The Sentinel ultrasonic flowmeter is designed to meet the high-accuracy requirements of AGA9 for natural gas custody transfer, as well as the NMI pattern approval.
A Sentinel meter body is composed of a length of carbon steel pipe with flanged ends, rated to the pressure requirements of the individual installation and two pairs of pre-installed ultrasonic transducers. The system is factory assembled and tested to ensure that it meets strict quality control standards.
Advanced Ultrasonic Transducer Technology -High Power for High Velocity
The heart of ultrasonic measurement is the transducer. The Sentinel T11 transducer is specifically designed for natural gas applications. The transducers provide high transmission power through the gas, ensuring optimal performance under high flow conditions of up to 118 ft/sec (36 m/s). The robust all-welded metal design ensures resistance to corrosion and pressure cycling.
The transducer frequency is matched to the pipe size of the system ordered. In addition, the Sentinel transducer holder includes unique acoustic isolation characteristics that allow optimal performance, even in noisy applications such as wet natural gas.
How Correlation Transit-Time™ Measurement Works
Ultrasonic transducers are installed in the meter body, one upstream of the other. The transducers send and receive ultrasonic pulses through the fluid. The meter measures the difference between the upstream and downstream transit times, and uses digital signal processing and correlation detection to calculate velocity and volumetric flow rate.
A complete Sentinel system consists of the ultrasonic meter, flow conditioner, and upstream / downstream piping. This confi guration removes the uncertainty associated with installation effects (distorted flow profi le caused by valves, elbows, other piping system components) on the overall meter performance. This solution provides a simplified, yet cost effective metering system without exposing the user to any additional risk in measurement uncertainty. Customers can be assured of accurate flow measurements because flow profile, a major source of uncertainty if not fully developed and uniform, is removed from the overall equation in the ultrasonic flowmeter system.
The Sentinel path configuration is designed such that a minimum number of paths interrogates the maximum area of the pipe, resulting in measurement stability and superb repeatability. In addition, the meter uses no bounced or multiple bounced paths susceptible to signal distortion from build-up on walls and adversely affected by ultrasonic noise (often from upstream piping and valving) and high flow velocity. The straight single path provides a solid measurement and maximizes the long term performance of the meter.
The Sentinel flow metering system operates with a better than 5 Hz response rate, depending on pipe size, using a sophisticated multi-mode signal processing technique that delivers accurate and dependable meter performance with high turndown. This fast sampling ensures that system accurately measures flow under dynamic and pulsating flow conditions.
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