The Towa Seiden PRL-200 Series Screw-Mounted Rotary Paddle Level Switches, manufactured by Towa Seiden Industrial Co., Ltd. (Japan), combine the heavy-duty industrial endurance of the flagship PRL line with the space-saving convenience of male threaded mechanical process connections (Screw/Thread Mounting). Rather than utilizing bulky bolting flanges like the PRL-100 Series, the PRL-200 Series features precision-machined male threads (typically R 1", R 1-1/4", or R 1-1/2" PT/NPT), drastically simplifying vessel wall penetrations, minimizing fitting footprints, and enabling fast screwed installation into threaded sockets on compact process vessels.

The series is partitioned into specialized configurations:
1. PRL-200: The standard screw-mounted model (Standard Screw Type) featuring a short, balanced immersion stem, ideal for side-wall insertion on blending hoppers, feed bins, packaging funnels, and small silos handling plastic pellets, grain meal, dry sand, and bulk chemical powders.
2. PRL-200EB: Gas explosion-proof (flameproof) version certified to Ex d IIB T4 (equivalent to Japanese industrial d2G4 safety ratings). Housed in an explosion-proof diecast aluminum terminal enclosure with precision-toleranced flame paths, it guarantees complete operational safety in chemical processing bays, paint factories, petrochemical refineries, and hazardous volatile vapor zones.
3. PRL-200ED: Dust ignition-proof version engineered specifically for combustible particulate environments. Certified to prevent airborne dust explosions, this model safely monitors high-risk media such as pulverized coal, organic flour, cornstarch, wood powders, and agricultural dust clouds.
4. PRL-201: Protective tube type with screw mounting (Protective Tube with Screw Mount). The rotating drive shaft is shielded inside a heavy-wall SUS304 stainless steel protective sleeve. This rugged sheath absorbs intense lateral bending moments and falling bulk material impacts, preventing shaft deflection while preserving the agility of threaded vessel connections.

All models across the PRL-200 Series utilize an electromechanical torque-reaction mechanism with integrated motor overload shut-off: an internal low-speed synchronous motor (~1 RPM) drives the SUS304 stainless steel paddle. When rising material impedes 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 eliminates motor coil overheating and burnout even during prolonged paddle burial. Enclosed in an IP65/IP66 diecast aluminum terminal housing, the PRL-200 Series delivers unmatched durability exceeding a decade of maintenance-free service.

• Manufacturer: Towa Seiden Industrial Co., Ltd.
• Country of Origin: Japan
• Product Models Covered:
  - PRL-200 (Standard male screw/threaded mounting model)
  - PRL-200EB (Flameproof gas explosion-proof model Ex d IIB T4 / d2G4)
  - PRL-200ED (Dust ignition-proof model for combustible dust zones)
  - PRL-201 (Protective tube model with threaded process connection)
• 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 24V DC / wide-range 120-250V AC
• 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 (Multi-blade high-sensitivity paddle options available)
• Mechanical Process Connection: Male thread R 1" (PT 1") or R 1-1/2" (PT 1-1/2") (Optional NPT or G thread available)
• Immersion / Stem Lengths:
  - Models PRL-200 / 200EB / 200ED: Standard 85 mm to 250 mm (or custom specified)
  - Model PRL-201: Protective tube length from 250 mm to 1000 mm
• Wetted Materials:
  - Shaft, Paddles, and Protective Tube: Stainless Steel SUS304 (AISI 304) or optional SUS316
  - Shaft Sealing: High-grade abrasion-resistant mechanical packing seal / oil seal
• Housing Enclosure Material: Heavy-duty aluminum diecast (ADC12) with industrial protective finish
• Hazardous Area Certifications:
  - Model PRL-200EB: Flameproof / Gas explosion-proof Ex d IIB T4 (d2G4)
  - Model PRL-200ED: Dust ignition-proof (Combustible dust safe)
• Process Operating Temperature Range: -10°C to +70°C (High-temperature options up to 150°C)
• Ambient Enclosure Operating Temperature: -10°C to +55°C
• Operating Pressure Range: Up to 196 kPa (approx. 2.0 bar / atmospheric pressure)
• Ingress Protection Rating: IP65 / IP66 (per IEC/EN 60529 standard)
• Net Product Weight: Approximately 2.8 kg to 5.5 kg (depending on model and stem length)