L'air Liquide

Jean Arnault

Francis Cuny

Hugues Vermeille

Process for controlling the flow of a fluid through a valve having a given section and a movable valve member, in which the pressures of the fluid which are upstream P.sub.upstream and downstream P.sub.downstream of the valve and the position d of the valve member are measured, then the real flow Q.sub.real of the fluid is calculated and compared with a set value Q.sub.0, the difference signal Q.sub.real -Q.sub.0 commanding the displacement of the valve member in the desired direction, said process comprising effecting the real flow calculation by measuring the ratio R=P.sub.upstream /P.sub.downstream which is compared with a predetermined value R and calculating the product Q.sub.sonic =k.times.P.sub.upstream .times.d so that when R&gt;R.sub.0, the product Q.sub.sonic is directly compared with a set value Q.sub.0, the difference signal Q.sub.sonic -Q.sub.0 commanding the displacement of the valve member in the desired direction whereas, when R&lt;R.sub.0, the ratio R is converted into a digital signal whose value corresponds to the address of a memory whose content is converted into an analog correction signal which, after multiplication by Q.sub.sonic, represents a value proportional to the flow Q.sub.subsonic of the fluid at the subsonic rate, this value Q.sub.subsonic being then compared with the set value Q.sub.0, the signal Q.sub.subsonic -Q.sub.0 commanding the displacement of the valve member in the desired direction.

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Saint Nazaire les Eymes, France

Jean Arnault