A syringe assembly for a hydraulic fracturing system includes a syringe having a material chamber, a base fluid chamber, and a piston. The material chamber is configured to be fluidly connected to a fluid conduit. The piston retracts to draw material into the material chamber. The piston extends to push the material into the fluid conduit. The syringe assembly includes a diverter fluidly connected to the base fluid chamber and moveable between first and second positions. The first position of the diverter fluidly connects the base fluid chamber to a base fluid reservoir of the hydraulic fracturing system and fluidly disconnects the base fluid chamber from an outlet of a frac pump of the hydraulic fracturing system. The second position of the diverter fluidly connects the base fluid chamber to the outlet of the frac pump and fluidly disconnects the base fluid chamber from the base fluid reservoir.

A material dispensing system can comprise a first and second supply container housing a first and second material, respectively, comprising a first and second fluid, respectively; a first and second metering cylinder fluidly connected to the first and second supply container, respectively, the second metering cylinder configured to move from a first to a second stroke position in unison with the first metering cylinder; a dispensing head configured to receive a first and second liquid of the first and second fluids, respectively; a first recycling valve positioned between the first metering cylinder and the dispensing head; and a second recycling valve positioned between the second metering cylinder and the dispensing head, the first and second recirculating valves configured to draw a portion of the first and second fluids back into the first and second supply containers, respectively, in an open position.

A syringe assembly for a hydraulic fracturing system includes a syringe having a material chamber, a base fluid chamber, and a piston. The material chamber is configured to be fluidly connected to a fluid conduit. The piston retracts to draw material into the material chamber. The piston extends to push the material into the fluid conduit. The syringe assembly includes a diverter fluidly connected to the base fluid chamber and moveable between first and second positions. The first position of the diverter fluidly connects the base fluid chamber to a base fluid reservoir of the hydraulic fracturing system and fluidly disconnects the base fluid chamber from an outlet of a frac pump of the hydraulic fracturing system. The second position of the diverter fluidly connects the base fluid chamber to the outlet of the frac pump and fluidly disconnects the base fluid chamber from the base fluid reservoir.

A material dispensing system can comprise a first and second supply container housing a first and second material, respectively, comprising a first and second fluid, respectively; a first and second metering cylinder fluidly connected to the first and second supply container, respectively, the second metering cylinder configured to move from a first to a second stroke position in unison with the first metering cylinder; a dispensing head configured to receive a first and second liquid of the first and second fluids, respectively; a first recycling valve positioned between the first metering cylinder and the dispensing head; and a second recycling valve positioned between the second metering cylinder and the dispensing head, the first and second recirculating valves configured to draw a portion of the first and second fluids back into the first and second supply containers, respectively, in an open position.

A base valve, a base pump, a catalyst valve, a catalyst pump, a mixing chamber, a base cylinder connected to the base valve, and a catalyst cylinder connected to the catalyst valve. The base and catalyst cylinders are actuated so as to push base and catalyst fluids out of the base and catalyst cylinders, respectively, and into the mixing chamber. An electronic controller has a ready mode and a dispensing mode. In the ready mode, the controller i) activates the base and catalyst pumps and ii) signals the actuator to push or pull, in response to a dispense signal being asserted. In the dispensing mode, the controller a) deactivates the base and catalyst pumps, b) signals the actuator to stop pushing or stop pulling, and maintains a) and b) in response to the dispense signal being de-asserted. Other embodiments are also described.