Method of controlling the concentration and stability of an emulsion

A method of controlling the stability of an oil-in-water emulsion suitable for use as a lubricant in a metalworking operation comprising the steps of,

• providing a measuring cell including a U-shaped tube mounted in a substantially vertical direction with the open end of the "U" being rigidly supported and the closed loop end unsupported,
• flowing a portion of the emulsion through the U-shaped tube,
• determining the density of the emulsion flowing through the U-shaped tube by exciting the unsupported end of the tube at a constant frequency and generating a first electric signal which is a function of the tube displacement,
• periodically interrupting the flow of the emulsion through the cell and maintaining a quantity of the emulsion in the cell in a quiescent state for a predetermined time sufficient to permit the oil and water phases of the emulsion in the U-shaped tube to at least partially separate,
• operating the cell to determine the density of the emulsion in the cell at the termination of the predetermined time and to generate a second electric signal proportional to the determined density of the at least partially separated emulsion, and
• comparing the first and second electric signals to determine the change of density of the liquid in the cell during the predetermined time and utilizing the determined change of density as an indication of emulsion stability.

A method of controlling the oil concentration in an oil-in-water emulsion suitable for use as a lubricant in a metalworking operation comprising, the steps of

• circulating a portion of the emulsion through a liquid density measuring cell and operating the cell to generate a first electric signal proportional to the density of the emulsion flowing through the cell,
• conducting the first electric signal to a continuous recorder and operating the recorder to provide a continuous record of the measured density and to compare the measured density with a predetermined desired density,
• generating a second electric signal in response to the detection of a predetermined minimum deviation between the measured density the desired density, and
• utilizing said second electric signal to control the addition of make-up oil to the emulsion to automatically maintain the oil concentration of the emulsion within predetermined limits
• periodically interrupting the flow of emulsion through the cell while maintaining a quantity of the emulsion in the cell for a predetermined time sufficient to permit the oil and water phases of the emulsion to at least partially separate
• comparing the density of the emulsion in the cell at the beginning and end of the predetermined times to determine the density change due to separation of the oil and water phases, and
• utilizing the determined density change as an indication of emulsion stability.