Is HNF10-E the right choice for your application?

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

• Pipe nominal diameter is DN25 or larger, and mechanical flow/no-flow detection is required without continuous flow reading.

• The medium is water, oil, air or inert gas, with typical cleanliness and acceptable levels of suspended solids.

• SPDT single-pole double-throw contacts are needed, providing both normally open and normally closed signals for alarm and interlock duty.

• A purely mechanical structure is preferred for simplicity, high reliability and no power supply or electronic maintenance.

• Multiple pipe sizes are present on site and adjustable baffle combinations are needed to match different trip flows.

• Cost-sensitive high-volume deployment is planned, with consistent switching repeatability required.

Please consult us first if: pipe size is below DN25, medium is highly viscous, line pressure exceeds 16 bar, corrosive media need special materials, IP67 housing is required, or analogue / communication output is needed.

Why choose a mechanical paddle flow switch

SPDT dual-contact output for flexible control

Integrated SPDT microswitch provides both normally open (NO) and normally closed (NC) contacts, allowing simultaneous running status feedback and fault alarm for various control and interlock circuits.

Large pipe coverage, wide flow range

Designed for DN25 and larger pipes. By combining different baffle sizes, one unit covers multiple pipe diameters and flow ranges, reducing spare part variety on site.

Five baffles included, field-adjustable

Five baffles of different sizes are supplied as standard. They can be freely combined on site to match actual pipe size and required trip flow, no additional ordering needed for commissioning flexibility.

Mechanically isolated, dirt-tolerant and robust

The wetted mechanical part and electrical switch are fully isolated so liquid cannot enter the switch compartment. The paddle design resists fouling and jamming in typical cooling and circulating water for long-term reliable service.

Technical Specifications

Installation & Commissioning

Confirm 4 items before ordering:

1. Pipe nominal diameter and medium type – to confirm compatibility and pre-select baffle combination.

2. Required trip flow – can be factory-preset or adjusted on site.

3. Medium temperature and line pressure – to verify seal and body material compatibility.

4. Protection class and microswitch grade – standard IP33 or upgraded IP67, domestic or imported switch.

Install vertically on a straight pipe section with the baffle plane at 90° to the flow direction. The baffle must not rest against the pipe wall, as this will cause false tripping. Avoid disturbed flow downstream of valves, elbows and pump outlets. After wiring, verify the switch trip point under actual flow conditions; adjust baffle combination as needed. Confirm NO/NC logic matches your control circuit before commissioning.

Outputs & System Integration

• SPDT microswitch output: single-pole double-throw contacts with both normally open (NO) and normally closed (NC) for running status feedback and fault alarm interlock, directly connectable to relays, contactors or PLC digital inputs.

• Full mechanical-electrical isolation: wetted side and electrical side are completely separated by the seal assembly, improving electrical safety in damp and conductive media environments.

• Passive contact, no power required: purely mechanical passive switch signal with no separate power supply needed, simple wiring and compatible with various traditional control circuits.

For OEM volume projects, please specify pipe size, medium type, target trip flow, mounting orientation and microswitch grade with your enquiry so we can factory-preset parameters and match the correct configuration.

Typical Applications

Large-bore cooling & circulating water systems

Used in central air-conditioning, industrial cooling towers and heat-exchange stations to monitor water flow and trigger alarm or standby pump start on flow loss, protecting heat exchangers and main equipment.

Air compressors & pneumatic systems

Installed with air compressors, compressed air networks and pneumatic systems to detect gas line flow status for compressor protection and air-supply abnormality monitoring.

Industrial pump protection

Mounted on pump discharge to verify that effective flow is established, triggering protective shutdown on suction loss or line blockage to prevent pump dry-running damage.

Refrigeration & air-conditioning units

Water flow monitoring in chillers, cold-water units and heat pump systems to maintain heat-exchange efficiency and prevent evaporator / condenser faults from insufficient water flow.

Water treatment & process water circuits

Provides flow on/off signals in water treatment plants, filtration systems and process water lines for process interlocking and abnormality alarming.

Information Required for Selection

To confirm the correct HNF10-E configuration, please provide: pipe nominal diameter, medium name & temperature range, target trip flow rate, mounting orientation & line pressure, body material preference (brass / stainless steel), protection class requirement (standard / IP67) and microswitch grade preference. For viscous media state the viscosity; for gaseous media state pressure and temperature.

Frequently Asked Questions

Which pipe sizes accept this paddle switch?

It is designed for pipes DN25 and above. By combining different baffle sizes from the supplied set, it covers a wide range of pipe diameters and flow ranges.

Can the five supplied baffles be combined on site?

Yes. Five baffles of different sizes are included as standard. They can be freely assembled on site to match actual pipe size and required trip flow for flexible commissioning.

Does it provide an SPDT microswitch output?

Yes. It has an integrated SPDT single-pole double-throw microswitch with both normally open (NO) and normally closed (NC) contacts, rated at 250 VAC / 3 A.

How much average pressure loss occurs at the maximum rated flow?

Average pressure drop is approximately 0.08 bar at maximum rated flow, adding very little system resistance – well suited to cooling and circulating water circuits sensitive to head loss.

What housing option raises protection from IP33 to IP67 for harsh installations?

An optional IP67-rated housing is available for damp, splash-prone and harsh installation environments. Standard version is IP33; please specify IP67 when ordering.

Downloads

HNF10-E Paddle Flow Switch Datasheet (PDF)

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