Q. Illustrate Moisture content test ?
Moisture content test: Moisture is an important constituent of moulding sand. Its content in the moulding sand can be estimated as given below:-
By the loss of weight after evaporation: Test sample is carefully weighed 50 gm of moulding sand. It is heated for 2 hours at 1050c to 1100c. It is then allowed to cool to room temperature on a desicator, after which it is reweighed. The difference in weight divided by the weight of the sample and multiplied by 100 give the percentage of moisture content.
By moisture teller: A in this method, the sample is placed on the teller pan which has 500 mesh screens in the bottom. Hot air is blown through the sand. Moisture gets removed in only about 5 minutes and so the method is quite fast. The sand sample is weighed directly in the teller pan, and the loss in weight is accordingly determined.
By moisture teller based on chemical reaction: In this method, a measured weight of sand (10 gm) in a cap is placed in the moisture teller along with a container containing a measured amount of CaC2. The reaction of CaC2 with moisture in the sand will produce C2H2,
CaC2 + 2H2O → C2H2 + Ca(OH)2
The amount of C2H2 produced is proportional to the content of moisture in the sand. The moisture content is directly measured from a calibrated scale on the instrument.