Regulating pressure
July 1st 2008

The Diamond Light Source synchrotron in Didcot, Oxfordshire, is a 'super microscope' that enables scientists to see microscopic structures in great detail using X-rays, ultraviolet and infrared beams. The machine covers an area equivalent to five football pitches and within it are three accelerators, which can generate intense light beams 10 billion times brighter than the sun.

Applying a magnetic field to electrons forces them to bend and follow the path of a giant storage ring and in the process, they emit synchrotron light that the scientists use to carry out their research. Over 450 magnets are used to generate the magnetic field required to drive the electrons around the ring. A significant amount of heat is generated by the magnets, necessitating cooling to prevent overheating. The cooling is achieved using processed ionised water, pumped around the site by large pumps delivering over 200L/sec at pump heads of up to 10 bar. Each magnet must be supplied with the correct amount of cooling water at a differential pressure which will not cause damage.

Samson had to provide selfoperated differential pressure regulators, which could pass high flow rates and control differential pressure to high accuracy. However, as self-operated valves are proportional controllers they exhibit a degree of offset. This is not important in most applications, but for the Diamond Light Source project, the typical offset would not be acceptable. Pilot and non-pilot valves were selected to suit Diamond's flow/pressure tolerances. For the high accuracy circuits, Samson provided special type 2333 pilot operated valves made in stainless steel to suit the processed ionised water application, and more standard (but still all stainless) type 42-24 and 42- 25 differential pressure regulators for the less demanding circuits.

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