An NH profile rotor is employed. This rotor has been developed through an analysis of the thermal deformation of screw rotors in operation. By maintaining the optimum gap between screw rotors in operation. The leakage of air has been dramatically reduced. As a result, overall adiabatic efficiency has been improved 5% compared with that of a conventinal compressor, for reduced operating costs and newly developed resin coating (patent pending) is applied to the surface of the rotor, significantly increasing its durability. In addition, highly accurate grinding technology and precision profile measuring technology contribute to the superior quality of the rotor.
Typical calculation for model SDS-T170(170kW) (For example : in the case of our conventional compressor. operating cost, when calculated at 15 yen/kWh, is ¥15 million per year.)
Maintenance cycles of compressors vary depending upon the life of the roller bearings that support the screw rotor. In the development of this T series, the latest analysis technology and lubrication theory were drawn upon. They were applied to selecting lubricating oil, improving the purity of the oil, and determining the shape of the injection nozzle including selecting materials for the bearings with a view to enhancing dimensional accuracy. Long life was realized by controlling all the components in optimal conditions. The latest technologies are reflected in features such as high-endurance floating seals and a newly developed resin coating. The regular maintenance cycle of 35,000 hours or four years in the case of a conventional Hitachi model has been lengthened to 50,000 hours or six years in the T series, for the reduction of maintenance costs.
Comparsion of maintenance costs (including the costs of maintenance of accessories and of overhaul) between model SDS-T170 and a conventional compressor (the maintenance cost of a conventional compressor being 100)
Measures taken go beyond ordinary maintainability
Fully opening double doors close to become an effective soundproof cover. this design feature not only reduces noise, but also dramatically improves the maintainability of the unit. High-grade anti-rust paint is applied to the internal surfaces of the casing and aircooler, and valves made of rust-resistant material are used for improved durability and reliability — all to reduce maintenance costs.
Capacity is adjusted with two-step control; loading and unloading are controlled based on increases and decreases in air consumption detected by discharge pressure changes. The pressure that triggers loading and unloading is set with specified margins on each side of the operating pressure. Since a loading and unloading cycling inverval can be short (a minimum of 30 seconds), only a small receiving tank is needed. The capacity control valve is a simple structure with a hydraulic piston driving a rack and pinion, ensuring sure switching without malfunctions caused by rust.
Long-duration floating seals enable the compressor to be operated with minimal air leakage for an extended time. Visco-type seals and labyrinth seals are also used in the bearing section, providing a double barrier against oil mist entering the compression chamber.
The air filter uses two types of unwoven cloth of synthetic fiber, arranged in three dimensions.The laminated structure of this filter takes advantage of the dust collectiong properties of the cloth, to capture particles in a multi-directional structure. Easy cleaning means the filter can be used repeatedly. Since the filter is also readily installed and removed, maintanace time is reduced.
This valve prevents dischanged air from flowing backwards during unloading. It is a lift type widely used as a reciprocating compressor cylinder valve.Its structure, with fewer moving and sliding sections, assures high reliability even after one million opening and closing cycles.