Gear Pumps for Bulk Emulsion Trucks & MMUs

Bulk emulsion operations run on two different pumping jobs that are often confused. Surface transfer — moving unsensitized matrix from a plant tank to a delivery truck, reload pad to silo, or batch tank to mixing unit — is a low-pressure, low-shear duty where a rotary gear pump is the right tool. Downhole charging on a mobile mixing unit (MMU) pushes gassed, density-controlled product into a blast hole at higher pressure — that is progressive cavity territory, not a NAPCO gear pump application.

Surface Transfer vs. Downhole Charging

If you are specifying a bulk emulsion truck pump for loading or unloading matrix at ambient pressure, a stainless steel NAPCO gear pump delivers predictable flow, self-primes from a flooded suction, and rebuilds in the field. See our guides on bulk emulsion product types and ammonium nitrate emulsion pumping for product compatibility before sizing.

MMU manufacturers integrate both pump types on the same vehicle: a gear pump (or centrifugal auxiliary) for tank-to-tank transfer, and a PC pump for the charging hose. Do not substitute one for the other.

Truck & Skid Design Constraints

• Weight: PA200S net weight 114 lbs; PA300S 173 lbs — include in axle and skid calculations.
• Port size: 2″ NPT (PA200) vs 3″ NPT (PA300) — match manifold and hose ID to minimize friction loss.
• Bi-directional rotation: NAPCO pumps reverse flow by reversing the motor — useful for line clearing and tank-to-tank recovery.
• Relief valve: Set at or below 100 PSI tested rating; most surface transfer runs well below 50 PSI.

PA200S vs PA300S for Bulk Emulsion Duty

Use the pump sizing guide or sizing calculator to match fill rate (volume ÷ time) plus hydrostatic and line losses.

Piping, Heat & Priming

Emulsion viscosity rises when cold. Many bulk plants use traced or insulated lines and run the pump at reduced shaft speed until product reaches operating temperature. NAPCO gear pumps are self-priming when the suction line is flooded — verify suction strainer mesh and avoid air ingestion at tank low level. For heated matrix, confirm nitrile or Viton gear and seal compatibility with your supplier; see nitrile vs Viton gears.

Field Rebuild at Remote Mine Sites

Trucks and MMUs operate far from factory service. NAPCO PK300S and PK200S repair kits contain every wear part for a complete rebuild. Follow the step-by-step rebuild guide or watch the three-part series on repairs & replacement parts.