Process and apparatus for electronic control of the transfer and delivery of high purity chemicals

A process for control of apparatus for transfer and delivery of chemical from at least one bulk source to at least one end-use station which comprises:

• providing multiple vessels, each such vessel including valving to control flow of chemical into and out of the vessel;
• providing at least one conduit for the flow of chemical between the bulk source and each such vessel;
• providing at least one conduit for the flow of chemical between each such vessel and an end-use station;
• providing means to transfer chemical at a uniform flow rate from a bulk source to each such vessel;
• providing means to pressurize each such vessel, including valving to control the flow of pressurized gas into each vessel;
• providing means to sense level of chemical in each such vessel and to provide a signal therefor;
• providing means to sense demand for chemical at an end-use station and to provide a signal therefor;
• providing electronic means to analyze the signals from each of the means to sense the presence of chemical in each vessel and the means to sense demand at an end-use station and to regulate the operation of the valving in response thereto;
• controlling chemical flow through each vessel through the steps comprising:
• when low chemical level is sensed in a vessel, the electronic means regulates the valving so as to cause chemical to be transferred from a bulk source into the vessel until a high chemical level is sensed;
• when a high chemical level is sensed in a vessel, the electronic means regulates the valving so as to cause the vessel to be pressurized;
• and when a demand is sensed at an end-use station, the electronic means regulates the valving to cause chemical to be delivered under pressure from the vessel to the end-use station;
• and
• maintaining uniform flow rate of chemical through the system through the steps comprising:
• when a low chemical level is sensed in a first vessel delivering chemical, the electronic means regulates the valving to cause chemical to be delivered from a second vessel before the first vessel is completely evacuated, so as to assure no interruption in flow.