Patent ID: 7389786

Claim:
A system for odorizing natural gas flowing through a pipeline by injecting odorant into the pipeline at a controlled rate, comprising: an odorant storage tank containing an odorant to be injected; a pressurized source of inert gas communicating with the odorant storage tank for maintaining the tank at a desired positive pressure above the pressure of the pipeline; an injection conduit communicating the odorant storage tank with the pipeline; a metering valve located within the injection conduit for metering chemical to be injected into the pipeline, the metering valve being adjustable between a drop wise setting for metering chemical into the pipeline on a drop by drop basis and a steady flow setting for metering chemical on a steady state flow basis; an ultrasonic measuring unit associated with the metering valve for measuring flow passing through the metering valve and into the pipeline, the ultrasonic measuring unit including one or more pairs of ultrasonic transmitters and ultrasonic receivers which act as either proximity sensors or by measuring transit time to provide a measurement of the flow rate of odorant on either a drop by drop basis or in a steady state flow condition; and wherein an injection chamber receives odorant passing from the odorant storage tank and wherein natural gas from the pipeline flows to and from the injection chamber to provide a pressure head on the odorant in the injection chamber.