Erosion resistant flow conduit

1. A flow directing apparatus for conveying a fluid flow having a process pressure, the apparatus comprising:

a housing forming a pressure boundary;

a flow directing insert fit sealably and wholly within the housing for forming a pressure chamber about the insert and between the insert and the housing, the insert having an inlet end for receiving the fluid flow and a discharge end for discharging the fluid flow,

wherein the pressure chamber comprises pad fluid at a pad pressure, and the pad pressure is controlled such that the differential between the pad pressure and the process pressure limits the magnitude of pressure-induced stress in the insert;

a pressure source in fluid communication with the pressure chamber;

a pressure monitor for monitoring the pressure differential between the process pressure and pad pressure; and

a regulator controlling the pressure source for maintaining the pad pressure relative to the process pressure in response to the process pressure monitored by the pressure monitor.

2. The flow directing apparatus of claim 1 wherein the insert is replaceable.

3. The flow directing apparatus of claim 1 wherein:

the inlet end is sealed to the housing at an inlet seal; and

the discharge end is sealed to the housing at a discharge seal.

4. The flow directing apparatus of claim 1 wherein:

the fluid flow contains particulates; and

the insert is a wear resistant material resistive to erosion from the particulates.

5. The flow directing apparatus of claim 4 wherein the wear resistant material is a non-ductile or brittle material.

6. The flow directing apparatus of claim 5 wherein the wear resistant material is a ceramic.

7. The flow directing apparatus of claim 1 wherein

said regulator introduces a pressure from the pressure source as necessary, in response to the pressure differential monitored by the pressure monitor, so as to maintain the pressure differential between the fluid flow and the pressure chamber.

8. The flow directing apparatus of claim 1 wherein the pressure chamber contains a fluid pad of liquid.

9. The flow directing apparatus of claim 8 wherein the pressure source contains gas, and wherein the regulator comprises:

an isolation chamber fluidly connected between the pressure source and the fluid pad, the isolation chamber forming a cylinder and having a piston movable therein, the piston being positioned intermediate the pressure source and the fluid pad of liquid.

10. The flow directing apparatus of claim 8 wherein:

an isolation chamber forms a stepped cylinder having a stepped piston moveable therein; wherein

the piston has a first smaller area in fluid communication with the fluid flow for receiving the process pressure and a larger second area in fluid communication with the liquid of the fluid pad for automatically maintaining the pad pressure at a pressure lower than the process pressure.

11. An erosion resistant flow conduit comprising:

a wellhead piping;

a flow bend in said wellhead piping, said flow bend comprising the flow directing apparatus of claim 1 .

12. The flow directing apparatus of claim 1 wherein the housing comprises:

a body having at least a first sealable opening thereon; and

at least a first port body having an opening thereon, said first port body fitting to the first opening for forming a first port and for securing and sealably fitting the discharge end of the insert to the first port.

13. The flow directing apparatus of claim 12 wherein said body further has a second sealable opening thereon, and wherein said housing further comprises:

a second port body having an opening thereon, said second port body fitting to the second opening for forming a second port and for securing and sealably fitting the inlet end of the insert to the second port; the housing forming a pressure boundary between the first and second ports and the insert being fit sealably within the housing between the first and second ports.

14. The flow directing apparatus of claim 13 wherein said housing further comprises:

a third sealable opening on the body for accessing the insert.

15. The flow directing apparatus of claim 14 wherein said housing further comprises a third port body securing and sealably fitting the third opening.

16. The flow directing apparatus of claim 13 wherein:

the first port is an outlet port;

the second port is an inlet port; and

fluid flow from the inlet port flows to the first end of the insert and the outlet port receives fluid flow from the second end of the insert.

17. The flow directing apparatus of claim 13 wherein the discharge end of the insert is secured and sealably fit to the first port body.

18. The flow directing apparatus of claim 17 wherein the discharge end of the insert further comprises a flange for securing and sealably fitting to the first port body.

19. The flow directing apparatus of claim 18 wherein the flange of the discharge end of the insert is sealably secured to the first port body using a ring seal and a retainer ring.

20. The flow directing apparatus of claim 19 wherein said retainer ring comprises two or more sectional pieces for arrangement about the insert.

21. The flow directing apparatus of claim 17 wherein

the inlet end of the insert is secured and sealably fit to the second port body.

22. The flow directing apparatus of claim 21 wherein the inlet end of the insert further comprises a flange for securing and sealably fitting to the second port body.

23. The flow directing apparatus of claim 22 wherein the flange of the inlet end of the insert is sealably secured to the second port body using a ring seal and a retainer ring.

24. The flow directing apparatus of claim 23 wherein said retainer ring comprises two or more sectional pieces for arrangement about the insert.