The KROHNE DK37 M8 is a high-performance variable area (VA) flowmeter specifically engineered for advanced low-flow applications. Combining a sturdy all-metal design with state-of-the-art electronic signal output, this metal tube purgemeter is the preferred choice for industrial gas analysis, dosing systems, and chemical injection skids. Whether you require a purely mechanical local indicator or a digital 4…20 mA/HART® output for remote monitoring, the DK37 M8 ensures precision in extreme process conditions—handling pressures up to 220 barg (3190 psig) and temperatures up to +200°C.
In critical process analysis, stability is paramount. The DK37 M8 excels as a sample flow monitoring device for gas analyzers. Its integrated needle valve allows for high-precision flow setting, ensuring that sensitive instruments receive a consistent medium supply. For applications requiring constant flow despite fluctuating inlet or outlet pressures, the DK37 can be factory-equipped with differential pressure regulators, maintaining accuracy where standard meters fail. To achieve comprehensive system-level pressure diagnostics, many engineers pair the DK series with a [Rosemount 3051S Pressure Transmitter] at the conditioning skid inlet.
Safety is a core pillar of the DK37 M8 design. It is fully SIL 2 certified (acc. to IEC 61508) and suitable for use in Safety Instrumented Systems (SIS). For applications requiring a more cost-effective, purely mechanical monitoring solution for even lower flow rates, the [KROHNE DK32/34] series provides a rugged alternative. With ATEX, IECEx, and QPS approvals, the DK37 M8 operates reliably in the world's most demanding explosive atmospheres.
| Feature | Specification Detail |
| Measurement Principle | Variable area float (Metal tube) |
| Application Type | Advanced low-flow monitoring (Liquids and Gases) |
| Accuracy (Standard) | ±2.5% of measured value (acc. to VDI/VDE 3513-2) |
| Accuracy (Optional) | ±2.0% of full-scale value |
| Repeatability | < 0.25% |
| Turndown Ratio | 10:1 |
| Flow Ranges (Water) | 1.6 l/h to 250 l/h (0.4 to 67 GPH) |
| Flow Ranges (Air) | 16 l/h to 8,000 l/h (0.6 to 300 SCFH) |
| Feature | Specification Detail |
| Maximum Process Pressure | 220 barg / 3190 psig |
| Process Temperature | -40°C to +200°C (-40°F to +392°F) |
| Ambient Temperature | -40°C to +70°C (-40°F to +158°F) |
| Inlet/Outlet Requirements | 0D Upstream / 0D Downstream (No straight runs required) |
| Valve Configuration | Integrated needle valve for high-precision flow adjustment |
| Flow Regulation | Optional differential pressure regulators (Inlet or Outlet) |
| Component | Available Materials |
| Measuring Tube | 316L Stainless Steel, Alloy C4, Alloy 400, Titanium (Grade 2), Alloy C276, Alloy 625 |
| Float & Internals | Same as tube material; Optional Ceramic or Ruby for small floats |
| Surface Passivation | SilcoNert®2000 (For trace-level analysis/moisture sensitivity) |
| Indicator Housing | PPS (standard), 316L Stainless Steel (optional for offshore/corrosive air) |
| Gasket Options | PTFE, FFKM, FPM (Process dependent) |
| Connection Type | Specification Detail |
| Thread (Standard) | G¼, ¼ NPT, ½ NPT (Female) |
| Flange Adapters | EN (DN15–25), ASME (½"–1") |
| Tube Fittings | Swagelok, Ermeto, Gyrolok, Serto |
| Other Options | Hose connections, weld ends |
| Output / Protocol | Functionality |
| Local Indicator | Mechanical pointer (M8M) or Electronic Bargraph (M8E) |
| Analogue Output | 4…20 mA (2-wire technology) |
| Digital Protocol | HART® 7 (Optional) |
| Binary Outputs | 1 or 2 limit switches (NAMUR, Reed, or Transistor) |
| Diagnostics | NAMUR NE 107 compliant status indication |
| Category | Compliance / Certification |
| Functional Safety | SIL 2 certified (IEC 61508); SIL 3 in redundant 1oo2 setup |
| Hazardous Area (Ex) | ATEX, IECEx, cQPSus, NEPSI, EAC Ex, INMETRO, UKEX |
| Ingress Protection | IP66/67 (NEMA 4X / 6) |
| Quality/Design | CRN (Canada), NACE MR0175 / MR0103 |
| Nuclear | Qualification available on request (ASME III, RCC-M/E) |
Material Choice: For aggressive acids (chloridic/sulphuric), specify Alloy C276. For high-purity gas analysis, choose SilcoNert®2000 passivation to prevent adsorption of trace components.
Pressure Regulation: If your process pressure varies, always specify the version with an integrated flow regulator (Inlet or Outlet pressure regulation) to avoid measurement drift.
Electronic vs. Mechanical: Use the DK37 M8M for local visual checks without power; use the DK37 M8E (HART) for integration into DCS/SCADA systems.
Orientation: The DK37 M8 must be installed vertically with upward flow. Horizontal or downward flow is not possible with this design.
Connection Types: While G¼ and ¼ NPT are standard, for pharmaceutical or high-pressure gas lines, consider Swagelok or Ermeto tube fittings to minimize leak paths.
Straight Runs: One advantage of VA meters is that they require zero straight pipe runs (0D/0D), allowing for extremely compact analyzer cabinet designs.
The DK37 M8 is virtually maintenance-free due to its lack of moving parts other than the float. However:
Float Cleaning: In applications with additives or "sticky" gases, periodically inspect the float for deposits.
Verification: Use the KROHNE OPTICHECK Flow Mobile App wirelessly via Bluetooth® to verify the electronic indicator’s health without opening the housing.
Safety Audits: For SIS applications, ensure regular proof-testing of the limit switches to maintain SIL compliance.
Q: Can the DK37 M8 maintain a constant flow if the process pressure changes?
A: Yes. The KROHNE DK37 M8 can be equipped with integrated differential pressure regulators. These mechanical regulators automatically adjust to fluctuations in inlet or outlet pressures, ensuring the set flow rate remains stable—a critical feature for sample flow monitoring in gas analyzers.
Q: Why is the SilcoNert®2000 coating used on the DK37 M8?
A: SilcoNert®2000 is a specialized surface passivation. In trace-level analysis (such as detecting moisture or sulfur components), stainless steel can absorb these particles, leading to inaccurate readings. This coating prevents adsorption, ensuring the sample reaching the analyzer is chemically identical to the process fluid.
Q: Is the DK37 M8 suitable for high-pressure hydrogen applications?
A: Absolutely. With a maximum pressure rating of 220 barg (3190 psig) and a sturdy all-metal design (including 316L, Alloy C276, or Titanium), it is an ideal choice for high-pressure chemical injection and hydrogen processing skids.
Q: What installation direction is required for the DK37 M8?
A: Like most variable area flowmeters, the DK37 M8 must be installed in a vertical position with upward flow. However, it offers extreme flexibility with vertical or horizontal process connections (NPT or G thread) to fit tight analyzer cabinets.
