• Dust Management Technologies

In the past, the only methods for tunnel ventilation were to input new air from the outside using a fan or to simply exhaust the inside air outside. This meant that the air inside the tunnel was not very clean. Many of the workers in this poor environment suffered from “tunnel pneumoconiosis,” and this became a big problem for society, with 1000 tunnel workers or more per year having abnormal medical findings. However, when the use of large dust collectors spread widely, later on, the previously poor work environment was improved dramatically, and the cases of “tunnel pneumoconiosis” were greatly reduced, currently to about 1/100.There is a very high concentration of inhalable particles（7.07μmand smaller)at the working face (excavation face), at 100mg/m³、with mechanical excavation and 20mg/m³ with excavation using blasting. There is also a high proportion of harmful crystalline silica, and this was a cause of tunnel pneumoconiosis. However, as a result of research and development work, our filter system is able to suck in the high concentration of dust and release the air with a cleanliness level of 0.1mg/m³, which is equivalent to the cleanliness level of the general atmosphere. Ryuki Engineering succeeded in producing compact equipment by adopting large surface area pleated filters. Even dust collectors which can process an air volume of 3000 m³ /min can be loaded onto a truck, making it possible to move them around inside the tunnel to respond to the excavation work.