Features: Non-sealed D41W manual ventilation valve. The valve can be used as a two-way pipeline hoist and ventilation and dust control apparatus, being used in metallurgy, mining, cement, chemical, power generation waiting for the industry and environmental protection systems of ventilation and dust. Features: This valve is welded steel, length short, light weight, simple structure, easy maintenance, the electric field operation and can achieve remote control. The valve is non-sealed valve.