Bulk Emulsion Products: Types, Delivery, and Transfer

Bulk emulsion products are the water-in-oil ammonium nitrate emulsions used in large-scale mining, quarrying, and construction. They are manufactured and delivered in bulk, not in cartridges. Unsensitized matrix is typically handled as an oxidizer and is not a blasting agent until it is sensitized, usually at the hole. Some packaged and plant-sensitized grades are already finished product. This page is a practical map of the product family, how each grade is made and moved, and which ones a plant or truck can actually pump.

NAPCO does not manufacture explosives. We build the stainless steel rotary gear pumps that move unsensitized matrix, AN solution, and high-emulsion blends between tanks, silos, and loading trucks.

What bulk emulsion products are

A bulk emulsion is a water-in-oil emulsion. Concentrated ammonium nitrate solution is the dispersed phase. Fuel oil, mineral oil, or a waxed oil blend is the continuous phase. An emulsifier holds the interface together. The result is a thick, pumpable matrix that looks more like grease than like a liquid explosive.

Until that matrix is sensitized, it is typically handled as an oxidizer, not as a Class 1 explosive. Sasol’s Matrix product, a typical plant-made unsensitized emulsion, is classified UN3375, Class 5.1. The same UN 3375 / 5.1 assignment is the standard classification for emulsion-explosive matrices under ADR/RID. The safety case for bulk systems rests on that split: move a stable oxidizer over the road, then turn it into a blasting agent in the hole. Plant-sensitized bulk grades exist; they are the exception, not the transfer default.

Sensitization creates the “hot spots” that let the charge detonate. Two methods are used:

• Chemical gassing. A nitrite solution reacts in the emulsion and releases nitrogen bubbles, typically a few hundred microns across. Density is set at the truck, often in the 0.90 to 1.25 g/cc range on commercial systems such as Dyno Nobel TITAN.
• Physical sensitization. Glass or plastic microballoons, about 100 microns, are added at the plant. This is more common in packaged emulsion than in bulk.

Orica’s description is the cleanest commercial definition: a bulk emulsion is a controlled mixture of water and fuel, designed to be safe to handle, highly water-resistant, and effective at breaking rock once it is detonated. There is no single recipe. Viscosity, density, energy, and water resistance are tuned to the ground and the hole.

For the chemistry and why bulk systems displaced cartridges, see the 2022 review in Materials (PMC9318116). For the commercial product language, see Orica’s bulk emulsion primer.

Bulk emulsion vs ANFO vs packaged product

Three product classes get mixed together in search results. They are not interchangeable.

Straight ANFO is porous ammonium nitrate prill plus about 6% fuel oil. It is dry, free-flowing, and cheap. It has no water resistance. It is poured or blown, never pumped. If a blast pattern is dry and the rock wants heave more than shock, ANFO is still the default.

Packaged emulsion is plant-sensitized product in a film or cartridge. It is the right answer for small patterns, wet holes that cannot take a truck, and sites with no bulk infrastructure. It costs more per kilogram and is loaded by hand.

Bulk emulsion products are made and delivered in tonnes, not sticks. A mobile manufacturing unit (MMU) or a repump truck puts product straight into the hole. Density, blend ratio, and energy can change hole to hole. That is why bulk, not cartridges, is the dominant delivery form on large surface mines.

The practical split:

• Dry hole, cost first: ANFO
• Wet hole, or a need for coupling and higher velocity of detonation: straight or heavy emulsion
• Mixed ground, cost and water both matter: Heavy ANFO (an ANFO/emulsion blend)
• Remote site with a silo and no full MMU: repumpable unsensitized matrix
• Underground upholes, reactive ground, or fume-sensitive coal: a specialty bulk grade, not a generic matrix

The product family

“Bulk emulsion products” is a category, not a SKU. Plants and magazines usually stock more than one of the following.

Unsensitized emulsion matrix

The base product. Ammonium nitrate / hydrocarbon emulsion, typically a 5.1 oxidizer. Nelson Brothers PowerNel 1000 is a typical example: it must be blended with ANFO in various proportions to detonate. Related 1000-series grades (1000 NBG, 1000 FG) can also be chemically gassed with sodium nitrite. Matrix is what bulk plants make, what silos hold, and what transfer pumps move all day.

This is the fluid most bulk plants store and transfer. It is viscous, shear-sensitive, and corrosive to iron. Unsensitized matrix is also the lowest-hazard emulsion to pump, because it is not yet a blasting agent.

Site-mixed emulsion (SME)

The truck carries heated ammonium nitrate solution and the other raw materials. Nothing on the vehicle is a finished explosive. Mixing and sensitization happen on the pattern. Dyno Nobel’s TITAN SME system is the reference design: the mixture only becomes explosive after gassing in the borehole.

SME is a logistics product as much as a chemistry product. It cuts magazine inventory and keeps the high-hazard step at the hole.

Repumpable emulsion

The plant makes a finished, unsensitized matrix that is stable enough to store in a silo and pump again. A smaller truck, or a reload at a remote pad, gasses it into the hole. Dyno Nobel calls this out on TITAN XL 1000: the truck hauls unsensitized repumpable emulsion, then blends a small gassing stream as the product is pumped into the borehole.

Repumpable grades are specified for pumpability on purpose. If a matrix is too thick to transfer cleanly, the plant cannot use a silo-and-reload model.

Gassed / density-controlled emulsion

Once gassing chemical is added, density and velocity of detonation become variables. Sleep time matters. The gassing reaction does not stop on command, so density and VOD keep changing until the hole is shot. Temperature changes the rate. This is why bulk emulsion is a process, not a static product, after it leaves the truck hose.

NAPCO pumps are for the unsensitized side of this step: plant to tank, tank to truck, truck to silo. High-pressure downhole loading of already-gassed product is progressive cavity territory.

Heavy ANFO

A blend of emulsion matrix and ANFO, typically 20% to 70% emulsion by weight. Penn State’s mining course puts the practical range at 80:20 to 20:80 ANFO to emulsion. Adding emulsion coats the prill, raises density, and starts to give the charge water resistance. Adding more emulsion improves those traits and raises cost.

Heavy ANFO is the volume product on many surface mines because it buys some of the emulsion’s wet-hole performance at a lower cost than a straight emulsion column. Pumpability is blend-dependent. High-emulsion mixes can still move through a gear pump. High-prill mixes are augered.

Heavy emulsion

Industry usage treats “heavy emulsion” as a high-emulsion product, generally more than about 70% matrix. Water resistance and borehole coupling are better than Heavy ANFO. Velocity of detonation is higher. This is the wet-hole and hard-rock grade when the extra cost is justified.

Specialty grades

Commercial ranges add purpose-built variants on top of the core family: high-viscosity wet-hole grades (Orica Fortis Protect), oxygen-balanced low-fume grades, underground uphole grades, and reactive-ground products for pyritic or hot holes. The chemistry changes. The handling problem does not. They are still viscous, ammonium-nitrate-based emulsions that should not be sheared apart on the way to the truck.

How bulk emulsion is made and delivered

Two factory models feed the same blast pattern.

Fixed emulsion plant. Ammonium nitrate solution, oil phase, and emulsifier are combined under controlled shear. The plant stores unsensitized matrix in tanks or silos, then loads delivery trucks or MMUs. This is high-throughput, continuous-duty transfer. A 3-inch stainless gear pump is the usual NAPCO spec for that duty.

Mobile manufacturing unit. The truck is a small plant. It may carry matrix, or it may carry AN solution and make emulsion on the bench (SME). Gassing chemical is metered at the hole. Blend ratio, density, and energy are set per hole.

A third, hybrid model is the repump pad: a silo of unsensitized matrix at a remote mine, reloaded by a smaller truck. That model only works if the matrix stays pumpable after storage and transport.

Packaged product still exists for the holes a truck cannot reach. It is a different supply chain. It does not change the plant-and-truck problem this page is about.

What can be pumped

Getting this wrong is how plants buy the wrong pump, or try to pump a product that should be augered.

• Emulsion matrix (unsensitized): yes. Stainless steel rotary gear pump, surface transfer.
• Hot ammonium nitrate solution: yes. Stainless pump, temperature-rated elastomers.
• Repumpable / site-stored matrix: yes, if the grade was formulated to be pumped twice.
• Heavy ANFO, high emulsion content: sometimes. Treat it as blend-dependent. Confirm with the product TDS before you spec a pump.
• Heavy emulsion: usually yes on the matrix-rich side, same rules as matrix.
• Already-gassed product into a deep hole: not a gear-pump job. That is high-pressure, metered delivery. Progressive cavity pumps own that duty.
• Straight ANFO: no. Auger or pneumatic load.

The longer version of this split, including why iron fails in ammonium nitrate service, is on our ammonium nitrate and ANFO pumping page.

Handling rules that decide product quality

Bulk emulsion fails in two quiet ways: the emulsion breaks, or the metal in contact with it corrodes.

Shear. The oil-water interface is held by the emulsifier. High-speed impellers and overspeed progressive cavity pumps can tear that interface. Phase separation shows up as oil bleed, viscosity loss, and a product that will not gas or detonate the way the TDS promised. Gear pumps move discrete volumes between teeth at low shaft speed. That is why they are the established choice for plant and truck loading, not because they are “gentle” as a slogan, but because the kinematics do not accelerate the fluid the way a centrifugal pump does.

Temperature. Viscosity swings hard. Heated matrix at a plant may sit in the low hundreds of centipoise. The same product in a cold climate can exceed 1,000 cP. A positive-displacement gear pump still delivers a predictable volume per revolution. A viscosity-dependent seal does not.

Corrosion. Ammonium nitrate attacks ductile iron and carbon steel. Corrosion products contaminate the emulsion. Pitted bores chew gears and seals. Stainless housings and shafts are the global spec for any wetted path that sees AN solution or emulsion. Ductile iron stays on the fuel-oil and diesel side of the pad, not in the AN circuit.

Sleep time after gassing. Once the matrix is sensitized, density and VOD keep moving. That is a blast-design problem, not a transfer-pump problem. Do not store gassed product in a transfer line and expect the same density you set at the truck.

Classification. Unsensitized matrix is handled as an oxidizer. Sensitized product is a blasting agent or explosive. Plant transfer should stay on the unsensitized side of that line whenever the process allows it.

Transfer equipment for plants and trucks

NAPCO’s role in this product family is narrow and specific: surface transfer of unsensitized matrix, AN solution, and pumpable high-emulsion blends. Tank to tank. Plant to truck. Silo to reload. Not borehole injection.

PA300S: plant and truck loading

The PA300S 3-inch stainless steel gear pump is the plant workhorse. 158 GPM at 280 RPM and 10 PSI, 140 GPM at 100 PSI. Tested maximum is 100 PSI. Most surface transfer runs well below 50 PSI. Net weight 173 lbs. Rebuild with a PK300S service kit in 2 to 5 hours.

PA200S: skids, smaller batches, auxiliary duty

The PA200S 2-inch stainless steel gear pump is 69 GPM at 190 RPM, same 100 PSI ceiling, 114 lbs. It fits skid systems, smaller batch plants, and the auxiliary circuits on a truck or pad where the 3-inch pump is oversized.

Elastomers and service

Nitrile gears, rated to 240°F, are standard for mineral-oil emulsions. Viton gears are the option for hot AN solution or chemically aggressive formulations. Viton seals are standard on every NAPCO pump. Both stainless models are self-priming and bi-directional, so a truck can load and unload without re-plumbing.

For the full selection logic, including why centrifugal pumps do not belong on this fluid, use the emulsion explosive pump selection guide.

What not to spec a NAPCO pump for

High-pressure downhole loading, often 500 PSI and above down a blast hole, is progressive cavity duty. Gear pumps win on plant flow, field rebuild, dry-run tolerance, and cost. They lose on metered high-pressure injection. Mixing those two jobs is how sites buy the wrong machine twice.

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