The KOBOLD BGK is an all-metal, low-volume variable area flow meter designed for flow measurement of suitable liquids or gases in pipes. Its measuring cone, float, and armature are stainless steel, and it indicates the current flow rate in volume or mass per unit of time on an analog pointer indicator.
How the BGK Rotameter Measures Flow
Fluid enters at the bottom of the BGK and flows upward through a conical stainless steel measuring tube, lifting a vertically movable float. The float rises until the annular gap between the measuring cone and the float corresponds to the flow rate, at which point the forces acting on the float are in equilibrium.
A permanent magnet inside the float transfers the float height through a magnetic tracking system to the pointer of the analog indicator.
BGK Measuring Ranges and Accuracy
The BGK offers standard measuring ranges from 0.026 to 0.26 GPH (0.1 to 1 l/h) up to 5.3 to 52.8 GPH (20 to 200 l/h) of water, and from 3 to 30 Nl/h up to 600 to 6,000 Nl/h of air. Accuracy for liquids and gases is ±3% qG 50 according to VDE/VDI 3513.
- Repeatability: ±1.0% of the upper range value
- Special gas-only ranges: 6 to 60, 7 to 70, and 11 to 110 Nl/h of air
- Air ranges refer to 14.7 psia (1.013 bar abs) and 68°F (20°C)
- Pressure drop with water: from 0.09 psi (6 mbar) in range A to 0.41 psi (28 mbar) in range K
Materials, Pressure, and Temperature Ratings
The BGK measuring cone, float, and armature are made of stainless steel 1.4404 / 1.4571 (other materials on request); the operating manual identifies 1.4404 as 316L. The polyamide indicator housing has an Ultramid cover and IP65 protection. Maximum pressure depends on the flange rating, up to 580 psi (PN 40, 40 bar).
- Nominal pressure: PN 40 / 300 lbs
- Process temperature without limit contacts or electronics: -40°F to 266°F (-40°C to 130°C)
- Process temperature with 4-20 mA analog output (BGK-..E): -40°F to 212°F (-40°C to 100°C)
- Process temperature with NJ1.5-6.5N limit contacts: -13°F to 212°F (-25°C to 100°C)
- Weight: 5.3 lb (2.4 kg)
Process Connections and Dimensions
The BGK installs between flanges: DIN EN 1092-1 DN 10, DN 15, or DN 25 (PN 40), or ASME B16.5 1/2", 3/4", or 1" (Class 150 or 300 raised face, with a 1" ring type joint option). Special connections are available. Overall flange-to-flange length is 9.84 in (250 mm).
Limit Switches and 4-20 mA Analog Output
The BGK is available as a purely mechanical meter or with electrical equipment for process monitoring and control: one or two inductive NAMUR limit contacts, one inductive contact for safety functions (NJ2-11-SN), or the BGK-..E version with a 4-20 mA analog transmitter. All connect via an M12 plug.
- NJ1.5-6.5N limit contacts: NAMUR, 8.2 V (Ri approx. 1 kΩ)
- Analog output: 4-20 mA, 2-wire, passive, 14 to 30 V, load max. 500 Ω, without HART, intrinsically safe (Ex ib)
Hazardous Area Approvals and Certificates
The BGK carries ATEX explosion protection certification, with the mechanical version registered under BVS 03 ATEX H/B 113. The BGK-..E analog output version is certified under BVS 12 ATEX E 093 X and IECEx BVS 12.0061X, and the datasheet lists SIL conformity according to IEC 61508-2 for the device.
- BGK-..E marking: II 2 G Ex ib IIC T4 Gb or II 2D Ex ib IIIC T135 °C Db
- Material and inspection certificates on request: 2.1, 2.2, 3.1, and 3.2 per DIN EN 10204:2004
BGK Installation Requirements
The BGK must be installed vertically with flow from bottom to top, using a line size that matches the device connection. Align pipe flanges parallel for stress-free mounting, do not use steel mounting parts on the device, and do not install a valve directly in front of it.
- Minimum lateral distance: 11.8 in (300 mm) between adjacent meters, 7.9 in (200 mm) from interfering steel parts
- Inlet section: not required for a linear flow profile; 5.9 in (150 mm) recommended for a non-linear profile
- Avoid solenoid valves, which can make the float shoot upward at start-up; raise gas inlet pressure slowly
Common Questions about BGK - All-Metal, Low-Volume Variable Area Flow Meter
The BGK uses the float principle. Product passes vertically through the meter from bottom to top and lifts the float until buoyancy force and float weight balance. Float height is a measure of the flow quantity, and a built-in permanent magnet converts that position into rotary motion on the indicator pointer.
Standard BGK ranges run from range A, 0.026 to 0.26 GPH (0.1 to 1.0 l/h) water or 3 to 30 Nl/h air, through range K, 5.3 to 52.8 GPH (20 to 200 l/h) water or 600 to 6,000 Nl/h air. Three extra gas-only ranges cover 6 to 60, 7 to 70, and 11 to 110 Nl/h.
The max pressure is 580 psi (PN 40, 40 bar), with the flange rating governing. Process temperature reaches 266°F (130°C) on the purely mechanical meter, while versions fitted with limit contacts or the 4-20 mA transmitter have a 212°F (100°C) maximum process temperature.
Flange choices include DN 10, DN 15, and DN 25 at PN 40 to DIN EN 1092-1, and 1/2", 3/4", and 1" ASME B16.5 flanges rated Class 150 or 300 with raised faces. The 1" size can also be ordered with ring type joint facing, and KOBOLD can supply special connections.
Electrical equipment is optional. The BGK can be fitted with one or two NAMUR contacts, a single NJ2-11-SN contact for safety functions, or a passive, loop-powered 4-20 mA transmitter (BGK-..E) operating on 14 to 30 V with a 500 Ω maximum load. Each option uses an M12 plug.
ATEX registration BVS 03 ATEX H/B 113 covers the purely mechanical BGK. The 4-20 mA BGK-..E carries BVS 12 ATEX E 093 X and IECEx BVS 12.0061X with Ex ib protection, and the inductive contacts carry Ex ia approvals PTB 00 ATEX 2048 X (NJ1.5-6.5N) or PTB 00 ATEX 2049 X (NJ2-11-SN).
Mount the meter upright so flow travels upward, using piping the same size as the meter connection. Keep neighboring meters 11.8 in (300 mm) apart and steel parts 7.9 in (200 mm) away to avoid magnetic interference.
Compare actual process data (density, viscosity, temperature, and pressure) with the values printed on the scale. If they differ, the scale values can be converted using VDE/VDI 3513. A float stuck by dirt calls for disassembly and cleaning, plus a magnetic filter where magnetic contaminants are present.
No maintenance is required when the BGK is used as intended. If the float or measuring ring needs cleaning, first confirm the pipeline is empty, depressurized, and cooled down before removing the meter, then clean coated fittings carefully with a brush and a suitable cleaning agent.
Product Specifications
Measuring Range
0.1...1 L/h to 20...200 L/h
Measuring Range
3...30 Nl/h to 600...6000 Nl/h
Fittings
DIN Flange DN 10...25 or ANSI 1/2"...1"
Wetted Material
316 St. Steel
Max. Pressure
Per Flange Rating
Max. Temperature
-40...130 °C (-25...100 °C w/Contact; -40...100 °C w/Analog Output)
Media Categories
Liquid or Gas
Product Features
For Measurement of Low Flow Rates
Optional Switches, Analog Transmitter
Certificates/Approvals: ATEX, SIL, IECEx
Documents
Software Downloads
There are no downloads to display at this time. If you think this is incorrect, please contact us and let us know the issue you are having.
Videos
There are no videos to display at this time. If you think this is incorrect, please contact us and let us know the issue you are having.