The KROHNE H250 M40 is the world’s most versatile variable area flowmeter, combining robust mechanical measurement with cutting-edge digital communication. Designed for both the process industry and OEM equipment, the H250 M40 offers a modular architecture that adapts to your evolving needs—from simple local indication to full HART 7, FF, and Profibus-PA integration. Whether handling cryogenic liquids at -196°C or aggressive chemicals at high pressures up to 1000 barg, this all-metal rotameter ensures process safety and long-term stability without requiring auxiliary power for its basic functions.
The H250 M40 stands out due to its modularity. Unlike standard meters, its functionality can be upgraded on-site without process interruption. You can start with a mechanical indicator and later add:
ESK4A Electronic Module: For 2-wire 4…20 mA/HART 7 output.
Limit Switches: For high/low flow alarms in Safety Instrumented Systems (SIL 2).
LCD Totalizers: For local digital flow accumulation and pulse output.
A major pain point in piping design is the lack of vertical space. While most rotameters require vertical upward flow, the H250 M40 offers specialized spring-loaded versions for horizontal and descending pipe installations (up to DN150 / 6"). In aseptic processing and clean-room environments, the H250 M40 pairs perfectly with the [KROHNE OPTIFLUX 6400], our 3A and EHEDG certified flowmeter designed for precise food and beverage dosing.
| Parameter | Specification Details |
| Measurement Principle | Variable area float (Mechanical-Inductive) |
| Primary Measured Media | Liquids, Gases, and Steam |
| Accuracy (Liquids/Gases) | ±1.6% of Measured Value (acc. to VDI/VDE 3513-2) or ±1.5% of Full Scale |
| Repeatability | < 0.25% |
| Turndown Ratio | 10:1 (Standard); up to 100:1 (Optional with specialized floats) |
| Flow Ranges (Water) | 10 l/h up to 120,000 l/h (5 to 32,000 GPH) |
| Flow Ranges (Air) | 0.7 m³/h up to 2800 m³/h (25 to 100,000 SCFH) |
| Parameter | Limits & Ratings |
| Maximum Pressure | Standard: 40–100 barg; High Pressure Version: 1000 barg (14,500 psig) |
| Process Temperature | -196°C to +400°C (-320°F to +752°F) |
| Ambient Temperature | -40°C to +80°C (-40°F to +176°F) |
| Inlet/Outlet Runs | 0D / 0D (Virtually no straight run requirements) |
| Installation Direction | Vertical (Standard); Horizontal & Descending (with spring-loaded float) |
| Component | Available Materials |
| Measuring Tube | 316L Stainless Steel, Alloy C4, Alloy 400, Titanium (Grade 2), Alloy C276, Alloy 625, 6Mo |
| Float & Internals | Same as tube material; Ceramic or specialized coatings available for abrasion |
| Indicator Housing | Die-cast Aluminum (epoxy coated) or 316L Stainless Steel (for offshore/corrosive environments) |
| Gaskets | None (Metal-to-metal seal or fully welded construction) |
| Protocol / Output | Technical Features |
| Analogue Output | 4…20 mA with HART® 7 (ESK4A module) |
| Digital Fieldbus | FOUNDATION™ Fieldbus, Profibus-PA |
| Binary Outputs | Up to 2 Limit Switches (NAMUR, Transistor, or Reed) |
| Local Display | Mechanical pointer (standard); Optional LCD for totalization and bar graphs |
| Diagnostics | NE 107 compliant; Continuous Float Monitoring (CFM) for blockage detection |
| Category | Compliance / Standard |
| Functional Safety | SIL 2 certified (acc. to IEC 61508) |
| Explosion Protection | ATEX, IECEx, NEPSI, cFMus (Intrinsically Safe & Explosion Proof) |
| Hygienic | FDA, EC 1935/2004 (Available with Clamp or DIN 11851 connections) |
| Marine | RINA (Other class approvals on request) |
| Nuclear | Qualification according to ASME III, RCC-M/E available |
Medium Properties: For aggressive media, select Alloy C276 or Titanium. For highly abrasive slurries or aggressive chemicals that exceed standard metal limits, our [KROHNE OPTIFLUX 5400] with a high-tech ceramic tube provides unrivaled resistance.
Accuracy vs. Pipeline Size: While the H250 M40 is the standard for VA metering, for high-precision water billing or larger pipe sizes, we recommend the [KROHNE WATERFLUX 3400] with its unique 0D/0D installation technology.
System Integration: For complete skid monitoring or injection modules, the H250 M40 can be integrated with the [Rosemount 3051S Pressure Transmitter] to provide real-time pressure diagnostics alongside flow data.
Unlike standard glass or metal rotameters that rely purely on gravity, the H250 M40 offers a spring-loaded float option.
The Problem: In many skids, vertical upward flow is impossible due to space constraints.
The Solution: The spring-loaded H250 allows for horizontal or descending pipe installation. This allows for much more compact piping designs without losing the mechanical reliability of a VA meter.
When measuring gases at low pressures or in systems with high volumes, "float bounce" (oscillation) can occur.
Pro-Tip: Always specify the Ceramic or Piston Damping version for gas applications. This stabilizes the float, prevents mechanical wear, and ensures the pointer remains steady for accurate local reading.
(Note: Shown for comparison; VA meters like the H250 require significantly less space than EMFs).
2026 industrial standards prioritize predictive maintenance. The H250 M40’s CFM technology detects if the float is stuck due to impurities or damaged by a pressure surge. Instead of waiting for a manual inspection to find a frozen reading, the device triggers a NAMUR NE 107 alarm via HART, allowing for immediate corrective action.
Q: Can the H250 M40 be installed in horizontal pipelines?
A: Yes. While standard variable area meters require vertical upward flow, the KROHNE H250 M40 is available in a specialized spring-loaded version. This allows for accurate measurement in horizontal or descending pipes (up to DN150 / 6"), offering maximum flexibility in tight piping layouts.
Q: Does the H250 M40 require power to show the flow rate?
A: No. One of its core advantages is the mechanical magnetic coupling system. The local pointer indicator works purely on mechanical principles, providing reliable flow readings even during a total power failure. Electronic modules like HART or fieldbus are optional and can be added later.
Q: How does the H250 M40 handle pressure surges or gas oscillations?
A: For gas applications or systems prone to pressure spikes, the meter can be equipped with ceramic or piston damping. This stabilizes the float, prevents mechanical wear, and ensures steady, accurate readings.
Q: Is this rotameter suitable for safety-critical applications?
A: Absolutely. The H250 M40 is SIL 2 certified according to IEC 61508. It is widely used in Safety Instrumented Systems (SIS) for dry-run prevention of pumps, nitrogen inertization, and coolant monitoring.
