The present invention relates to a subsea multipiston pump module, a subsea multistage pump and skid, having two reciprocating pistons controlled by a control means in such a way that the pistons can be driven either in a parallel mode, where the pistons are driven in phase with each other, or in a serial mode, where the pistons are driven out of phase with each other, wherein the pistons are fluidly connected with each other by a piston connection means in such a way that in parallel mode they are fluidly connected in parallel, and in serial mode, they are fluidly connected in serial. Further, the invention relates to a method of pumping a media fluid under subsea conditions.

The present invention concerns a diaphragm pump comprising a delivery chamber separated from a hydraulic chamber by way of a diaphragm, wherein the delivery chamber is respectively connected to a suction connection and a pressure connection and the hydraulic chamber which can be filled with a working fluid can be acted upon with a pulsating working fluid pressure and the diaphragm can be reciprocated between a pressure position in which the volume of the delivery chamber is smaller and a suction position in which the volume of the delivery chamber is larger. In that arrangement the hydraulic chamber is connected to a working fluid supply by way of a leak replenishment valve, wherein the leak replenishment valve is so designed that when the pressure in the hydraulic chamber in the suction position of the diaphragm is less than a predetermined minimum value p.sub.Min the leak replenishment valve opens and the hydraulic chamber has an outlet passage which is closed by a pressure limiting valve which is so designed that if the pressure in the hydraulic chamber rises above a predetermined maximum value p.sub.Max the pressure limiting valve opens and working fluid can leave the hydraulic chamber by way of the outlet valve. To provide a corresponding diaphragm pump which automatically reduces the metering power in the overpressure situation without the use of additional sensors being necessary it is proposed according to the invention that the working fluid supply is arranged in a first and in a second chamber, the two chambers being connected together by way of a first connecting passage.

The present invention relates to a subsea multipiston pump module, a subsea multistage pump and skid, having two reciprocating pistons controlled by a control means in such a way that the pistons can be driven either in a parallel mode, where the pistons are driven in phase with each other, or in a serial mode, where the pistons are driven out of phase with each other, wherein the pistons are fluidly connected with each other by a piston connection means in such a way that in parallel mode they are fluidly connected in parallel, and in serial mode, they are fluidly connected in serial. Further, the invention relates to a method of pumping a media fluid under subsea conditions.

The present invention concerns a diaphragm pump comprising a delivery chamber separated from a hydraulic chamber by way of a diaphragm, wherein the delivery chamber is respectively connected to a suction connection and a pressure connection and the hydraulic chamber which can be filled with a working fluid can be acted upon with a pulsating working fluid pressure and the diaphragm can be reciprocated between a pressure position in which the volume of the delivery chamber is smaller and a suction position in which the volume of the delivery chamber is larger. In that arrangement the hydraulic chamber is connected to a working fluid supply by way of a leak replenishment valve, wherein the leak replenishment valve is so designed that when the pressure in the hydraulic chamber in the suction position of the diaphragm is less than a predetermined minimum value p.sub.Min the leak replenishment valve opens and the hydraulic chamber has an outlet passage which is closed by a pressure limiting valve which is so designed that if the pressure in the hydraulic chamber rises above a predetermined maximum value p.sub.Max the pressure limiting valve opens and working fluid can leave the hydraulic chamber by way of the outlet valve. To provide a corresponding diaphragm pump which automatically reduces the metering power in the overpressure situation without the use of additional sensors being necessary it is proposed according to the invention that the working fluid supply is arranged in a first and in a second chamber, the two chambers being connected together by way of a first connecting passage.