Krohne Variable area flowmeters H250 M40
The H250 M40 is a standard variable area (VA) flowmeter from KROHNE, designed for the process industry and OEM applications. It combines reliable mechanical measurement of liquids and gases with modern communication and diagnostic capabilities. Its unique modular design allows electronics modules to be added or replaced at any time without interrupting the process, with functionality scalable from auxiliary-power-free analog measurement to full fieldbus integration.
Key Features and Benefits
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Outstanding Modularity and Scalability: Starting from a purely mechanical indicator, users can insert limit switches, two-wire 4…20 mA/HART, counters, or fieldbus modules at any time. Modules can be replaced without tools and without interrupting the process.
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Robust Design for Demanding Conditions: The fully metal-enclosed measuring tube with no sensor penetration parts is suitable for high pressures (up to 1000 barg / 14,500 psig) and extreme temperatures (–196 to +400 °C / –320 to +752 °F). Standard wetted parts are 316L stainless steel compliant with NACE MR0175/MR 0103, with special material options including Hastelloy, titanium, Monel, and PTFE lining.
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Comprehensive SIL 2 Functional Safety Certification: Both the limit switches and the 4…20 mA analog output are certified SIL 2 by exida according to IEC 61508:2010. In redundant design (1oo2), the device can be used in SIL 3 applications.
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Advanced Diagnostics (CFM): Continuous float monitoring (CFM) comes as standard, compliant with NE 107. It detects float blockage, compression vibrations in gas measurement, pulsating flow, and external interfering magnetic fields, helping extend equipment life and improve process safety.
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Flexible Installation and Extensive Material Options: Supports vertical, horizontal, and vertical-downward pipe installation. Offers a wide range of process connections including flanges (DN15…150), threads, welding ends, clamps, and hygienic connections. A hygienic version (H250F M40) is available, compliant with FDA and EHEDG standards.
Technical Specifications (at a Glance)
| Specification | Detail |
|---|---|
| Measuring Principle | Float-type variable area |
| Measuring Range (Liquids) | Full scale 10…120,000 L/h; low-flow option from 0.15 L/h |
| Measuring Range (Gases) | Full scale 0.7…2800 m³/h; low-flow option from 1.6 L/h |
| Accuracy | ±1.6% (per VDI/VDE 3513-2, qG=50%); precision calibration optional |
| Turndown | Standard 10:1; optional 100:1 |
| Process Temperature | –196…+400 °C (–320…+752 °F) |
| Process Pressure | Up to 1000 barg / 14,500 psig |
| Wetted Materials | Standard 316L/316 dual-certified stainless steel; optional Hastelloy, titanium, Monel, 6Mo, Inconel, PTFE lining |
| Process Connections | Flange DN15…150 / ½…6″; NPT, G, welding ends, clamps, hygienic connections |
| Communication Options | 4…20 mA/HART 7, PROFIBUS PA, FOUNDATION Fieldbus, pulse output, limit switches |
| Ingress Protection | IP66/68 / NEMA 4X/6; optional IP69K |
| Ex Approvals | ATEX, IECEx, FM, NEPSI, etc.; Ex i, Ex d, Ex nA |
The H250 M40 provides a reliable, flexible, and future-proof flow measurement solution for process industry and OEM applications, thanks to its modular architecture, comprehensive SIL 2 safety certification, and broad process adaptability.
Krohne Variable area flowmeters H250 M40
The H250 M40 is a standard variable area flowmeter from KROHNE, designed for the process industry and OEM applications. It combines reliable mechanical measurement of liquids and gases with modern communication capabilities. Its modular design allows electronics modules to be added or replaced at any time without interrupting the process, with functionality ranging from purely mechanical indication without auxiliary power to full digital fieldbus integration.
The flowmeter operates on the float measuring principle. The measuring unit consists of a metal cone in which a float moves freely up and down. Fluid flows from bottom to top, and the float changes position until the lift force F1, the form drag F2, and its own weight F3 reach equilibrium (F3 = F1 + F2). The float’s height position is transmitted to the indicator or electronic sensor via non-contact magnetic coupling. Because the measuring tube is completely enclosed with no sensor penetration parts, the design can withstand extremely high process pressures, up to 1000 barg / 14,500 psig.
The core advantage of the H250 M40 is its unique modular concept. Users can start with a purely mechanical indicator version and add or replace electronics modules as needed—simply unscrew the cover, insert the module until it clicks, and screw the cover back on, without tools and without interrupting the process. Available modules include NAMUR, transistor, or reed limit switches; two-wire 4…20 mA current output with HART 7 certification; counters with LCD and pulse output; and PROFIBUS PA or FOUNDATION Fieldbus interfaces. The measuring scale can also be easily replaced to adapt to application changes.
In terms of functional safety, both the limit switches and the 4…20 mA analog output of the H250 M40 are certified SIL 2 by exida according to IEC 61508:2010, verifying not only the hardware’s random failure rate but also the system capability of hardware and software. In redundant design (1oo2), the device can be used in SIL 3 applications.
The flowmeter comes standard with continuous float monitoring (CFM) diagnostics, compliant with NE 107. CFM detects various abnormal conditions: float blockage caused by fouling or pressure surges, compression vibrations of the float in gas measurement, pulsating flow caused by positive displacement pumps, incorrect float installation after maintenance, and external interfering DC magnetic fields that could cause measurement errors. Diagnostic information is classified per NE 107, from purely informational hints to device errors that trigger a fault current output, enabling appropriate corrective measures that extend instrument life and improve process reliability.
The H250 M40 is suitable for a wide range of process conditions. Standard wetted parts are 316L and 316 dual-certified stainless steel, compliant with NACE MR0175/MR 0103. For chemically corrosive media, special materials such as Hastelloy, titanium, Monel, 6Mo, and Inconel are available; the H250C M40 model features PTFE lining for strongly acidic and alkaline applications. The process temperature range extends from –196 °C to +400 °C, with pressures up to 1000 barg. The meter supports vertical, horizontal, and vertical-downward pipe installation, with flange sizes from DN15 to DN150.
For hygienic applications in the food and pharmaceutical industries, the H250F M40 model offers an EHEDG-certified hygienic design with wetted surface roughness ≤ 0.8 μm or 0.6 μm, no dead corners or stagnation zones, CIP and SIP cleaning capability, and FDA-compliant materials.
The H250 M40 holds comprehensive global explosion protection certifications, including ATEX, IECEx, FM (USA and Canada), NEPSI (China), as well as regional approvals such as INMETRO, CCOE/PESO, KCS, and EAC. Intrinsically safe (Ex i), non-sparking (Ex nA), and flameproof (Ex d) protection types can be adapted to different regional explosion protection strategies on the same platform. The standard ingress protection rating is IP66/68 or NEMA 4X/6, with IP69K optional.
With its modular architecture, SIL 2 safety certification, CFM diagnostic functions, and broad process adaptability, the H250 M40 provides a reliable, flexible, and future-proof flow measurement solution for process industry and OEM applications.