What Is the KEC Thermal Mass Flow Meter?
The KEC is a calorimetric flow meter for gases that measures mass flow directly, with no additional temperature or pressure compensation. It is offered as the KEC-1 insertion sensor for lines from ¾" up to DN1000 and as the KEC-2 in-line version with an integrated measuring section from ½" to 3" (DN15 to DN80).
The aluminum die-cast housing and 1.4571 stainless steel probe tube are designed for demanding industrial use, with a probe rating up to 356°F (180°C) and a 1:1000 measuring span.
How the Calorimetric Measuring Principle Works
A heated PT45 sensor element is cooled by the gas flowing past it, and this cooling effect is the measurement; a PT100 measures the gas temperature at the same time. The electronics record all values digitally with a t90 response time under 3 seconds; there are no moving parts and pressure loss is negligible. Measured values are referred to DIN 1343 standard conditions, and the reference temperature and pressure are adjustable.
Measuring Range and Accuracy
Four speed versions are available: low-speed to 164 ft/s (50 Nm/s), standard to 304 ft/s (92.7 Nm/s), max to 607 ft/s (185 Nm/s) and high-speed to 735 ft/s (224 Nm/s), each starting at 0.1 Nm/s. Accuracy is ±1.5% of reading plus ±0.3% of full scale, or ±1.0% of reading plus ±0.3% of full scale with the precision calibration option. Repeatability is 0.25% of reading with correct mounting.
Full-scale volume flow depends on pipe inner diameter and gas. For air in the KEC-2, published full-scale values run from 25 cfm (45 Nm³/h) in ¾" pipe (low-speed) to 2025 cfm (3440 Nm³/h) in 3" pipe (high-speed). KEC-1 tables cover ½" through 12" pipe (DN15 to DN300) for eighteen gases and gas mixtures.
Pressure and Temperature Ratings
The probe tube is rated -40 to 356°F (-40 to 180°C) in the standard version and -4 to 248°F (-20 to 120°C) for oxygen, natural gas, propane, methane and biogas or with the silicone-free option. The display unit is rated -40 to 158°F (-40 to 70°C).
Operating pressure is 725 psi (50 bar) for the KEC-1 and 232 psi (16 bar) for the KEC-2; high-pressure versions are rated 1450 psi (100 bar) and 580 psi (40 bar) respectively. The housing is IP67.
KEC-1 Insertion and KEC-2 In-Line Versions
The KEC-1 has a G½ (ISO 228) or ½" NPT thread and sensor lengths of 160 to 600 mm (6.3 to 23.6 in). It mounts through a ½" ball valve for mounting and dismounting under pressure, and the probe tube carries an engraved depth scale.
The KEC-2 measuring section comes in G½ to G2 male thread, NPT thread, DIN EN 1092-1 PN40 flanges or ASME Class 150 and 300 flanges, and its measuring head is removable for calibration or cleaning without dismounting the section. A KEC-3 ATEX version for hazardous areas has a -4 to 248°F (-20 to 120°C) probe range.
Outputs, Power and Communication
Modbus RTU (EIA/TIA-485) is standard and transfers all parameters, in units from Nm³/h and Nm/s to kg/h and ft/min. Two galvanically isolated 4-20 mA outputs are available for flow and temperature (load 500 Ω), plus a galvanically isolated pulse output for total consumption and an alarm output rated max. 48 V DC, 0.5 A.
Power supply is 18 to 36 V DC at 5 W. Three internal counters are provided: total, freely adjustable (1 minute to 1 day) and day.
Display, Configuration and Remote Diagnosis
An integrated 2" TFT color display is optional; it shows flow, total consumption, velocity and temperature, and display and housing rotate by 180°. Inner diameter, units, zero point and leak-flow suppression, output scaling, pulse weight and Modbus settings are adjustable at the instrument or in the KEC-Soft PC service software.
Remote diagnosis over Modbus checks and changes the same parameters and reports temperature exceedances, sensor failures and the calibration date. A flow direction switch supports measurement in both flow directions.
Installation Requirements
Thermal mass flow measurement is sensitive to flow disturbances, so minimum straight inlet runs of 12 × D to 45 × D apply depending on the upstream fitting, with 5 × D outlet in every case.
The KEC-1 connection thread is tightened to 18 to 22 lbf·ft (25 to 30 Nm) and the sensor is aligned to the flow direction within ±2°. The device meets EN 61010-1, IEC/EN 61326 (EMC) and NAMUR NE 43.
Applications and Gas Types
Each KEC is configured for a specified gas, from air and nitrogen through argon, carbon dioxide, oxygen, nitrous oxide, methane, biogas, hydrogen, helium and propane, or for a customer-specified mixture. Documented applications include compressed air measurement and distribution, leakage measurement, vacuum systems, corrosive and acid gases such as biogas, gas burners, forming gas and outdoor installation.
Industries served include chemical and petrochemical, natural gas and methane, pharmaceutical, power plants, semiconductor and electronics, and automotive. Calibration options are a standard 3-point certificate (at 5 bar and 20°C), real gas calibration, a 5-point certificate and ±1% precision calibration; silicone-free and oil- and fat-free cleaned versions are available.
Common Questions about KEC - Thermal Energy Flow Meter
No. The calorimetric principle gives a direct mass flow reading, so no external pressure or temperature compensation is required. Readings are expressed at 0°C and 1013 mbar, the DIN 1343 standard state, and both reference values can be changed in the device settings.
Gases: air (L), nitrogen (N), the argon, CO2, oxygen, nitrous oxide and methane group (A), the biogas, hydrogen, helium and propane group (E), and gas mixtures (S). The A, E and S gases are named in writing at order; the E group is supplied with real gas calibration only.
The KEC-1 is an insertion probe with a ½" thread that is pushed into an existing pipe through a ball valve. The KEC-2 is an in-line meter supplied with its own measuring section in ½" to 3" sizes, threaded or flanged, so the sensor is pre-centered and aligned in the pipe by a centering screw.
The required upstream run depends on what sits before the meter: 12 pipe diameters after a slight bend, 15 after a reducer, expander, 90° elbow or tee, 20 after two elbows in one plane, 35 after two elbows in different planes and 45 after a control valve. Five diameters are required downstream in every case.
Yes, when a ½" ball valve (DN15, minimum 15 mm passage) is available at the measuring point. Where no such point exists, a ½" nipple with ball valve can be welded on with the system depressurized, or a spot drilling collar and jig can be used to drill through the ball valve on a pressurized line.
Modbus RTU on EIA/TIA-485 is standard. Two galvanically isolated 4-20 mA signals cover flow and temperature, a galvanically isolated dry-contact pulse output totals consumption at up to 50 Hz, and an alarm contact is rated 48 V DC at 0.5 A. The current outputs can be ordered active or passive, the passive type accepting 12 to 36 V DC.
The standard version holds ±1.5% of measured value plus ±0.3% of full scale; the precision version holds ±1.0% of measured value plus ±0.3% of full scale. Repeatability is 0.25% of measured value. These figures apply at an ambient temperature of 22°C ±2°C and a system pressure of 6 bar with correct mounting.
Yes. Pipe diameter, units, zero point, low-flow cut-off, 4-20 mA scaling and pulse weight can be edited on the built-in display, in KEC-Soft on a PC, or remotely over Modbus. Two settings are reserved for the PC software alone: the gas type and the standard temperature and pressure used as reference conditions.
Probe temperature reaches 180°C (356°F) in the standard version and 120°C (248°F) for oxygen, natural gas, methane, propane or biogas, or if the silicone-free option is ordered. Pressure ratings are 50 bar (725 psi) standard and 100 bar (1450 psi) high-pressure for the KEC-1, and 16 bar (232 psi) standard and 40 bar (580 psi) high-pressure for the KEC-2.