Abstract: A fluid pressure control system comprising a first chamber, the pressure in which is to be controlled, a second chamber and a valve means for controlling communication between the first and second chambers. A controller is arranged such that, if the pressure in the first chamber differs from a required pressure, the controller i) operates the valve means to close off communication between the first and second chambers, ii) varies the pressure in the second chamber, iii) opens communication between the first and second chambers to deliver a discrete pressure step to the first chamber, and, iv) repeats i) to iii) until the pressure in the first chamber reaches a required level.

Abstract: A liquid delivery system which can deliver liquid from a pressurized vessel holding a volume of the liquid, out through an outlet under a controlled pressure, thereby controlling the delivery rate of the liquid. The vessel can be re-filled while controlled liquid delivery continues, either by re-filling directly into the vessel and allowing any excess of pressure to be relieved, or by using a second pressurized vessel and continuing delivery from one vessel while the other is re-filled.