Method and apparatus for monitoring particle laden pneumatic abrasive flow in an abrasive fluid jet cutting system

1. A particle conveyor, comprising:

a particle inlet port;

a particle outlet port configured to be drawn to a partial vacuum;

a particle supply tube configured to pneumatically convey particles from the particle inlet port to the particle outlet port, the particle supply tube including at least two measurement ports at different distances along the particle supply tube having no flow constriction between the at least two measurement ports;

a liquid jet nozzle including a mixing tube configured to entrain the particles from the outlet port in a high velocity liquid jet;

a differential pressure transducer coupled to the at least two measurement ports and configured to measure a differential pneumatic pressure between the at least two measurement ports; and

a controller operatively coupled to the differential pressure transducer and configured to determine one or more particle flow parameters responsive to the differential pneumatic pressure.

2. The particle conveyor of claim 1 , wherein the particle conveyor comprises an abrasive supply system for an abrasive jet cutting system and the particles are abrasive particles; and wherein the mixing tube is configured to draw the partial vacuum and entrain the abrasive particles in a high velocity liquid jet in response to the liquid jet nozzle being pressurized.

3. The particle conveyor of claim 1 , wherein the particle inlet port is held substantially at atmospheric pressure.

4. The particle conveyor of claim 1 , further comprising:

a fitting forming a portion of the particle delivery tube, the fitting including a wall defining an entrained particle flow channel, and having at least two measurement ports separated by a length along the entrained particle flow channel; and

wherein the differential pressure transducer is operatively coupled to the at least two measurement ports.

5. The particle conveyor of claim 4 , wherein a differential pressure between the at least two measurement ports is proportional to a pressure drop caused by flow of air around and past entrained particles in the entrained particle flow channel between the at least two measurement ports.

6. The particle conveyor of claim 4 , wherein the at least two measurement ports are at non-right angles relative to the entrained particle flow channel to reduce or eliminate particles entering the measurement ports.

7. The particle conveyor of claim 1 , wherein the differential pressure transducer comprises:

two or more absolute or gauge pressure transducers operatively coupled to respective measurement ports.

8. The particle conveyor of claim 1 , wherein the controller is configured to operate using electrical, pneumatic, or electrical and pneumatic control logic.

9. The particle conveyor of claim 1 , wherein the one or more particle flow parameters includes one or more of nominal particle flow, a low concentration of entrained particles, or a blockage in particle flow.

10. The particle conveyor of claim 1 , wherein the particle conveyor comprises an abrasive supply system for an abrasive jet cutting system and the particles are abrasive particles;

wherein the controller is configured to control at least one selected from the group consisting of a supply of liquid to the liquid jet nozzle, movement of the liquid jet nozzle, operation of the abrasive supply system, and providing an alarm responsive to determining the one or more particle flow parameters.

11. The particle conveyor of claim 10 , wherein the controller is configured to ignore the differential pneumatic pressure or apply a different response to the differential pneumatic pressure during start-up.

12. The particle conveyor of claim 11 , wherein the controller is configured to respond if one or more of the differential pneumatic pressure signal indicates a decrease in differential pneumatic pressure below a low pressure value or the differential pneumatic pressure signal indicates an increase in differential pneumatic pressure above a high pressure value.

13. The particle conveyor of claim 12 , wherein the differential pneumatic pressure value or values is determined at least in part responsive to one or more previously measured differential pneumatic pressures.