DigitalFlow™
GC868

Panametrics clamp-on
gas ultrasonic flowmeter
Applications

Features

The DigitalFlow GC868 clamp-on gas flowmeter is acomplete ultrasonic flow metering system for measurementof most gases, including:• Clamp-on unobstructed installation• Natural gas• Compressed air• Fuel gases• Erosive gases• Corrosive gases• Toxic gases• High-purity gases• Air separation gases• No wetted parts• Two-channel/two-path version available• No moving parts• No pressure drop
• Sound speed output• Simple installation• Standard volumetric flow calculation• Supercompressibility compensation• Suitable for a wide range of temperatures and pressures

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 Panametrics 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 ultrasonicflowmeter 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 withdiameters 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, and many othergases. 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 ultrasonictransducers, a preamplifier, and a clamping fixture formounting 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 intransmitting a coded ultrasonic signal through a metal pipewall, through the gas, and then back through the pipe wall tothe second transducer that is waiting to receive the signal.
In gas systems, only 4.9 x 10–7 percent of the transmitted
sound energy is actually received by traditional ultrasonictransducers. This simply isn’t enough to produce reliablemeasurements.
The new line of clamp-on gas transducers produces
signals that are five to ten times more powerful than thoseof traditional ultrasonic transducers. The new transducers
produce clean, coded signals with very minimal backgroundnoise. The result is that the DigitalFlow GC868 flowmetersystem performs well even with low-density gas applications.

Panametrics technologically advanced
clamp-on gas ultrasonic transducers

No pressure drop, low maintenanceBecause the transducers clamp onto the outside of the pipe,
they do not obstruct the flow inside the pipe. This prevents thepressure drops typically caused by other types of flowmeters.
The DigitalFlow GC868 has no components that will foul orcollect 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. Panametrics
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 theDigitalFlow GC868 flowmeter. The system consists of one
pair of transducers per channel, a clamping fixture, apreamplifier, and an electronics console. The transducers areclamped onto the outside of the existing pipe. The electronics
console can be located up to 500 ft (150 m) from thetransducers. Set-up and output options allow the DigitalFlow
GC868 flowmeter to be customized for any process.
For maximum accuracy, use a two-channel meter toaverage flow measurement along two different paths at thesame location or to measure at two different places in thesame pipe. A two-channel meter can also measure the flowin two separate pipes.

Optional temperaturetransmitter
Downstream
transducer

Optional pressuretransmitter

Flow

Upstreamtransducer

The DigitalFlow GC868 flowmeter uses thetransit-time flow measurement technique
The transit-time technique uses a pair of transducers, witheach transducer sending and receiving coded ultrasonicsignals through the fluid. When the fluid is flowing, signaltransit time in the downstream direction is shorter than in
the upstream direction; the difference between these transit
times is proportional to the flow velocity. The DigitalFlow
GC868 measures this time difference and uses programmed
pipe parameters to determine flow rate and direction.

Typical meter set-up for standard volumetricTransducer

Gas flow

Transducer

Ultrasonicsignal path

Transit-time flow measurement technique

GC868 installation requirements for air, nitrogen, oxygen or argon
Pipe size
ANSI (DIN)

Pipe wallin (mm)Tranducer
MHz

Minimum pressure
psig (bar)Maximum velocity, ft/s (m/s) - traverse
SingleDual

TripleFourFive

3/4 (20)≤ 0.07 (1.8)

160 (5.1)——

90 (27.4)——

1 (25)≤ 0.14 (3.6)

1

60 (5.1)——

90 (27.4)—

90 (27.4)

1 1/2 (40)

≤ 0.15 (3.8)

1

60 (5.1)——

90 (27.4)—

57 (17.4)

2 (50)≤ 0.16 (4.1)

1

60 (5.1)

90 (27.4)—

75 (22.9)—

45 (13.7)

3 (75)≤ 0.2

1

60 (5.1)

120 (36.6)—

69 (21.0)

46 (14.0)—

3 (75)≤ 0.22 (5.6)

0.5

60 (5.1)

120 (36.6)—

69 (21.0)

46 (14.0)—

4 (100)≤ 0.2

160 (5.1)

120 (36.6)—

53 (16.2)

35 (10.7)—

4 (100)≤ 0.24 (6.1)

0.5

60 (5.1)

120 (36.6)—

53 (16.2)

35 (10.7)—

4 (100)≤ 0.34 (8.6)

0.5

180 (13.4)

120 (36.6)—

53 (16.2)

35 (10.7)—

4 (100)≤ 0.68 (17.3)

0.5

300 (21.7)

120 (36.6)—

53 (16.2)

35 (10.7)—

6 (150)≤ 0.2

160 (5.1)

90 (27.4)

72 (22.0)

54 (16.5)——

6 (150)≤ 0.28 (7.2)

0.5

60 (5.1)

90 (27.4)

72 (22.0)

54 (16.5)——

6 (150)≤ 0.28 (7.2)

0.2

60 (5.1)

90 (27.4)

72 (22.0)

54 (16.5)——

6 (150)≤ 0.44 (11.2)

0.5

180 (13.4)

90 (27.4)

72 (22.0)

54 (16.5)——

6 (150)≤ 0.44 (11.2)

0.2

180 (13.4)

90 (27.4)

72 (22.0)

54 (16.5)——

6 (150)≤ 0.87 (22.1)

0.5

300 (21.7)

90 (27.4)

72 (22.0)

54 (16.5)——

6 (150)≤ 0.87 (22.1)

0.2

300 (21.7)

90 (27.4)

72 (22.0)

54 (16.5)——

8 (200)≤ 0.33 (8.4)

0.5

60 (5.1)

80 (24.4)

64 (19.5)

48 (14.6)——

8 (200)≤ 0.33 (8.4)

0.2

200 (13.6)

120 (36.6)

96 (29.3)

72 (21.9)———8 (200)≤ 0.50 (12.7)

0.5

180 (13.4)

80 (24.4)

64 (19.5)

48 (14.6)—

8 (200)≤ 0.50 (12.7)

0.2

600 (40.8)

120 (36.6)

96 (29.3)

72 (21.9)——8 (200)≤ 0.88 (22.4)

0.5

300 (21.7)

80 (24.4)

64 (19.5)

48 (14.6)——

8 (200)≤ 0.88 (22.4)

0.21000 (68)120 (36.6)

96 (29.3)

72 (21.9)——

10 (250)≤ 0.37 (9.4)

0.5

60 (5.1)

70 (21.3)

56 (17.1)

42 (12.8)——

10 (250)≤ 0.37 (9.4)

0.2

200 (13.6)

105 (32)

84 (25.6)

63 (19.28)——

10 (250)≤ 0.50 (12.7)

0.5

180 (13.4)

70 (21.3)

56 (17.1)

42 (12.8)——

10 (250)≤ 0.50 (12.7)

0.2

600 (40.8)

105 (32)

84 (25.6)

63 (19.28)——

10 (250)≤ 1.00 (25.4)

0.5

300 (21.7)

70 (21.3)

56 (17.1)

42 (12.8)——

10 (250)≤ 1.00 (25.4)

0.51000 (68)105 (32)

84 (25.6)

63 (19.28)——

12 (300)≤ 0.38 (9.7)

0.5

60 (5.1)

55 (16.8)

44 (13.4)

33 (10.1)——

12 (300)≤ 0.38 (9.7)

0.2

200 (13.6)

82 (25)66 (20.1)

49 (14.9)——

12 (300)≤ 1.00 (25.4)

0.2

180 (13.4)

55 (16.8)

44 (13.4)

33 (10.1)——

12 (300)≤ 0.38 (9.7)

0.2

600 (40.8)

82 (25)66 (20.1)

49 (14.9)——

12 (300)≤ 0.50 (12.7)

0.2

300 (21.7)

55 (16.8)

44 (13.4)

33 (10.1)——

12 (300)≤ 1.00 (25.4)

0.21000 (68)82 (25)66 (20.1)

49 (14.9)——

14 (350)≤ 0.38 (9.7)

0.2

90 (7.2)

87 (26.5)

70 (21.3)

52 (15.9)——

14 (350)≤ 0.50 (12.7)

0.2

270 (19.6)

87 (26.5)

70 (21.3)

52 (15.9)——

16 (400)≤ 0.38 (9.7)

0.2

90 (7.2)

76 (23.2)

61 (18.9)45 (13.7)——

16 (400)≤ 0.50 (12.7)

0.2

270 (19.6)

76 (23.2)

61 (18.9)45 (13.7)——

18 (450)≤ 0.38 (9.7)

0.2

90 (7.2)

67 (20.4)

54 (16.5)

40 (12.2)——

18 (450)≤ 0.50 (12.7)

0.2

270 (19.6)

67 (20.4)

54 (16.5)

40 (12.2)——

20 (500)≤ 0.38 (9.7)

0.2

90 (7.2)

60 (18.3)

48 (14.6)

36 (11.0)——

20 (500)≤ 0.50 (12.7)

0.2

270 (19.6)

60 (18.3)

48 (14.6)

36 (11.0)——

24 (600)≤ 0.38 (9.7)

0.2

90 (7.2)

49 (14.9)

39 (11.9)

29 (8.8)——

24 (600)≤ 0.50 (12.7)

0.2

270 (19.6)

49 (14.9)

39 (11.9)

29 (8.8)——

How to use this table.
1. Find pipe size of your application.
2. Find pipe wall thickness of your application.
A. Determine if your application meets the minimum pressure requirements given pipe size and pipe wall thickness as determined by pipe wall
thickness.
B. Determine maximum flow velocity capability.
3. Consult factory for natural gas with sulfur or high carbon dioxide content.
4. Consult factory for applications that are not listed above.

GC868 installation requirements for natural gas
Maximum velocity, ft/s (m/s)

Pipe size
ANSI (DIN)

Pipe wallin (mm)Tranducer
MHz

Minimum pressure
psig (bar)Single traverse

Dual traverse

Triple traverse

2 (50)≤ 0.16 (4.1)

0.5

200 (14.8)

110 (33.5)

88 (26.8)

66 (20.5)

3 (75)≤ 0.22 (5.6)

0.5

200 (14.8)

120 (36.6)

96 (29.3)

72 (22.0)

4 (100)≤ 0.24 (6.1)

0.5

150 (11.4)

120 (36.6)

96 (29.3)

72 (22.0)

4 (100)≤ 0.34 (8.6)

0.5

400 (28.6)

120 (36.6)

96 (29.3)

72 (22.0)

4 (100)≤ 0.68 (17.3)

0.5

800 (56.2)

120 (36.6)

96 (29.3)

72 (22.0)

6 (150)≤ 0.28 (7.2)

0.5

150 (11.4)

120 (36.6)

96 (29.3)

72 (22.0)

6 (150)≤ 0.28 (7.2)

0.2

250 (17)180 (54.9)

144 (43.9)

108 (32.9)

6 (150)≤ 0.28 (7.2)

0.5

400 (28.6)

120 (36.6)

96 (29.3)

72 (22.0)

6 (150)≤ 0.44 (11.2)

0.2

500 (34)

180 (54.9)

144 (43.9)

108 (32.9)

6 (150)≤ 0.87 (22.1)

0.5

800 (56.2)

120 (36.6)

96 (29.3)

72 (22.0)

6 (150)≤ 0.87 (22.1)

0.21000 (68)180 (54.9)

144 (43.9)

108 (32.9)

8 (200)≤ 0.33 (8.4)

0.5

60 (5.1)

100 (30.5)

80 (24.4)

60 (18.3)

8 (200)≤ 0.33 (8.4)

0.2

200 (13.6)

150 (45.7)

120 (36.6)

90 (27.4)

8 (200)≤ 0.50 (12.7)

0.5

180 (13.4)

100 (30.5)

80 (24.4)

60 (18.3)

8 (200)≤ 0.50 (12.7)

0.2

600 (40.8)

150 (45.7)

120 (36.6)

90 (27.4)

8 (200)≤ 0.88 (22.4)

0.5

300 (21.7)

100 (30.5)

80 (24.4)

60 (18.3)

8 (200)≤ 0.88 (22.4)

0.21000 (68)150 (45.7)

120 (36.6)

90 (27.4)

10 (250)≤ 0.37 (9.4)

0.5

60 (5.1)

85 (25.9)

68 (20.7)51 (15.6)

10 (250)≤ 0.37 (9.4)

0.2

200 (13.6)

126 (38.4)

102 (31.1)

75 (22.0)

10 (250)≤ 0.50 (12.7)

0.5

180 (13.4)

85 (25.9)

68 (20.7)51 (15.6)

10 (250)≤ 0.50 (12.7)

0.2

600 (40.8)

126 (38.4)

102 (31.1)

75 (22.0)

10 (250)≤ 1.00 (25.4)

0.5

300 (21.7)

85 (25.9)

68 (20.7)51 (15.6)

10 (250)≤ 1.00 (25.4)

0.51000 (68)126 (38.4)

102 (31.1)

75 (22.0)

12 (300)≤ 0.38 (9.7)

0.5

60 (5.1)

70 (21.3)

56 (17.1)

42 (12.8)

12 (300)≤ 0.38 (9.7)

0.2

200 (13.6)

105 (32)

84 (25.6)

63 (19.28)

12 (300)≤ 1.00 (25.4)

0.2

180 (13.4)

70 (21.3)

56 (17.1)

42 (12.8)

12 (300)≤ 0.38 (9.7)

0.2

600 (40.8)

105 (32)

84 (25.6)

63 (19.28)

12 (300)≤ 0.50 (12.7)

0.2

300 (21.7)

70 (21.3)

56 (17.1)

42 (12.8)

12 (300)≤ 1.00 (25.4)

0.21000 (68)105 (32)

84 (25.6)

63 (19.28)

14 (350)≤ 0.38 (9.7)

0.2

90 (7.2)

103 (31.4)

77 (23.5)

62 (18.9)

14 (350)≤ 0.50 (12.7)

0.2

270 (19.6)

103 (31.4)

77 (23.5)

62 (18.9)

16 (400)≤ 0.38 (9.7)

0.2

90 (7.2)

90 (27.4)

67 (20.4)

54 (16.5)

16 (400)≤ 0.50 (12.7)

0.2

270 (19.6)

90 (27.4)

67 (20.4)

54 (16.5)

18 (450)≤ 0.38 (9.7)

0.2

90 (7.2)

78 (23.8)

59 (18.0)

47 (14.3)

18 (450)≤ 0.50 (12.7)

0.2

270 (19.6)

78 (23.8)

59 (18.0)

47 (14.3)

20 (500)≤ 0.38 (9.7)

0.2

90 (7.2)

70 (21.3)

52 (15.9)42 (12.8)

20 (500)≤ 0.50 (12.7)

0.2

270 (19.6)

70 (21.3)

52 (15.9)42 (12.8)

24 (600)≤ 0.38 (9.7)

0.2

90 (7.2)

56 (17.1)

42 (12.8)

34 (10.4)

24 (600)≤ 0.50 (12.7)

0.2

270 (19.6)

56 (17.1)

42 (12.8)

34 (10.4)

GC868 specifications
Operation and performanceElectronics

Fluid types
Acoustically conductive gases with minimum density
requirements (see Installation requirements table)

Flow measurement
Correlation transit-time mode

Pipe sizes• Most gases: 0.75 to 24 in NB(20 to 600 mm DN) and larger

Pipe wall thickness
Thicker walled pipes require higher gas density (seeinstallation requirements table)
Pipe materials
Most metals and plastics. No lined pipes.
Flow accuracy (velocity)• For pipes 6 in (150 mm) and smaller:±2% to 5% of reading typical• For pipes larger than 6 in (150 mm):
±1% to 2% of reading typicalAccuracy depends on pipe size and whether measurement is one-path or
two-path. Accuracy to ±0.5% of reading may be achievable with processcalibration.

Repeatability±0.2% to 0.5% of reading
Range (bidirectional)
See installation requirements table
Rangeability (overall)
See installation requirements table
Specifications assume a fully developed flow profile (typically 20
diameters upstream and 10 diameters downstream of straight pipe run)and flow velocity greater than 5 ft/s (1.5 m/s).

Measurement parameters
Standard and actual volumetric flow, and flow velocity

Enclosures• Standard: epoxy-coated aluminumType 4X/IP66 Class I, Division 2, Groups A,B,C&D• Optional: Stainless steel, fiberglass, explosion-proof,
II 2 G EEx d IIC T6)
flameproof
Dimensions
Standard: weight 11 lb (5 kg), size (h x w x d)
14.24 x 11.4 x 5.1 in (362 x 290 x 130 mm)
Channels• Standard: one-channel• Optional: two-channel (for two pipes or
two-path averaging)
Display
Two independent software-configurable 64 x 128 pixel backlit
LCD graphic displays
Keypad39-key, tactile-feedback membrane keypad
Power supplies• Standard: 100 to 130 VAC, 50/60 Hz or 200 to
265 VAC, 50/60 Hz• Optional: 12 to 28 VDC, ±5%Power consumption
20 W maximum
Operating temperature–10° to 55°C (14° to 130°F)
Storage temperature–40° to 70°C (–40° to 158°F)
Standard inputs/outputs
Two 0/4 to 20 mA isolated outputs, 550 Ω maximum load

GC868 specifications

Optional inputs/outputs
There are six additional slots available for any combination of
the following I/O boards:• Analog outputs: select up to three additional output
boards, each with four isolated 0/4 to 20 mA outputs, 1 kΩmaximum load
• Analog inputs: select up to three boards of one of thefollowing types:­ – Analog input board with two isolated 4 to 20 mA inputs
and 24 V loop power­ – RTD input board with two isolated, three-wire, RTD inputs;
span –100° to 350°C (–148° to 662°F); 100 Ω Pt
• Totalizer/frequency outputs: Select up to three totalizer/
frequency output boards, each with four outputs per board,
10 kHz maximum. All boards allow software-selectablefunctioning in two modes:­ – Totalizer mode: pulse per defined unit of parameter(e.g., 1 pulse/ft3)­ – Frequency mode: pulse frequency proportional tomagnitude of parameter (e.g., 10 Hz = 1 ft3/h)• Alarm relays: select up to two boards of one of thefollowing types:­ –G eneral purpose: relay board with three Form C relays;
120 VAC, 28 VDC maximum, 5 A maximum; DC 30 W
maximum, AC 60 VA­ –H
 ermetically sealed: relay board with three hermeticallysealed Form C relays; 120 VAC, 28 VDC maximum, 2 A
maximum; DC 56 W maximum, AC 60 VA

Digital interfaces• Standard: RS232• Optional: RS485 (multiuser)• Optional: Modbus® RS458 or TCP protocol• Optional: Ethernet• Optional: OPC server• Optional: Foundation fieldbus
Site parameter programming
Menu-driven operator interface using keypad and “soft”
function keys
Data logging
Memory capacity (linear and/or circular type) to log morethan 43,000 flow data points
Display functions• Graphic display shows flow in numerical or graphic format• Displays logged data and diagnostics

European compliance
Complies with EMC Directive 89/336/EEC, 73/23/EEC LVD(Installation Category II, Pollution Degree 2)

Clamp-on ultrasonic flow transducers
Temperature ranges• Standard: –40° to 130°C (–40° to 266°F)• Optional (overall range): –40° to 230°C (–40° to 446°F)
Mountings
Anodized aluminum or stainless steel clamping fixture withrigid rails, chain or strap• 0.75 to 1.25 in (20 to 30 mm) pipe: CFG-V1• 1.25 to 4 in (30 to 100 mm) pipe: CFG-V4• 4 to 8 in (100 to 200 mm) pipe: CFG-V8• 8 to 12 in (200 to 300 mm) pipe: CFG-V12• 12 to 24 in (300 to 600 mm) pipe: CFG-PI

Panametrics, a Baker Hughes Business, provides solutions in
the toughest applications and environments for moisture,oxygen, liquid and gas flow measurement. Experts in flaremanagement, Panametrics technology also reduces flareemissions and optimizes performance.
With a reach that extends across the globe, Panametrics’
critical measurement solutions and flare emissions
management are enabling customers to drive efficiency
and achieve carbon reduction targets across criticalindustries including: Oil & Gas; Energy; Healthcare; Water andWastewater; Chemical Processing; Food & Beverage andmany others.

Mounting couplant
CPL-16
Area classifications• Standard: General purpose• Optional: Weatherproof Type 4X/IP65• Optional: Explosion-proof Class I, Division 1, Groups B,C,&D• Optional: Flameproof

II 2 G EEx md IIC T6–T3

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BHCS38687		

(05/2023)

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