Fork-11 Explosion-Proof Tuning Fork Level Switch
The Fork-11 Explosion-Proof Tuning Fork Level Switch is the perfect solution for measuring the presence of powdery and fine-grained bulk solids across a wide range of media and Explosion-Proof applications.
The Fork-11 Explosion-Proof and Intrinsically Safe Tuning Fork Level Switch is a highly reliable point level detection device specifically designed for powdery and fine-grained bulk solids in hazardous environments involving both flammable gases and combustible dusts.
With updated dual explosion protection certifications—Flameproof (Ex db IIC T1~T6 Gb; Ex tb IIIC T80℃~T440°C Db) and Intrinsically Safe (Ex ia IIC T1~T6 Ga; Ex ia IIIC T₍₂₀₀₎100℃~T₍₂₀₀₎450°C Da)—the Fork-11 is fully compliant for use in Zone 0/1/2 (gas) and Zone 20/21/22 (dust) hazardous areas.
Engineered with robust construction and advanced filtering algorithms, it resists false triggering from dust, vibration, or low bulk density. Its compact design allows for easy installation in silos, bins, and hoppers, making it ideal for industries such as cement, power, chemical, and food where explosion risks are present.
The probe of Fork-11 Explosion-Proof Tuning Fork Level Switch is based on a tuning fork harmonic resonance. It utilizes piezoelectric devices to drive the fork to vibrate and detect the changes of vibration. T
he fork vibrates in resonant frequency when it is in air. Once the fork comes into contact with application medium, the vibration amplitude of the fork will decrease substantially. Output from the detecting piezoelectric device will decrease accordingly. An integrated circuit is designed to analyze the amount of decrease and output a switch signal. By reasonably increasing the area of tines and precisely adjusting harmonic resonance, Jiwei Fork-11 Explosion-Proof Tuning Fork Level Switch offers great reliability and sensitivity. Therefore, it makes Fork-11 the best level switch for ultra-low-density media.
● Certified Safety: With CE Certificates, Gas/Dust Flameproof Enclosure (Ex db lIC T1…T6 Gb; Ex tb IIIC T80℃…T440°C Db) and Gas/Dust Intrinsic Safety (Ex ia II CT1…T6 Ga; Ex ia IIIC T₂₀₀100℃…T₂₀₀450℃ Da) Certificates, and IP66/IP67 Ingress Protection.
● Ultra-Light Powder Detection: Accurately measures solids with bulk density as low as 0.008g/cm³, including flakes and light powders.
● Anti-Buildup Design: Optimized tine shape and resonant frequency reduce false switching and material adhesion.
● Tall Silo Adaptability: Suspension cable version enables flexible use in deep or narrow silos.
● High Temperature Resistance: Operates in process temperatures up to 400°C, suitable for extreme heat conditions.
● Robust Diagnostics: Built-in self-check function quickly identifies and reports faults for reliable operation.
● Hygienic Compliance: Meets FDA, HACCP, and 3A standards, ensuring safe use in food and pharmaceutical industries.
● Corrosion Resistant: 316L stainless steel wetted parts offer excellent resistance to aggressive media.
● Easy to Use: Tool-free installation, with zero maintenance design for long-term stability.
| Applicable medium | Types of the Medium | powders or granular solids |
| Density | ≥0.008 g/cm³ | |
| Medium size | Max. 10mm | |
| Probe data | Vibration frequency | ～140Hz |
| Fork length | 150mm | |
| Switching Delay | When immersed | 0.5s |
| When laid bare | 1s | |
| Power supply | Relay | 20～253V AC/20～72V DC |
| Two-wire | 10～36V DC | |
| Max. power consumption | 8VA(AC)；1.5W(DC) | |
| Output | Relay | DPDT, 5A/253V AC/24V DC |
| Two-wire | 8mA/16mA， Alarm <2.3mA | |
| Installation conditions | Process pressure | -1～25bar |
| Process temperature | Regular temperature r: -50～150℃ High temperature: -50～250℃ Ultra-high temperature: -50～400℃ | |
| Ambient temperature | -40～80℃ | |
| Storage and transport temperature | -40～80℃ | |
| Cooling system data (for Ultra-high temperature only） | Air intake tube | 6×4 (Outer diameter 6mm) PU tube |
| Cooling air pressure | 0.8Mpa | |
| Min. cooling air flow rate | To be adjusted | |
| Overvoltage protection | Relay | Category III, class I |
| Two-wire | Category III, class II | |
| Certificates and approvals | Ingress Protection | IP66/IP67 |
| Explosion-Proof | Flameproof Enclosure:： Ex db lIC T1…T6 Gb; Ex tb IIIC T80℃…T440°C Db | |
| Intrinsic Safety： Ex ia II CT1…T6 Ga; Ex ia IIIC T₂₀₀100℃…T₂₀₀450℃ Da | ||
| CE | LVD and EMC Certificates | |
| Materials | Housing | Aluminum alloy, stainless steel |
| Ground terminal | 316L | |
| Process fitting | 316L, 316L coated PTFE | |
| Fork | 316L, 316L coated PTFE | |
| Process seal | Klingersil C-4400 |
● Hazardous Area Use: Ideal for chemical plants and other explosive environments. Certified for Ex db IIC T1~T6 Gb, Ex tb IIIC T80~440°C Db, and Ex ia IIC/IIIC.
● EPS/EPP Materials: Stable level detection in foam molding and plastic forming machines.
● Zircon Sand & Petroleum Coke: Handles abrasive or cohesive solids with strong anti-buildup capability.
● Ultra-Low-Density Powders: Detects materials with densities as low as 0.008 g/cm³, including dust and insulation powders.
● Fumed Silica (SiO₂): With PTFE coating, Fork-11 is ideal for detecting fumed silica (0.01 g/cm³), preventing buildup and false switching.
