Subsea multipiston pump module and subsea multistage pump

1. A subsea multipiston pump for closing a hydraulic ram of a blowout preventer, comprising:

at least a first and a second piston, oscillatingly arranged to pump a media fluid from a source to a target,

the first and the second pistons being driven either in a parallel mode oscillating in phase with each other, or in a serial mode oscillating out of phase with each other; and

at least one piston connection device for fluidly connecting the two pistons in a controllable manner, so that in parallel mode the first and the second pistons are pumping the media fluid in parallel, and in serial mode, the first and the second pistons are pumping the media fluid in serial.

2. The subsea multipiston pump according to claim 1 ,

wherein the first and the second pistons are arranged within a common housing.

3. The subsea multipiston pump according to claim 1 , wherein the first and the second pistons comprise at least two piston heads oscillating forth and back in respective piston chambers for pumping the media fluid.

4. The subsea multipiston pump according to claim 1 , wherein the first and the second pistons are fluidly connected with a suction manifold for suction of the media fluid and with a discharged manifold for discharge of the media fluid.

5. The subsea multipiston pump according to claim 4 , wherein the suction manifold of the first and the second pistons comprises at least one check valve and/or the discharge manifold of the first and the second pistons comprises at least one check valve.

6. The subsea multipiston pump according to claim 1 , wherein the first and the second pistons are hydraulic pistons driven by a drive fluid supplied from a remotely operated vehicle.

7. The subsea multipiston pump according to claim 1 , wherein a controller directs a drive fluid to the first and the second pistons in a time controlled manner for oscillating the first and the second pistons for individually controlling the phase of the first and the second.

8. The subsea multipiston pump according to claim 1 , wherein a controller is arranged to switch the fluid flow of the driving fluid between at least two hydraulic piston chambers of at least one piston of the first or the second pistons, for changing the oscillation phase of the respective piston dependent on the fluid pressure of the media fluid.

9. The subsea multipiston pump according to claim 1 , wherein a controller for driving the first and the second pistons is remotely controllable and electronically controllable.

10. The subsea multipiston pump according to claim 1 , wherein a controller comprises at least one electronically controllable valve and at least one solenoid and/or servo valve provided in a drive fluid manifold of the first and the second pistons.

11. The subsea multipiston pump according to claim 1 , wherein a controller comprises a sensor for detecting a pressure level of the media fluid.

12. The subsea multipiston pump according to claim 11 , wherein the sensor is arranged on an output side and in a discharge manifold of the first and the second pistons.

13. The subsea multipiston pump according to claim 1 , wherein, a controller is arranged to automatically change from parallel mode to serial mode and/or vice versa, when a defined pressure threshold in the media fluid and in a discharge manifold of the first and the second pistons is detected.

14. The subsea multipiston pump according to claim 1 , wherein, the piston connection device comprises a cross feeding valve.

15. The subsea multipiston pump according to claim 14 , wherein the cross feeding valve comprises at least one valve and a check valve.

16. The subsea multipiston pump according to claim 15 , wherein, the at least one valve and the check valve are arranged to establishes a fluid connection between the first and the second piston.

17. The subsea multipiston pump according to claim 14 , wherein the cross feeding valve comprises at least one valve arranged within the piston connection device and in at least one fluid connection between a piston chamber of the first piston and a piston chamber of the second piston.

18. The subsea multipiston pump according to claim 14 , wherein the cross feeding valve comprises at least one valve arranged that in the serial mode an output of a near side piston head of the first piston is directed to an input of a far side piston head of the second piston, so that a media fluid pressure outputted from the first piston is an additive to a drive fluid pressure of the second piston or vice versa.

19. The subsea multipiston pump according to claim 14 , wherein the cross feeding valve is remotely and electronically controllable.

20. The subsea multipiston pump according to claim 1 , further comprising an additional subsea multipiston pump comprising a third and a fourth piston and the additional multipiston pump being fluidly connected with the subsea multipiston pump.

21. The subsea multipiston pump according to claim 20 , wherein the additional subsea multipiston pump is fluidly connected with the subsea multipiston pump in parallel.

22. An intervention skid for attachment to a remotely operated vehicle, the intervention skid comprising:

at least one multipiston pump comprising:

at least a first and a second piston, oscillatingly arranged to pump a media fluid from a source to a target,

the first and the second pistons being driven either in a parallel mode, where they are oscillating in phase with each other, or in a serial mode, where they are oscillating out of phase with each other; and

at least one piston connection device for fluidly connecting the two pistons in a controllable manner, so that in parallel mode the first and the second pistons are pumping the media fluid in parallel, and in serial mode, the first and the second piston are pumping the media fluid in serial.

23. A method of pumping a media fluid under subsea conditions from a source to a target, the method comprising:

pumping the media fluid via a multipiston pump, the multipiston pump comprising at least a first and a second reciprocating piston, oscillatingly arranged to pump a media fluid from a source to a target; and

controlling first and the second pistons being either driven in a parallel mode in phase with each other, or in a serial mode out of phase with each other wherein the first and the second pistons are connected with each other by at least one piston connection device so that in the parallel mode the first and the second pistons are pumping the media fluid in parallel, and in the serial mode, the first and the second pistons are pumping the media fluid in serial.

24. The subsea multipiston pump according to claim 1 , wherein the serial mode oscillating out of phase between the first piston and second piston is by half a cycle.