Roller Screens are suitable for separating fine, coarse and sticky coal. They are used in coal handling plant for preliminary screening and relief to crusher as well to ensure a clog free flow of coal.
Roller Screens Consist Of Following Parts
1. Drive Unit
The screen is driven by electric motor through gear box. Motors and gear box are connected by fluid coupling. In roller screen two drive unit are used.
2. Driven Shaft / Logitudinal shaft
They are connected with gear box by flexible coupling equipped with renewable pin bush. Two longitudinal shafts are used in roller screen, both are driven by individual drive unit. They are fitted with spherical roller bearing mounted on gear casing. The bottom portion of gear casing is partially filled with oil.
They are driven by two longitudinal shaft driving through spiral bevel gears. Each longitudinal shaft drives the alternate transverse shaft. They are fitted with spherical roller bearing mounted on gear casing.
4. Eccentric Discs roller
Roller screen consists of several single screen rollers known as eccentric discs. The eccentric discs are equipped with curved triangular discs, these triangular disc helps to avoid clogging of wet and sticky material. Individual eccentric disc are mounted on a transverse shaft. They are made of chrome molly special alloy steel.
For separation of feed materials the eccentric discs are arranged at a pre- determined distance in such a way that they form a square or rectangular opening in the screen.
They are provided below the rolls for cleaning the eccentric disc roll.
Working Of Roller Screens
When transverse shaft receive motion from two longitudinal shaft through drive unit several single eccentric disc which is mounted on transverse shaft driven in same direction. Due to rotation and special shape of the eccentric disc, materials while passing over the disc are lifted up and pushed forward towards the crusher receiving chute. The material is subjected to a gentle and harmonic rolling motion. As the material travels, the smaller particle comes to the bottom layer and passes through the opening between two consecutive eccentric disc roll. The oversized material is discharge at another end.
Work Involve During Preventive Maintenance of Roller Screens
During preventive maintenance of roller screen following equipment’s are checked step by step and detected problems are corrected.
- Fluid Coupling – Checking of fluid coupling oil quality, oil level and fusible and breather plug.
- Gear Box – Checking of oil level, oil quality, oil leakage, breather plug, teeth condition.
- Gear Coupling – Checking of teeth pitch and greasing of gear coupling.
- Gear Casing – Checking of oil level, oil quality, oil leakage.
- Eccentric disc roll – Checking the wear and tear. if the disc is wear off then hardfacing work is done on disc.
- scrapper – checking the condition of scrapper.
- Fastener – Checking the tightness of nut and bolts.
- linear plate and deflector plate – Checking wear and tear of these plates.
- Greasing – All bearing greasing is done through grease gun.
- House Keeping Status – Check Housekeeping status.
- Waste Management – Check for scrap /waste.