High pressure intensifiers

1. A hydraulic intensifier comprising:

a first piston reciprocable in a first cylinder;

a second piston reciprocable in a second cylinder;

a cylindrical member configured to join the pistons so that each piston has a first face which has a greater surface area than its second, opposite face as a result of said cylindrical member, wherein the first face of each of the pistons is located at a respective low pressure side and the second face of each of the pistons is located at a respective high pressure side;

a first input and a second input configured to supply low pressure hydraulic fluid to respective low pressure sides;

an output configured to transport high pressure hydraulic fluid from the high pressure sides;

a first solenoid operated pilot valve and a second solenoid operated pilot valve configured to control the supply of low pressure hydraulic fluid to respective ones of the inputs; and

an electronic operator configured to operate the solenoid operated pilot valves configured to supply low pressure hydraulic fluid,

wherein the cylindrical member is located between the first and second pistons whereby, if the low pressure fluid is applied to one of said low pressure sides, said low pressure fluid also flows from said low pressure side through the cylindrical member to the high pressure side of the other piston, wherein said cylindrical member comprises a first passageway between the low pressure side of the first piston and the high pressure side of the second piston, and a second passageway between the low pressure side of the second piston and the high pressure side of the first piston, wherein each of the passageways is provided with a respective non-return valve configured to permit flow from the low pressure side to the high pressure side.

2. An intensifier according to claim 1 , wherein said electronic operator is provided by a subsea electronics module of a subsea well control system.

3. A method of producing high pressure hydraulic fluid comprising:

providing a hydraulic intensifier comprising:

a first piston reciprocable in a first cylinder;

a second piston reciprocable in a second cylinder; and

a cylindrical member configured to join the pistons so that each piston has a first face which has a greater surface area than its second, opposite face as a result of said cylindrical member, wherein the first face of each of the pistons is located at a respective low pressure side and the second face of each of the pistons is located at a respective high pressure side, and wherein said cylindrical member comprises a first passageway, between the low pressure side of the first piston and the high pressure side of the second piston, and a second passageway, between the low pressure side of the second piston and the high pressure side of the first piston, each of the passageways being provided with a respective non-return valve configured to permit flow from the low pressure side to the high pressure side;

supplying low pressure hydraulic fluid to respective low pressure sides using a first input and a second input;

transporting high pressure hydraulic fluid from the high pressure sides using an output;

controlling the supply of said low pressure hydraulic fluid to each input using a first solenoid operated pilot valve and a second solenoid operated pilot valve; and

supplying low pressure hydraulic fluid using an electronic operator configured to operate the pilot valves,

wherein if low pressure fluid is applied to one of said low pressure sides, said cylindrical member applies fluid to the high pressure side of the other piston.

4. A method according to claim 3 , wherein said electronic operator is provided by a subsea electronics module of a subsea well control system.

5. A method according to claim 3 , further comprising

alternately energizing and de-energizing the first solenoid pilot valve and/or the second solenoid pilot valve using the electronic operator.

6. A method according to claim 3 , wherein

the output is coupled with each of said high pressure sides.