What Are Emulsion Explosives?
Bulk emulsion explosives are a complex matrix of ammonium nitrate dissolved in water, then emulsified in mineral oil. The result is a thick, pumpable slurry with oxygen-balance characteristics that make it safer and more robust than dynamite or straight ammonium nitrate-based products.
The emulsion is created by combining an aqueous ammonium nitrate solution with an oil phase in precise ratios, using mechanical mixing and emulsifying agents. The stability of this emulsion depends on maintaining the integrity of the oil-water interface throughout production, transfer, and loading. Any process that breaks the emulsion structure can degrade the product, creating safety and performance issues.
Emulsion explosives offer superior performance for mining operations because they are less sensitive to detonation by friction or shock than older explosives, yet provide excellent blast energy for ore fragmentation. They are also more economical than dynamite-based products, contributing to their widespread adoption globally.
Why Pump Selection Matters for Emulsion Explosives
Shear Sensitivity
The emulsion structure is shear-sensitive. Centrifugal pumps and progressive cavity pumps operating at high speeds can shear the emulsion, breaking down the oil-water interface and destabilizing the product. This manifests as phase separation, where oil bleeds out and the emulsion loses viscosity and stability.
NAPCO gear pumps operate at controlled speeds (typically 500–1500 RPM depending on size) and apply gentle, consistent pressure rather than high shear. This preserves emulsion integrity throughout the transfer process.
Viscosity Changes with Temperature
Emulsion explosives are highly temperature-dependent. Viscosity increases dramatically in cold conditions (winter mining operations) and can become thin at elevated temperatures. A pump that relies on viscosity for internal sealing (like some progressive cavity pumps) will have higher internal slip in cold conditions, reducing efficiency and output.
NAPCO gear pumps maintain consistent output regardless of temperature because they use mechanical meshing of the gears to create displacement, not viscosity-dependent sealing. This means reliable, predictable flow from the hot summer transfer trucks to the coldest winter mine sites.
Abrasive Particles
Some emulsion formulations contain abrasive particles such as glass microbeads for sensitivity modification or detonation velocity tuning. These particles can damage the fine internal tolerances of centrifugal pumps. NAPCO gear pumps, with their robust design and generous internal clearances, handle these additives without degradation.
Why Stainless Steel Is Essential for Emulsion Explosives
Ammonium nitrate is inherently corrosive to carbon steel and cast iron. Even brief exposure causes pitting and corrosion that leads to rust particles contaminating the product and eventual leaks. In tropical climates or high-humidity environments, corrosion accelerates dramatically.
NAPCO stainless steel pumps (PA300S, PA200S) are manufactured from 316L stainless steel with stainless steel shafts. This ensures that the entire wetted path—housing, gears, shaft, and internal components—resists ammonium nitrate corrosion. Mining operations worldwide trust stainless steel pumps for emulsion transfer because corrosion resistance is not an option; it is a requirement.
The investment in stainless steel pays for itself through multi-year service life without corrosion failures. A ductile iron pump exposed to emulsion explosives would corrode severely within months, requiring replacement. A stainless pump operates reliably for eight to ten years or more.
Why NAPCO Gear Pumps Excel for Emulsion Explosives
Self-Priming from Storage Tanks
NAPCO gear pumps are self-priming and can draw directly from bulk storage tanks without requiring external priming or suction assistance. This is essential for mobile loading trucks and manufacturing plants where quick setup and reliable startup are critical. A centrifugal pump requires careful priming and may lose prime if the suction line cavitates.
Bi-Directional Operation
NAPCO gear pumps can operate in forward and reverse, enabling loading and unloading without switching pump direction or reconfiguring lines. This flexibility is valuable for transfer trucks that alternate between loading at manufacturing plants and unloading at mine sites.
Low Shear Compared to Centrifugal Pumps
Centrifugal pumps accelerate fluid to high velocities, which induces shear stress. This shear damages the emulsion structure. Gear pumps generate displacement by advancing fluid between gear teeth and the housing without acceleration, minimizing shear and preserving emulsion integrity.
Consistent Flow Rate
NAPCO gear pumps deliver consistent, predictable flow rate independent of viscosity or pressure fluctuations (within rated limits). This consistency makes batch sizing and loading schedules reliable, avoiding the output variation that centrifugal pumps exhibit with changing fluid properties.
Recommended NAPCO Configurations for Emulsion Transfer
PA300S: High-Volume Bulk Transfer
Standard Flow Rate
158 GPM (600 RPM)
Pressure Rating
350 PSI (continuous)
The PA300S is the standard for bulk emulsion transfer trucks and manufacturing plant operations. Its 158 GPM capacity enables rapid loading and efficient production rates. The larger displacement means lower shaft speed and minimal internal slip, resulting in consistent output even as emulsion viscosity changes with temperature.
The PA300S is fully stainless steel with 316L housing and stainless shaft, essential for ammonium nitrate resistance. Factory-matched repair kit PK300S enables field rebuilds.
PA200S: Mobile Mixing Units and Smaller Operations
Standard Flow Rate
69 GPM (600 RPM)
Pressure Rating
350 PSI (continuous)
The PA200S is ideal for mobile mixing trucks, smaller mining operations, and remote mine sites where lower volume and lightweight equipment are advantages. At 69 GPM, it handles smaller batches and on-demand loading with excellent reliability.
Like the PA300S, the PA200S is fully stainless steel. Factory-matched repair kit PK200S supports field service.
Gear Material Selection for Emulsion Applications
Nitrile Gears: Standard for Most Emulsion Applications
NAPCO stainless steel pumps are supplied with nitrile (NBR) elastomer gears by default. Nitrile offers excellent compatibility with mineral oil-based emulsions and resists the ammonium nitrate aqueous phase. The material maintains elasticity up to 240°F, suitable for ambient and moderately elevated operating temperatures.
Nitrile gears are standard because they offer the best balance of chemical resistance, cost, and performance for typical emulsion explosives operations.
Viton Gears: High-Temperature Emulsion Transfer
When operating at elevated temperatures (above 180°F sustained), Viton (FKM) elastomer gears are recommended. Viton maintains elasticity to 400°F and provides superior thermal stability. This is common in tropical mining regions or operations where the emulsion is heated prior to transfer for viscosity control.
Where NAPCO Pumps Operate Globally
NAPCO stainless steel gear pumps are deployed in emulsion explosives operations across the mining industry worldwide:
Transfer Trucks
Mobile loading units that travel between manufacturing plants and remote mine sites.
Mobile Mixing Units
On-site mixing equipment at large mining operations where emulsions are blended at the mine.
Manufacturing Plants
Production facilities where bulk emulsions are manufactured and transferred to truck loading bays.
Mine Site Storage and Dispensing
Stationary systems for storing and dispensing emulsion explosives to loading trucks and blast units.
Maintenance in Remote Mine Locations
Mining operations often occur in remote locations where shipping equipment to a factory for repair is impractical. NAPCO addresses this with factory-matched repair kits designed for field rebuilds.
Factory-Matched Repair Kits
NAPCO supplies PK300S kits for PA300S pumps and PK200S kits for PA200S pumps. These kits include all internal components needed for a complete rebuild: gears, shafts, seals, bearings, and fasteners. The kits are factory-matched to ensure proper fit and performance without custom machining or adjustments.
A qualified technician at a mine site can remove the pump, disassemble it, install the repair kit components, reassemble, and return the pump to service within hours. This eliminates multi-week factory turnaround times and ensures mining operations stay on schedule.
Full Rebuild Without Factory Return
Because repair kits are field-installable, mine sites and operations centers can maintain spare pumps and kits in inventory, enabling rapid swaps when service is needed. The failed pump can be rebuilt on-site or shipped to NAPCO for overhaul at a later date when the operation is not time-critical.
Related Technical Resources
Ready to Specify a Pump for Emulsion Transfer?
NAPCO engineering specialists have decades of experience in emulsion explosives operations. Provide your flow rate, operating temperature, and site conditions, and we'll recommend the optimal configuration with sizing and delivery options.
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