The Towa Seiden PRL-G7-25 Explosion-Proof Rotary Paddle Level Switch, manufactured by Towa Seiden Industrial Co., Ltd. (Japan), is a heavy-duty industrial point level detection instrument specifically engineered for hazardous environments subjected to violent mechanical stresses. The model integrates two critical engineering features: Japanese industrial d2G4 flameproof certification (equivalent to international Ex d IIB T4 Gb ratings) and a heavy-gauge 25A protective tube sleeve shielding the rotating drive shaft.

Key engineering hallmarks of the Towa Seiden PRL-G7-25:
1. Certified Flameproof Safety (Rating d2G4 / Ex d IIB T4): The terminal compartment housing the drive motor and microswitch assembly is cast from high-strength aluminum alloy with precision-machined flame-arresting joints. It is fully certified to withstand internal gas explosions without allowing flames, sparks, or thermal ignition fronts to propagate into surrounding flammable atmospheres, providing total compliance in Zone 1 and Zone 2 petrochemical, chemical, and solvent storage facilities.
2. Heavy-Duty 25A Protective Tube Architecture: The rotating drive shaft is encapsulated within a thick-walled SUS304 stainless steel protective sleeve (nominal pipe diameter 25A, outer diameter approx. Ø34 mm). This sleeve absorbs severe lateral bending moments, falling bulk material impacts, and heavy media subsidence forces, ensuring the internal drive shaft rotates freely without bending or mechanical binding.
3. Robust JIS 5K65A Flange Connection: Built with an industrial standard JIS 5K65A mounting flange (155 mm outer diameter, 4 bolt holes), the instrument mounts rigidly onto silo side-walls or vessel roofs, resisting continuous plant vibrations and operational shocks.

The operational mechanism of the Towa Seiden PRL-G7-25 utilizes an electromechanical torque-reaction principle with integrated motor overload protection: an internal synchronous motor turns the shaft and paddle assembly continuously at approximately 1 RPM. When rising bulk solids restrict paddle rotation, the resulting reactive torque rotates the suspended motor assembly, actuating a microswitch to trip the SPDT output contacts (250V AC, 5A) for alarm or feeder interlocking while immediately de-energizing the drive motor. This prevents motor coil overheating and burnout even during prolonged paddle burial under heavy material. Enclosed in an IP65 diecast aluminum terminal housing, the PRL-G7-25 guarantees over a decade of dependable, maintenance-free performance.

• Manufacturer: Towa Seiden Industrial Co., Ltd.
• Country of Origin: Japan
• Complete Part Number: Towa Seiden PRL-G7-25
• Product Classification: Explosion-Proof Protective Tube Type Rotary Paddle Level Switch
• Hazardous Area Approval: d2G4 (Japanese industrial flameproof standard, equivalent to Ex d IIB T4 Gb)
• Protective Construction: Heavy-gauge 25A protective tube sleeve (Pipe OD ~Ø34 mm) absorbing lateral bending and impact loads
• Operating Principle: Electromechanical torque-reaction with automatic motor cut-off
• Supply Voltage Ratings: 100V AC, 110V AC, 200V AC, 220V AC (50/60 Hz) or optional wide-range 120-250V AC / 24V DC
• Power Consumption: Approximately 2.5 W to 3.5 W
• Paddle Rotational Speed: Approximately 1.0 RPM (at 50 Hz) / 1.2 RPM (at 60 Hz)
• Electrical Output Contact: 1 SPDT microswitch (Single-Pole Double-Throw)
• Contact Current Rating: 250V AC, 5A (Resistive load)
• Detectable Bulk Density: From 0.2 g/cm³ or greater (Suitable for plastic pellets, sand, clinker, grains, and mineral powders)
• Mechanical Process Mounting: Standard Flange JIS 5K65A (Outer diameter 155 mm, 4 bolt holes on 130 mm pitch circle)
• Standard Immersion / Tube Length (L): 250 mm, 300 mm, 500 mm (Custom engineered lengths up to 1000 mm available)
• Standard Paddle Configuration: W-1 broad-vane paddle (80 x 80 mm) or folding paddle in SUS304
• Wetted Materials:
  - Shaft, Protective Tube (25A), and Paddle: Stainless Steel SUS304 (AISI 304) or optional SUS316
  - Shaft Sealing: High-performance abrasion-resistant mechanical packing seal / oil seal
• Terminal Housing Material: Heavy-duty aluminum diecast (ADC12) with flameproof enclosure integrity
• Process Vessel Operating Temperature: -10°C to +70°C (High-temperature options up to 150°C)
• Ambient Enclosure Operating Temperature: -10°C to +55°C
• Maximum Operating Pressure: Up to 196 kPa (approx. 2.0 bar / atmospheric pressure)
• Ingress Protection Rating: IP65 (per IEC/EN 60529 standard)
• Net Product Weight: Approximately 4.8 kg to 7.5 kg (depending on protective tube immersion length)