Is HNF10-AC the right choice for your application?

Select this model when all of the following conditions are met:

• You need to monitor flow / no-flow of liquids (water, oils, cutting fluids) or gases (compressed air) in a pipe.

• The set velocity falls within 1–150 cm/s water, 3–300 cm/s oil, or 20–2000 cm/s air.

• You need a switching output (PNP/NPN or relay NO+NC) directly into a PLC or alarm circuit.

• Medium temperature is −20…90 °C, ambient −20…80 °C, and pressure ≤ 100 bar.

• You prefer no moving parts, maintenance-free operation, and all-304-stainless construction for industrial, wet environments.

• You want one model covering many pipe sizes, with on-site potentiometer set-point adjustment.

Please consult us first if: medium temperature exceeds 90 °C, pressure exceeds 100 bar, explosion-proof rating is required, the medium needs special wetted materials, or you need a 4–20 mA analogue flow output rather than a switching signal.

Why choose the HNF10-AC thermal flow switch

Gas-liquid dual-use, one instrument, many media

The same unit monitors water and oils as well as compressed air. Wide set ranges – water 1–150 cm/s, oil 3–300 cm/s, air 20–2000 cm/s – reduce spare-part variety.

No moving parts, maintenance-free

Based on heat exchange, the probe contains only heating and sensing elements – no rotating or sliding parts, no wear, no sticking, no drift. Repeatability ±0.5%, long-term maintenance-free.

All-304 stainless steel, 100 bar pressure rating

Both probe and housing are 304 stainless steel, pressure-rated up to 100 bar, IP67 – suitable for hydraulic systems, high-pressure cooling water and wet industrial sites.

LED status, on-site potentiometer set point

Red LED = no flow or below set point; green LED = above set point. Adjust the front potentiometer to set the switch point; after about 2 s initialisation it is ready, response 1–6 s (typ. 1 s).

Technical Specifications

Installation & Commissioning

Installation notes:

1. Before installation confirm the switch matches the system and the fitting thread – mismatched threads can damage the product.

2. Protect the M8 plug and the bottom probe from impact; keep the sealing face and measuring point clean and undamaged.

3. For vertical mounting, install on a section flowing upward; for horizontal mounting, orient the probe away from air pockets and sediment.

4. The sensing point must be fully wetted with medium, otherwise reading is inaccurate; tighten with the specified torque.

Setup: After power-on, the unit initialises (green LED on for about 8 s, then red). Once flow is established, turn the potentiometer: anti-clockwise 2–3 turns until red, then clockwise until it flips to green – the switch point is set.

Outputs & System Integration

• PNP / NPN: max 400 mA, direct to PLC digital inputs.

• Relay: max 1 A / 48 V AC-DC, NO+NC selectable, direct to alarm lights, contactors or interlock circuits.

• Electrical protection: reverse-polarity, short-circuit and overload protection – rough wiring on site is unlikely to damage the unit.

• M8 connector: quick plug/unplug for factory assembly and field replacement.

For factory pre-calibration against a specific medium and flow set point, please send us the medium name and target switching velocity at inquiry time.

Typical Applications

Circulating & cooling-water flow monitoring

Real-time flow detection in industrial circulating water and equipment cooling loops – flow loss triggers the alarm contact and interlocks shutdown to prevent overheating.

Cutting fluid & lubricating oil dry-run protection

Monitors low flow of machine-tool cutting fluid and hydraulic lubricating oil to protect tools and pumps from oil-loss wear.

Pump dry-run protection

Installed at pump inlet/outlet piping; when the medium disappears or flow drops below threshold, the alarm trips and prevents pump burnout.

Pneumatic & hydraulic systems

Gas-liquid dual-use design covers both compressed-air lines and hydraulic oil circuits, monitoring gas flow and oil circulation status.

Petrochemical, power, metallurgy & battery plants

Widely used in petrochemical, power, metallurgy, steel, papermaking, food processing, water treatment and battery production for process piping and compressor protection.

Information Required for Selection

To confirm the correct HNF10-AC configuration, please provide: medium name (water/oil/air/other), target switching velocity or flow, medium temperature, pipe pressure and thread, required output (PNP/NPN/relay, NO/NC), and ambient temperature. For factory pre-calibration, also send the medium and the specific flow range.

Frequently Asked Questions

Which water, oil and air velocities are adjustable?

Water 1–150 cm/s; oil 3–300 cm/s; air 20–2000 cm/s. The on-site potentiometer sets the switch point within these ranges.

Can one switch monitor both gases and liquids?

Yes. HNF10-AC is gas-liquid dual-use: based on heat exchange, the same unit monitors water, oils and compressed air.

Does the relay provide both NO and NC contacts?

Yes. The relay version offers NO + NC contacts up to 1 A / 48 V AC-DC, suitable for different alarm and interlock logic.

How does the thermal principle provide flow detection without any moving parts?

The probe contains heating and sensing elements: with no flow the sensor reads a fixed heat level; with flow the heat is carried away and the temperature difference is converted into a switching signal – purely electronic, no mechanical parts.

What pressure and temperature limits apply to the stainless steel probe?

Both probe and housing are 304 stainless steel, pressure-rated 100 bar, medium temperature −20…90 °C, ambient −20…80 °C, protection IP67.

Downloads

HNF10-AC Thermal Flow Switch Datasheet / Manual (PDF)

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