Buoyancy force sensor for a hydrometer and interlock for a storage tank used in containing a respirable liquid cryogen

摘要

A sensor for sensing buoyancy force within a liquid mixture stored within a storage tank and an interlock employing the sensor to prevent a respirable cryogenic mixture from being dispensed from the storage tank with an unsafe oxygen content. The sensor has a float adapted to be submerged in the liquid mixture, thereby to exert a buoyancy force referable to the density. The buoyancy force is sensed by a load cell connected to an elongated base element cantilevered from the outlet by a bracket. The mounting of such sensor ensures that the buoyancy force and therefore, the density of the liquid as dispensed will be measured as opposed to liquid density at some other location of the tank. Such sensor can serve in an interlock in which a controller responsive to the load cell and a temperature sensor, also located within the outlet, controls a valve to close the outlet when the mixture has an unsafe oxygen level.