DigitalFlow GC868 Ultrasonic Gas Flow Meter

 

The Panametrics DigitalFlow GC868 ultrasonic gas flow meter is a fixed-installation clamp-on. It has advanced clamp-on ultrasonic transducers, a clamping fixture, and a preamplifier connected by cables to the transducers and to the GC868 electronics. The DigitalFlow GC868 flow meter can be used to measure the flow of any gas.

Features and Benefits

 

• Clamp-on unobstructed installation

• No wetted parts

• Two-channel/two-path version available

• No moving parts

• No pressure drop

• Sound speed output

• Simple installation

• Standard volumetric flow calculation

• Steam mass flow

• Supercompressibility compensation

• Suitable for a wide range of temperatures and pressures

Applications

 

The DigitalFlow GC868 clamp-on gas flowmeter is a complete ultrasonic flow metering system for measurement of most gases, including:

 

• Natural gas

• Compressed air

• Fuel gases

• Erosive gases

• Corrosive gases

• Toxic gases

• High-purity gases

• Air separation gases

• Steam

The Second Generation in Clamp-On Gas Ultrasonic Flow Measurement

 

Historically, clamp-on flow metering was limited to liquids because existing methods could not work on metal pipes containing gases. Several years ago GE developed a new technology that extends all the benefits of

clamp-on flow metering to gas measurement. This breakthrough clamp-on gas flowmeter technology has continued to improve, resulting in the second generation of the DigitalFlow GC868 flowmeter. This remarkable ultrasonic flowmeter works with gases at high or low pressure in pipes made of metal and most other materials. The DigitalFlow GC868 flowmeter can be used to measure the flow of any gas. It is especially useful for

metering erosive, corrosive, toxic, high-purity or sterile gases, or in any application where penetrating the pipe wall is undesirable. Since no tapping or cutting of the pipe is required, permanent installation costs are significantly reduced. The meter has no wetted or moving parts, rarely requires maintenance, causes no pressure drop and has very wide rangeability. The new meter was tested extensively on metal tubes with diameters as small as 0.75 in (20 mm) and pipes as large as 24 in (600 mm). Suitable applications for this meter include flow measurements of air, hydrogen, natural gas, steam and many other gases. Using patented Correlation Transit-Time™ detection techniques, demonstrated accuracy is superb at better than ±2 percent of reading with ±0.5 percent repeatability.

A DigitalFlow GC868 system comprises the DigitalFlow GC868 electronics, a pair of advanced clamp-on gas ultrasonic transducers, a preamplifier, and a clamping fixture for mounting the transducers on the pipe.

 

Advanced Clamp-On Ultrasonic Transducers

 

One of the biggest challenges in developing clamp-on ultrasonic transducers for gas applications is the difficulty in transmitting a coded ultrasonic signal through a metal pipe wall, through the gas, and then

back through the pipe wall to the second transducer that

is waiting to receive the signal. In gas systems, only 4.9 x10–7 percent of the transmitted sound energy is actually received by traditional ultrasonic transducers. This simply isn’t enough to produce reliable measurements. The new line of clamp-on gas transducers produces signals that are five to ten times more powerful than those of traditional ultrasonic transducers. The new transducers produce clean, coded signals with very minimal background noise. The result is that the DigitalFlow GC868 flowmeter system performs well even with low-density gas applications.

 

No Pressure Drop, Low Maintenance

 

Because the transducers clamp onto the outside of the pipe, they do not obstruct the flow inside the pipe. This prevents the pressure drops typically caused by other types of flowmeters. The DigitalFlow GC868 has no

components that will foul or collect debris, and there are no moving parts to wear out. As a result, it requires no lubrication and little or no routine maintenance.

 

Wide Range of Clamping Fixtures Available

 

Transducer alignment is crucial in obtaining accurate measurements in clamp-on gas installations. GE offers a wide range of clamping fixtures to help ensure proper alignment of transducers with minimal effort

 

Convenient Installation

 

Straightforward installation is another advantage of the DigitalFlow GC868 flowmeter. The system consists of one pair of transducers per channel, a clamping fixture, a preamplifier, and an electronics console. The transducers are clamped onto the outside of the existing pipe. The electronics console can be located up to 500 ft (150 m) from the transducers. Set-up and output options allow the DigitalFlow GC868 flowmeter to be customized for any process. For maximum accuracy, use a two-channel meter to average flow measurement along two different paths at the same location or to measure at two different places in the same pipe. A two-channel meter can also measure the flow in two separate pipes.

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