Explosion-Proof Liquid Fillers and Monobloc Filler-Cappers – Part 1

June 5, 2026

Laub\Hunt Packaging Systems professionally designs and manufactures high-quality, customized explosion-proof liquid fillers and monobloc filler-cappers. These systems prioritize safety in hazardous environments.

Explosion-Proof Liquid Filling Systems: Engineering Design, Compliance, and Best Practices


A Technical White Paper for Manufacturing and Plant Leadership


1. Introduction

Explosion-proof liquid fillers and monobloc filler-cappers are critical in industries such as chemical processing, pharmaceuticals, petrochemicals, and coatings. These machines are designed to safely handle flammable liquids in classified hazardous locations where explosive atmospheres may be present.

Unlike conventional equipment, explosion-proof systems are engineered not to prevent explosions entirely, but to contain and control ignition events, ensuring they do not propagate into the surrounding environment.


2. What Does “Explosion-Proof” Mean?

The term explosion-proof is often misunderstood. It does not mean that equipment cannot explode. Rather, it means:

Equipment is designed to contain an internal explosion and prevent ignition of the surrounding hazardous atmosphere.

Key Characteristics:

●    Flame containment: Enclosures withstand internal pressure from an explosion

●    Flame path cooling: Escaping gases are cooled below ignition temperature

●    No external ignition: Sparks, arcs, or hot surfaces cannot ignite ambient gases

Comparison with Intrinsically Safe Systems:

●    Explosion-proof: Contains explosions within robust enclosures

●    Intrinsically safe: Limits electrical energy to prevent ignition entirely

Both approaches are often used together in advanced filling systems.

 

3. Why Explosion-Proof Design Matters

In liquid filling operations, ignition risks are elevated due to:

●    Volatile vapors (e.g., alcohols, solvents, fuels)

●    Static electricity during fluid transfer

●    Mechanical motion and friction

●    Electrical switching components

Failure to address these risks can result in:

●    Catastrophic explosions

●    Equipment destruction

●    Regulatory violations

●    Severe injury or loss of life

Explosion-proof design is therefore not optional—it is foundational to safe plant operation and regulatory compliance. 

4.1 NEC / North America (Class/Division System)

●    Class I, Division 1: Explosive gases present under normal conditions

●    Class I, Division 2: Explosive gases present under abnormal conditions

4.2 ATEX / IECEx (Zone System)

●    Zone 0 / EPL Ga: Continuous hazard

●    Zone 1 / EPL Gb: Likely during operation

●    Zone 2 / EPL Gc: Unlikely, short duration

Modern filling systems are often designed to meet both systems for global deployment.

See more in Parts 2 and 3 

Contact Laub/Hunt Packaging Systems for more information.



Explosion-proof liquid fillers and monobloc filler-cappers are critical in industries such as chemical processing, pharmaceuticals, petrochemicals, and coatings.

15 Quality Assurance Checks: Safety, Durability, and Final Sign-Off - Part 2
October 23, 2026
For bleach, detergents, and other foaming or chemically aggressive products, a dedicated suds test is performed to simulate actual operating conditions.
The 15 Quality Assurance Checks Every Machine Must Pass Before Shipment
October 18, 2026
Before any liquid filler leaves our facility, it must pass a structured series of 15 quality assurance checks that cover lubrication, mechanical alignment, leak integrity, safety, hygiene, and long‑run performance.
October 6, 2026
What Happens During Factory Acceptance Testing (FAT) Stages 5 - 7 Stage 5: Surface Finish, Coatings, and Safety Coatings and Finishes FAT also includes a review of protective coatings and surface finishes, important for both corrosion resistance and cleanability. Checks include: ● Confirming two coats of chlorinated rubber paint or equivalent on all iron surfaces where specified, especially for bleach and detergent applications. ● Ensuring no paint on any thread surfaces or leveling screws so adjustments remain possible. ● Verifying that brass wearing surfaces on sliders are not being scraped and are correctly aligned. These guidelines emphasize the importance of appropriate coatings and cleanable surfaces, particularly for food, beverage, and aggressive chemical products. Laub\Hunt’s attention to such details at FAT ensures long‑term durability and sanitation. Safety Devices and Nameplate As part of FAT, Laub\Hunt verifies: ● Presence and function of limit switches at the infeed star and on the infeed conveyor. ● Availability and accessibility of grease fittings and other routine‑maintenance points. ● Correct, legible nameplate data (model, serial, ratings), which customers will use for documentation and future parts orders. Best practices call for safety verification (guards, interlocks, e‑stops) and accurate identification plates as prerequisites for shipment. Laub\Hunt incorporates these checks to help customers meet safety and compliance requirements. Stage 6: Long‑Run Performance Trials Extended Run Test FAT is not limited to quick spot checks. Laub\Hunt performs extended run tests where the machine operates for a couple of hours at or near production speeds with water and bottles. During this period, technicians evaluate: ● What wears: observing cams, followers, sliders, and seals for abnormal heat, friction, or polish. ● What rubs or squeaks: diagnosing any contact or misalignment indicated by noise. ● Smooth transfer of bottles across bridge plates, transfer plates, donut plates, and conveyor chains, ensuring no stumbling or misfeeds. Longer‑duration FAT runs are essential for revealing latent issues that short trials miss—such as thermal growth, creeping misalignment, or intermittent jams. Laub\Hunt’s long‑run tests follow that logic and are documented as part of the FAT record. Torque Limiter and Overload Behavior Laub\Hunt’s checklist also calls for verifying the torque limiter: It must be adjustable so the machine can be pulled back while running and restarted from any position. During FAT, Laub\Hunt: ● Tests overload conditions to ensure the torque limiter slips or releases as designed. ● Confirms that the machine can resume operation without binding after an overload event. Tests of overload and emergency behavior ensures both equipment protection and operator safety. Including this in FAT means customers receive a machine whose protective systems have already been proven under controlled conditions. Stage 7: Special Tests for Detergent and Chemical Applications Suds and Chemical‑Behavior Tests For fillers intended for bleach, detergents, and other foaming or chemically aggressive products, Laub\Hunt performs specialized tests beyond standard water trials. These include: ● “Suds tests” using detergent or ammonia solutions to observe foam behavior in the bowl, valves, and overflow paths. ● Checks that level controls remain stable and that foam does not cause chronic false readings or spills. ● Validation that seals, coatings, and materials in contact with test solutions behave as designed. It is necessary to test performance under realistic process conditions, including foaming and temperature variations, before shipment. Laub\Hunt’s suds and chemical‑behavior tests are the result of decades’ experience in the bleach and household‑chemical markets. Stage 8: Spares, Accessories, and Documentation Counting Stars, Guides, and Spares A comprehensive FAT also ensures that everything promised in equipment order is present and accounted for. Laub\Hunt technicians: ● Count and record the number of stars and guides shipped. ● Verify the number of spare valves and confirm they are fully assembled and ready to use. ● Confirm that a grease gun and a tube of Parker O‑Lube (or equivalent) are packed with the filler. Best practices include checks that all auxiliary equipment, tools, and documentation are present, as these items are often critical to smooth commissioning. Final Documents and FAT Report Throughout the FAT, Laub\Hunt records: ● Test results, observations, and any deviations from expected performance. ● Adjustments made and final “zero settings” (e.g., fill volumes, speeds, and key alignment points). ● Outstanding minor items, if any, with a plan for resolution. Best practices call for a formal FAT report and acceptance certificate once criteria are met, with any minor punch‑list items documented separately. Laub\Hunt follows this model, ensuring that you have a shared, written record of what was tested and accepted before shipment. What FAT Means for You When Factory Acceptance Testing is complete, you receive a filler that has already: ● Been fully lubricated, aligned, and checked for mechanical integrity. ● Passed dry and wet functional checks, including leak tests, safety verifications, and extended runs. ● Demonstrated performance with your bottles under realistic conditions. ● Had its accessories, spares, and documentation verified and packed. Industry standards—and Laub\Hunt’s decades in liquid filling—show that this investment in the FAT dramatically reduces startup time, rework, and risk at your plant. By the time your machine reaches your dock, the heavy troubleshooting has already been done, allowing installation and commissioning to focus on integration and optimization rather than basic fixes. Contact us for more information. Also review stages 1-2 and stages 3-4.