The KROHNE DK46/47/48/800 series represents the industry standard for glass tube variable area flowmeters. Engineered for high-precision monitoring of extremely small flow rates (from ≥0.04 l/h), these purgemeters provide a clear, direct-reading analogue scale for liquids and gases. Whether integrated into gas chromatographs, pilot installations, or purge panels, the DK series delivers a reliable, power-free measurement solution. With a sturdy design supporting temperatures up to +100°C and optional SIL 2 safety compliance, it is the essential tool for laboratories and process analyzer sample conditioning systems.
Visual confirmation is critical in laboratory and analytical environments. The DK46/47/48/800 features a high-quality borosilicate glass measuring tube, allowing operators to see the medium and the float position instantly. This transparency is vital for detecting impurities or bubbles in sample lines. To ensure a constant flow rate despite fluctuating inlet or outlet pressures, the DK series can be equipped with an integrated differential pressure regulator, a must-have for maintaining the stability of sensitive gas analyzers and carrier gas systems.
While the borosilicate glass tube offers unmatched visibility for laboratory dosing, applications requiring similar precision with a digital bargraph indicator should explore the [KROHNE DK37 M8], which combines low-flow accuracy with HART® 7 communication.
Versatility is the core of the DK glass series. These meters are available in multiple installation lengths (90 to 325 mm) to fit any cabinet footprint.
Panel Mounting: Optimized for purge panels and blinds.
Desktop Units: Convertible for laboratory benchtop use via specialized lab supports.
Safety Integration: Despite being a glass-tube meter, specific configurations are SIL 2 certified, making them suitable for nitrogen inertization and other Safety Instrumented Systems (SIS).
| Feature | Specification Detail |
| Measurement Principle | Variable area float (Glass tube) |
| Accuracy (Standard) | ±1.0% / ±2.5% / ±4.0% (acc. to VDI/VDE 3513-2) |
| Accuracy (Full Scale) | ±1.0% / ±2.0% / ±3.0% of full-scale value |
| Repeatability | < 0.25% |
| Turndown Ratio | 10:1 |
| Flow Ranges (Water) | From ≥0.04 l/h (≥0.01 GPH) to 160 l/h |
| Flow Ranges (Air) | From ≥5 Nl/h (≥0.22 SCFH) to 5,000 Nl/h |
| Model | Tube Length | Standard Height |
| DK46 | 65 mm / 2.56" | 90 mm / 3.55" |
| DK800 | 150 mm / 5.91" | 175 mm / 6.89" |
| DK47 | 175 mm / 6.89" | 200 mm / 7.87" |
| DK48 | 300 mm / 11.8" | 325 mm / 12.8" |
| Feature | Specification Detail |
| Maximum Pressure | 10 barg / 145 psig (Standard) |
| Process Temperature | -5°C to +100°C (+23°F to +212°F) |
| Ambient Temperature | -20°C to +100°C (-4°F to +212°F) |
| Straight Run Req. | 0D Upstream / 0D Downstream |
| Inlet/Outlet Direction | Vertical Bottom-to-Top (Standard) |
| Pressure Compensation | Available with mechanical differential pressure regulators |
| Component | Available Materials |
| Measuring Tube | Borosilicate glass (High-precision calibrated) |
| Fittings / Connections | 316L Stainless Steel, Nickel-plated Brass, PVDF |
| Floats | Stainless Steel, Titanium, Glass, Ceramic, Ruby, Agate |
| Valve Internals | Stainless steel or matching fitting material |
| Gasket Selection | EPDM (Standard), PTFE, FFKM, FPM |
| Housing / Blind | PPS (Poly-phenylene sulphide) |
| Feature | Specification Detail |
| Thread (Standard) | G¼ (Internal), ¼ NPT (Internal) |
| Tube Fittings | Swagelok, Ermeto, Serto, Gyrolok |
| Hygienic/Hose | Various hose barbs available |
| Mounting Options | Panel mount (for purge panels), Lab support (desktop unit) |
| Output Type | Functionality |
| Local Indication | Direct reading on the glass tube scale |
| Binary Signals | Max. 2 Limit Switches (NAMUR or Reed) |
| Digital Output | 3-wire digital output (Optional) |
| Communication | None (Purely mechanical principle) |
| Category | Certification / Standard |
| Functional Safety | SIL 2 certified (IEC 61508) |
| Hazardous Area (Ex) | ATEX, NEPSI, PESO, UKEX |
| Nuclear Qualification | Available on request (e.g., ASME III, RCC-M/E) |
| Ingress Protection | IP65 (Standard) |
For laboratory and pilot plant applications where exact flow control is the difference between success and failure, the DK48 (300mm tube) is recommended. Its long scale provides the highest resolution for manual adjustment, allowing technicians to dial in flow rates as low as 0.04 l/h with extreme repeatability.
When dealing with aggressive chemicals or corrosive sample gases in environmental monitoring, the PVDF fitting option combined with FFKM gaskets ensures that the flowmeter body remains unaffected by chemical attack. This makes the DK series a more durable choice than plastic-body meters for industrial-grade analysis.
In nitrogen purge applications, the header pressure often drops when other users activate. By specifying an integrated differential pressure regulator (inlet or outlet), the DK series maintains a steady flow regardless of these fluctuations. This is critical for preventing "starvation" of gas chromatographs or sample conditioning systems.
For advanced sample conditioning systems where inlet pressure fluctuates significantly, pairing this meter with a [Rosemount 3051S Pressure Transmitter] provides the necessary real-time data to ensure your analyzer is always correctly primed.
Q: What are the primary differences between the DK46, DK47, DK48, and DK800 models?
A: The main difference lies in the tube length and scale resolution.
DK46: The most compact model (90 mm / 3.55"), ideal for space-restricted panels.
DK800 & DK47: Intermediate lengths (175–200 mm) offering a balance between size and readability.
DK48: The longest model (325 mm / 12.8"), providing the highest resolution for extremely precise manual flow adjustment and monitoring.
Q: Can the DK series maintain a constant flow if my process pressure fluctuates?
A: Yes. For applications like gas chromatography or nitrogen purging where inlet or outlet pressures vary, we can equip the meter with an integrated differential pressure regulator. This mechanical regulator compensates for pressure changes to maintain a steady, accurate flow rate, preventing "starvation" or surging in your analytical system.
Q: Is a glass tube flowmeter safe for industrial or hazardous environments?
A: Absolutely. The DK series uses high-quality, calibrated borosilicate glass and is housed in a rugged frame with a protective cover. It is SIL 2 certified (acc. to IEC 61508) for use in Safety Instrumented Systems (SIS). However, for applications involving extremely high pressures (>10 barg) or lethal chemicals where glass breakage is an unacceptable risk, we recommend the all-metal [KROHNE DK32/34]as a safer alternative.
Q: Does the DK46/47/48/800 require straight inlet or outlet pipe runs?
A: No. One of the greatest advantages of this variable area principle is the 0D/0D installation. Because the measurement does not depend on the fluid's velocity profile, you can install the meter directly after elbows, valves, or T-junctions. This makes it perfect for compact analyzer cabinets and purge panels where space is limited.
