The Cassette System was originally designed to facilitate the installation of flexible ventilation ducting in rapidly excavated headings and consist of three basic components: the fan cone, the duct storage cassette and the draw off cone. The duct storage cassette normally holds 100 m of flexible ventilation ducting and consists of an outer casing and an inner tube, the annular space between the two pieces being the storage area for the ducting. A draw off cone is attached to the inner tube to facilitate orderly pay out of the ducting and smooth airflow through the cassette unit. The third portion, the fan cone, is used to direct the air from the pressure fan through the centre cone section and remain attached to the fan when removing and installing replacement cassettes.
- Low initial cost of flexible duct and cassette system over conventional steel ducting.
- System is designed to operate at positive pressure airflows and by positioning the fans at the correct location, can be used on either fresh air in the duct or exhaust air in the duct system.
- To meet the requirements of the push-pull system with the addition of reversing switches on the fans, the total system can be designed to meet all underground ventilation codes and coal mining regulations.
- Lower labour cost to install ducting; as the boring machine extends the ducting automatically. The only labour required to install the ducting while the boring machine is in operation, is one man every 5-10 m advance to install one suspension clip on the messenger cable.
- Installation of a fully loaded cassette takes approximately 45 minutes and can be handled when preventative maintenance work is being carried out on the cutting head.
- Face ventilation is maintained at all times as the unit is close coupled to the boring machine and cannot be left 30 m back from the face as is often the case with steel duct.
- Site storage problems are eliminated as 5000 ft of flexible ducting can be stored in the open air in a space approximately 10 m x 10 m, whereas the equivalent amount of steel duct will occupy a large amount of valuable site storage space.
- Upon completion of the project, transportation of the steel duct is often uneconomical and is scrapped. Flexible ducting can be cleaned, stored and transported with minimal cost, to be used on other projects, again saving capital costs.
- Utilizes a pre-loaded container (cassette) which can be refilled on surface and taken to the workface as a complete unit, therefore requiring no extra labour underground.
- The cassette unit is totally detachable and interchangeable with replacement units. Capacity is up to 100 m (328 ft). Available in diameters from 18′ to 80”.