlled for the application.
The exact hazardous-area requirements should always be determined according to the specific installation, liquid and applicable engineering assessment.
Tank Shut-Off Device
One of the most important safety features for a side entry agitator is a mechanical tank shut-off mechanism.
The shut-off device allows the agitator shaft to be withdrawn and mechanically sealed against the inside of the tank shell from outside the vessel.
If the mechanical seal begins leaking or fails, the shut-off mechanism can contain the liquid inside the tank. This allows maintenance personnel to work on or replace the seal without relying solely on the damaged seal to maintain product containment.
For facilities handling flammable liquids, this provides an important additional level of protection.
Double Mechanical Seal and Pressurised Containment
Applications requiring a high level of containment may use a double mechanical seal with an independent pressurised barrier-fluid system.
The pressurised barrier provides additional separation between the process liquid and the external environment.
If the primary seal face begins to fail, the arrangement is designed so that barrier fluid moves towards the process rather than allowing the flammable product to escape through the seal into the surrounding area.
This configuration can be particularly valuable where leakage of flammable vapours or liquids needs to be tightly controlled.
Applications for Hazardous Area Mixers
Mixers configured for flammable-liquid and hazardous-area environments can be used across industrial and sanitary applications.
Petrochemical and Hydrocarbon Processing
In petrochemical and hydrocarbon applications, mixers can be used for industrial oil blending, tank circulation and maintaining product uniformity.
Large storage tanks may require continuous or intermittent circulation to keep components evenly distributed and reduce settling or stratification. Side entry agitators can be particularly suitable for these large-volume applications because they generate strong circulation while providing external access to the drive and sealing components.
Alcohol and Steriliser Production
Alcohol-based products used in steriliser and related sanitary applications require careful consideration because of their flammability.
Mixer selection should therefore account for both the sanitary requirements of the process and the hazardous-area classification of the installation.
Appropriately configured agitators can provide the mixing required for product consistency while incorporating suitable drives, seals and hazardous-area components.
Spirits and High-Proof Drinks
Distilleries and beverage manufacturers handling high-proof alcohol also need mixing equipment suitable for environments where ethanol vapours may be present.
Sanitary mixer construction can be combined with appropriate hazardous-area equipment for blending and processing spirits and other high-alcohol beverages.
Depending on the installation, considerations may include hazardous-area certification, temperature classification, seal configuration and containment requirements.
Why Use Side Entry Agitators for Flammable Liquid Applications?
For large tanks, side entry agitators provide several practical advantages.
Their angled impeller configuration creates strong circulation throughout large-capacity vessels while helping reduce power demand. External drive components also improve accessibility for inspection and maintenance.
For hazardous-area applications, side entry agitators can additionally incorporate appropriate sealing and containment arrangements to help manage the risks associated with flammable liquids.
The mixer can be engineered around factors including:
- Tank dimensions and working volume
- Product viscosity and density
- Required circulation and blending performance
- Hazardous-area zone classification
- Temperature classification
- Mechanical seal requirements
- Sanitary or industrial construction requirements
- Tank shut-off requirements
- Barrier-fluid and double-seal requirements
Selecting the Right Mixer for Flammable Liquids
There is no single mixer configuration suitable for every flammable-liquid application.
The correct solution depends on the characteristics of the liquid, tank geometry, mixing objective, operating environment and hazardous-area classification. A petrochemical oil-blending tank, for example, will have different process and construction requirements from a sanitary vessel handling ethanol or high-proof spirits.
Mixquip can assist with selecting and configuring mixing equipment around the requirements of the application, from drive and impeller selection through to mechanical seals and hazardous-area considerations.
For large-tank applications, explore Mixquip’s side entry agitators or contact the Mixquip team to discuss your process and hazardous-area mixing requirements.
Frequently Asked Questions
Can mixers be used with flammable liquids?
Yes. Mixers can be configured for flammable-liquid applications using equipment appropriate for the relevant hazardous environment. Depending on the installation, this can include flameproof motors, pneumatic drives and appropriately rated components.
What industries use hazardous-area mixers?
Common applications include petrochemical and hydrocarbon processing, oil blending, alcohol-based steriliser manufacturing, distilling, high-proof beverage production and other chemical or industrial processes involving volatile liquids.
Do side entry agitator mechanical seals need to be fire rated?
AS 1692 and AS 1490 do not specifically require a side entry mixer’s mechanical seal to be certified as fire safe or fire resistant for a defined fire-engulfment period. The focus is instead on containment integrity, explosion prevention and appropriate hazardous-area controls.
What happens if a side entry agitator seal fails?
A properly configured side entry agitator can incorporate a mechanical tank shut-off mechanism. This allows the shaft to be withdrawn and the tank opening mechanically isolated so that liquid remains contained while the mechanical seal is serviced or replaced.
Why use a double mechanical seal for flammable liquids?
A double mechanical seal with an independent pressurised barrier-fluid system provides an additional layer of containment. If the primary seal face fails, the system is designed to direct barrier fluid towards the process rather than allowing the flammable process liquid to escape into the surrounding environment.
Are side entry agitators suitable for spirits and ethanol?
Side entry agitators can be configured for alcohol and high-proof beverage applications where appropriate. The specific installation should account for sanitary requirements, hazardous-area classification, temperature class and suitable sealing and containment arrangements.