Guiyang.bai@honno-auto. com
86-13840589744
Rotary paddle level switch for powder, granular and block solids in silos and hoppers; SPDT micro switch 5 A / 250 VAC, up to 1300 °C, IP65/66/67.
The HNL40-A rotary paddle level switch uses a micro motor and clutch to drive a measuring paddle. When the blade contacts the material, the motor stalls through the clutch, the micro switch actuates and outputs a contact signal, and motor power is cut off. When the material clears the blade, spring tension resets the switch and the paddle resumes rotation. It monitors full, set-point and empty level in solid-material silos and hoppers.
The switch suits powder, granular, adhesive and block solids in silos, hoppers, scales and discharge pipelines. It is widely used in metallurgy and casting, grain and flour milling, feed and fertilizer, building materials and cement silos, coal handling and power plants, chemical and plastics processing, pharmaceutical powder handling, food powder manufacturing, environmental dust-removal systems, material transport and control processes, and injection-molding machine material buckets.
Good fit: solid material silos and hoppers, metallurgy and casting, grain and flour milling, feed and fertilizer production, building materials and cement silos, coal handling and power plants, chemical and plastics processing, pharmaceutical powder handling, food powder manufacturing, environmental dust removal systems, scales and discharge pipelines, material transportation and control processes, injection molding machine material buckets.
Choose HNL40-A when:
You need a point level (full / empty / set-point) signal for powder, granules, pellets or block solids under normal pressure.
The bulk density meets the rated ≥0.3 g/cm³ or ≥0.5 g/cm³ blade version, and dust, dielectric constant, adhesion, temperature or pressure variation does not affect a paddle-type detection.
A simple SPDT micro-switch contact to a PLC or alarm relay is acceptable.
Confirm with us first when: the material is a free-flowing liquid, extremely low density or strongly cohesive; the silo is pressurized; the required temperature exceeds the selected high-temperature range; or the medium is abrasive and needs a shaft protection tube or steel-cable version.
A low-speed gear motor with a sliding clutch drives the rotating paddle. When the material obstructs the paddle, the motor turns against the clutch, the internal micro switch actuates and outputs the detection signal, while motor power is cut off. Once the material is no longer present, the blade obstruction is released and internal spring tension resets the switch; power returns to the motor and the paddle rotates again.
The friction clutch slips instead of forcing the motor when the paddle stalls, protecting the motor. The mechanical seal keeps dust out along the shaft. Torque is adjustable on the torsion spring: a weaker-hole setting raises sensitivity for low specific gravity; a stronger-hole setting lowers sensitivity when torque is insufficient.
The simple mechanical principle and modular construction suit continuous silo duty, with multiple process connectors, optional extensions, high-temperature and steel-cable versions.
| Model | HNL40-A — Rotary paddle (resistance rotary) level switch for solids |
|---|---|
| Power supply | 110 VAC / 220 VAC / 24 VAC / 24 VDC, 50/60 Hz |
| Signal output | Micro switch 5 A / 250 VAC, SPDT |
| Blade speed | 1 r.p.m. |
| Electrical connection | M12×1 5-pin / 8-pin aviation cable |
| Shaft length combinations | 100–2000 mm / 100–1500 mm / 300–3000 mm / 450–6000 mm / 100–6000 mm / 450–1500 mm / 80–1000 mm |
| Working pressure | Normal pressure |
| Temperature range | –20…80 °C / –20…350 °C / –20…1300 °C / –40…350 °C / –20…250 °C, or customizable |
| Connections | Thread G1" / G1-½" (customizable); flange 2-½" × 5 kg/cm² (customizable) |
| Applicable bulk density | ≥0.5 g/cm³ or ≥0.3 g/cm³ (per blade version) |
| Blade | Type A / Type B per blade specification table (customizable) |
| Junction box material | Aluminum alloy baked paint / PEK / stainless steel |
| Protection level | IP65 / IP66 / IP67 |
| Micro switch | 125–250 VAC 5 A; mechanical life ≥2 million cycles; electrical life 10,000–100,000 cycles; contact resistance ≤30 MΩ; insulation resistance ≥100 MΩ @500 VDC; ambient –25…+120 °C; humidity 85% RH; IP67 |
|---|---|
| Micro motor | AC200–240 V 50/60 Hz (or custom by contract); clockwise; 0.8 rpm (50 Hz) / 1.0 rpm (60 Hz); torque 25 kgf·cm; ambient –20…+80 °C; ≤4 W |
| Code segment | Code | Description |
|---|---|---|
| Product type | 10 / 11 | Standard thread / standard flange type |
| 20 / 21 | Flange shaft protection tube / adjustable flange shaft length type | |
| 30 / 31 / 32 / 33 | High-temperature thread, flange, flange protection tube, ultra-high-temperature flange protection tube | |
| 40 / 41 / 42 | Steel-cable / high-temperature steel-cable / high-temperature adjustable flange shaft length type | |
| 980D / 50 / 60 | Explosion-proof type / indicator-light type / cement-silo special type | |
| 80 / 80A / 80C | Standard small-resistance rotation / high-temperature low-resistance / flange protection tube small-resistance rotation | |
| Power supply | A | 110 VAC |
| B | 220 VAC | |
| C | 24 VAC | |
| D | 24 VDC | |
| Connection | – | Thread A ¾"–J 6"; flange D 2"–J 6"; PT(R), NPT, BSP, sanitary clamp, 150/300 lbs, PN10/16/25/40, 5/10 kg/cm², special on request |
| Blade | A–H | W×H 100×30 / 65×80 / 60×30 / 80×35 mm; sickle, double-folding, single-folding, cross-bonding |
| Shaft length | – | Four digits, unit mm |
Mount through the silo wall or roof so the blade sits in the material path and contacts the powder at the target level. Respect the material resting angle; ensure the blade reaches the powder, especially for upper-limit alarms. Avoid dead corners near the hopper bottom and stay clear of bridge-breaking equipment. If powder deposits more than 1 m from the switch, provide suitable protective equipment; when filling directly against the switch, install a protective plate to prevent the material from striking the head. The terminal block provides power supply, NC, COM and NO; the SPDT contact switches between NC (unloaded) and NO (loaded) per the control circuit.
Cement and building materials: silo full / empty detection and level control.
Grain, feed and fertilizer: hopper and bin point-level monitoring.
Chemical and plastics: powder, pellet and granule hoppers, injection-molding machine buckets.
Metallurgy, coal and power: hoppers, scales and discharge pipelines; high-temperature versions for elevated material temperature.
Send: material and bulk density, material temperature, silo/hopper size and available opening, required shaft length, mounting style (thread / flange / protection tube / steel cable), power supply, required contact logic, and any dust or abrasion conditions. We will confirm the product type, connection, blade and selection code before quoting.
Can it detect powders and granules?
Yes. The paddle switches on when the material obstructs rotation; blade versions cover bulk density ≥0.3 g/cm³ and ≥0.5 g/cm³. Low-density powders may need the weaker-spring higher-sensitivity setting and a small blade.
How does the paddle maintain reliable point detection inside dusty silos?
Paddle detection is not affected by dust or dielectric constant, and the integrated shaft seal keeps dust out along the axis. The clutch slips on stall to protect the motor; the modular design is maintenance-free in normal duty.
Will sticky solids obstruct rotation and delay the empty-level signal?
Adhesive or caked material can bind the paddle and delay reset. For sticky duty, keep the blade path clean, choose a suitable blade, or consider the low-resistance rotation versions; confirm material behavior with us before ordering.
Where should the paddle sit for high-level overflow prevention?
Mount the high-level switch so the blade contacts the powder at the alarm level, respecting the resting angle and avoiding dead corners. For roof mounting, account for shaft length and any protection tube or steel cable.
What maintenance protects the shaft seal from abrasive dust?
The sealed shaft and clutch reduce dust ingress; inspect the seal and paddle periodically in abrasive service. Use a protection-tube or steel-cable version where abrasion or long shaft length calls for extra protection.
HNL40-A Rotary Paddle Level Switch Datasheet (PDF) — view all product manuals on our Download page »
Send us the material, density, temperature and opening. We will confirm the mounting, blade and selection code before we quote.
Send us your application details »
Contact: HongNuo
Phone: 13840589744
Tel: 86-13840589744
Email: Guiyang.bai@honno-auto. com
Add: Zhongguancun Innovation Center, No. 28 Huahai Road, Shenyang Economic and Technological Development Zone, Liaoning Province
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