Multi-phase pumping system with self-purging filtration
An apparatus and method prevent entrained solids from entering a pump by directing a process stream through an active upstream filter that removes the solids, and then through a downstream idle filter where the process stream purges the filter of previously retained solids. The flow path is periodically switched to exchange the roles of the filters, so that none of the filters is saturated, and the solids remain in the process flow but bypass the pump. Any need for a low pressure destination for purged solids and purging fluid and/or any environmental impact of dumping process fluid and solids into the environment is thereby avoided. Partially opened valves can be used to divert only part of the downstream flow for filter purging. Selectable paths can be included for which no filters are purged. The downstream flow can be divided and used to simultaneously purge a plurality of idle filters.
1. A system for protecting a pump from solids entrained in a process flow, the system comprising:
a pump in fluid communication with a first filter, a second filter, and a plurality of valves, said valves being automatically controlled by a controller;
an inlet through which the process flow enters the system from an upstream source; and
an outlet through which the process flow emerges from the system toward a downstream destination;
said controller being configured to control said valves so as to select between at least two selectable flow paths, wherein each of said flow paths directs the process flow from the inlet to one of the plurality of filters, where the entrained solids are retained and removed from the process flow, said process flow being directed from thence through the pump, and at least part of the process flow being directed from thence to a another of the plurality of filters, where previously retained solids are purged and carried by the process flow toward the downstream destination;
said controller being configured to switch between said flow paths so as to remove the entrained solids from the process flow upstream of the pump, and then reinject the entrained solids into the process flow downstream of the pump, thereby directing all of the process flow and entrained solids to the outlet while ensuring that the entrained solids do not enter the pump, and preventing any of said filters from becoming saturated by the retained solids.
2. The system of claim 1 , wherein said selectable flow paths further comprise a flow path that directs the process flow from the pump to the outlet without purging any of the filters.
3. The system of claim 1 , wherein at least one of the valves can be partially opened by the controller.
4. The system of claim 1 , wherein, after flowing through the pump, the process flow is divided into a plurality of flow streams, at least one of the flow streams being directed so as to purge one of the filters.
5. The system of claim 4 , wherein at least one of the flow streams is directed from the pump to the outlet without purging a filter.
6. The system of claim 4 , wherein a plurality of the flow streams are directed so as to purge a plurality of the filters.
7. The system of claim 1 , wherein the pump is a multiphase pump.
8. The system of claim 7 , wherein the multiphase pump is a twin screw multiphase pump.
9. The system of claim 1 , wherein the entrained solids include sand.
10. The system of claim 1 , further comprising a mechanism in communication with the controller for determining quantities of entrained solids retained by each of the filters.
11. A method for protecting a pump from solids entrained in a process flow, the method comprising:
providing a pumping system comprising an inlet through which the process flow enters the system from an upstream source, and an outlet through which the process flow emerges from the system toward a downstream destination, said pumping system further including a pump in fluid communication with a first filter, a second filter, and a plurality of valves, said valves being automatically controlled by a controller so as to select between selectable flow paths from said inlet to said outlet;
directing said process flow through a first of said selectable flow paths, in which the entrained solids are removed from the process flow and retained by the first filter upstream of the pump, and at least part of the process flow purges previously retained solids from the second filter downstream of the pump;
directing said process flow through a second of said selectable flow paths, in which the entrained solids are removed from the process flow and retained by the second filter or by a third filter upstream of the pump, and at least part of the process flow purges retained solids from the first filter downstream of the pump; and
continuing to select between said selectable flow paths so as to remove the entrained solids from the process flow upstream of the pump, and then reinject the entrained solids into the process flow downstream of the pump, thereby directing all of the process flow and entrained solids to the outlet, while ensuring that the entrained solids do not enter the pump, and preventing any of the filters from being saturated by the entrained solids.
12. The method of claim 11 , wherein said selectable flow paths further comprise a flow path that directs the process flow from the pump to the outlet without purging any of the filters.
13. The method of claim 11 , wherein at least one of the valves can be partially opened by the controller.
14. The method of claim 11 , wherein after flowing through the pump, the process flow is divided into a plurality of flow streams, at least one of the flow streams being directed so as to purge one of the filters.
15. The method of claim 14 , wherein at least one of the flow streams is directed from the pump to the outlet without purging a filter.
16. The method of claim 14 , wherein a plurality of the flow streams are directed so as to purge a plurality of the filters.
17. The method of claim 11 , wherein the pump is a multiphase pump.
18. The method of claim 17 , wherein the multiphase pump is a twin screw multiphase pump.
19. The method of claim 11 , wherein the entrained solids include sand.
20. The method of claim 11 , wherein the controller is configured to select flow paths at least partly based on determined quantities of entrained solids retained by each of the filters.