SAND COOLER

Return Sand in Green Sand Foundry

Return Sand Temperature, after the vibratory shake out in a mechanised green sand foundry is around 200°c. The sand temperature is highest adjacent to the metal surface and lowest away from it. The quantity of heat to be removed depends on the sand to metal ratio and the holding time of metal in the mould. The return sand temperature at the inlet of the cooler after passing through conveyor is around 100 C. Mould of good quality and clean casting surface require well cooled sand.

Sand Cooling requires a continuous and uniform flow. To achieve the uniform flow and compensate for irregular sand supply, the sieved hot return sand is stored in a surge hopper. From there, an belt transports the hot sand to the cooling conveyor, which is designed with a perforated bottom plate. Fresh air is blown through the preparation holes and at the same time water is sprayed on to the sand from nozzles located above the conveyor. Vibrations of the conveyor and turbulence caused by the air blown through ensure that sand water mix well so that the water evaporates and the sand is cooled. The belt, the cooling conveyor, and the sand spraying unit are controlled by level indicators located in the surge hopper. The plant operates only if the sand in the surge hopper is between the maximum and minimum level.

Sand Moistening

Sand temperature are measured at the entrance of the cooler and in the third stage of the cooler. An electronic thermometer controls the amount of water sprayed in several steps. Depending on the values, measured, a variable number of spraying nozzles is engaged or disengaged. This ensures exact dosage of the water required for cooling and moistening. The nozzle units are engaged automatically in steps depending on the sand temperature.

Salient Features

• Cooling system ensure constant temperature and moisture at the return sand.
• Low maintenance due to absence of moving parts.
• Quick cooling by double effect water and air cooling.
• Sand movement effected by the fluidization property of sand and vibratory motion.
• Balanced draft system ensures negative pressure above the bed.
• Environment friendly.

Benefits

• Substantial reduction in rejection of castings.
• Saving in conversion cost of rejected castings
• Substantial saving in bentonite consumption.
• Excellent surface finish of castings.
• Increased productivity.
• No oolite formation occurs in mulling.
• Continuous on-line use of return sand.
• Ease of maintaining permeability and hardness of the mould.
• Saving in man power cost.