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Question

Permeability of a foundry sand is:

A.

Porosity to permit the escape of gases/air

B.

Fineness of sand

C.

Distribution of binder in sand

D.

Capacity to hold moisture

Answer ( Option A)

Porosity to permit the escape of gases/air

Solution

Permeability of a foundry sand is the porosity of sand to permit the escape of gases/air. It is expressed by permeability number (Pn) as follows.

           

Where,V = Volume of air passing through the specimen.

H = Height of cylinder specimen

P =   Difference of pressure of air passing through the specimen ( gm/cm2)

A=   Area of cross-section of specimen

T= Time taken by air to pass through the specimen (in minutes)

            

Hence, the correct option is (A).

&Key Points:-

Generally, permeability number lies between 60 and 120.

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