KAL-K - Thermal Flow Switch with LED Flow Trend Indication for Water-Based Liquids

The KOBOLD KAL-K is a thermal flow switch for water-based liquids that uses microprocessor-based temperature compensation to keep its switch point accurate as process temperatures change. It detects flow velocities from 0.2 to 6.6 feet per second (0.06 to 2 meters per second) across an operating range of 32 °F to 250 °F (0 °C to 121 °C), with CIP compatibility up to 280 °F (138 °C) in non-operating mode. Manufactured in Pittsburgh, USA, this compact one-piece unit combines proven calorimetric measurement with rugged stainless steel construction and a solid-state design that eliminates temperature-related reading drift. Response times run 5.6 seconds typical, or 2 seconds with the optional fast-response version.

How Does the KAL-K Thermal Flow Switch Work?

The KAL-K operates on the time-proven calorimetric principle: an internally heated probe extends into the flowing media, liquid moving past the sensor carries heat away, and the microprocessor converts the resulting cooling rate into a flow reading. Because cooling accelerates as velocity increases, the electronics switch reliably at a user-selected flow threshold.

During each measurement cycle, the system records the ambient liquid temperature, heats the probe for 0.8 seconds, then monitors the cooling rate over the following second; the probe returns to ambient within 5.6 seconds, ready for the next cycle. The microprocessor compares each cooling rate to an internal temperature-specific lookup table, automatically compensating for ambient temperature changes that would otherwise cause measurement errors. Unlike conventional thermal dispersion flow switches that experience reading drift across temperature variations, this intelligent compensation maintains consistent switching behavior through process heating and cooling cycles. To learn more about the advantages and limitations of this measuring principle, visit our in-depth article about thermal flow technology.

No Moving Parts Design for Long-Term Reliability

A solid-state sensor with no mechanical components eliminates the wear-related failures common in paddle and flap style flow switches. The compact probe creates negligible pressure loss and remains insensitive to dirt and particulate matter, making the KAL-K well suited for continuous monitoring in industrial water systems, cooling circuits, and many other process applications.

Materials, Fittings, and Pressure Ratings

Available wetted materials include 304 stainless steel and 316-Ti stainless steel for NPT threaded connections, and 316L stainless steel for the sanitary Tri-Clamp version. Installation options span 1/2 inch NPT, 3/4 inch NPT, and 1-1/2 inch Tri-Clamp fittings, with maximum pressure ratings of 1450 PSIG for threaded versions and 600 PSIG or per clamp rating for Tri-Clamp models.

Model designations follow the fitting and material: KAL-4215 (1/2" NPT, 304 SS), KAL-4315 (1/2" NPT, 316-Ti SS), KAL-4320 (3/4" NPT, 316-Ti SS), and KAL-4340S (1-1/2" Tri-Clamp, 316L SS). Available options include an extended probe, fast response time, N/C switch logic, a plug connector with cable, and a 110 VAC version with dry contact. The IP 65 rated housing protects the electronics in washdown environments while maintaining easy access to controls and indicators.

3-A Compliant Sanitary Flow Monitoring

The sanitary KAL-K carries 3-A authorization (Certificate 28-05) and is specifically engineered for food processing, dairy, beverage, and pharmaceutical manufacturing applications. Its 1-1/2 inch Tri-Clamp connection and hygienic 316L construction meet strict sanitary design standards, and the non-operating CIP rating accommodates clean-in-place cycles without removing the switch from the line.

Field Calibration and Intuitive Operation

A straightforward five-minute setup procedure adapts the device to specific liquid properties and operating ranges directly in the field — no bench equipment required. Zero-flow and span calibrations start from a single SET pushbutton, and the setpoint potentiometer positions the alarm threshold anywhere along the measuring range.

The integrated 8-segment LED bar graph provides visual flow trend indication, while the bi-colored status LED clearly shows alarm conditions in red and normal flow in green. Power options include 24 VDC with switch-selectable PNP or NPN semiconductor outputs, or a 110 VAC version with normally open dry contact relay output. The alarm setpoint is fully configurable as normally open or normally closed to match existing control logic.

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