Production Technology Laboratory Lab Experiments

Testing of Permeability Experiment

Oct 21 2023

Objective

Testing of Permeability

Equipment Required

Sand Specimen (5.08 mm diameter and 50.8 mm height)
Permeability Meter

Overview:

Permeability is that property which allows gas and moisture to pass through the moulding sand. It is determined by measuring the rate of flow of air through A.F.S. standard rammed specimen under a standard pressure. The volume of air in cm3 / min. passing through a specimen of length 1 cm. and cross sectional area of 1 cm2 under a pressure difference of 1 cm. water gauge is called Permeability Number. The volume of air passing through a sand specimen 1 sq. cm area and 1 cm. in height at a pressure of 1 gram per square centimeter in 1 min. is called the Permeability Number and is computed by the formula:

Where,

P = Permeability Number

V = Volume of air passing through the specimen (cubic centimeter or in mil)

H = Height of specimen (centimeters)

p = Pressure difference between upper and lower surfaces of test specimen (in centimeter of water column)

A = Cross-sectional area of specimen (square centimeter)

t = time (minutes)

Permeability Meter The permeability meter comprises of a cylinder and another concentric cylinder inside the outer cylinder and the space between the two concentric cylinders is filled with water. A bell having a diameter larger than that of the inner cylinder but smaller than that of outer cylinder, rests on the surface of water. Standard sand specimen of 5.08 mm diameter and 50.8 mm height together with ram tube is placed on the tapered nose piece of the permeability meter. The bell is allowed to sink under its own weight by the help of multi-position cock. In this way the air of the bell streams through the nozzle of nosepiece and the permeability is directly measured.

Procedure:

2000 cc of water held in the inverted bell jar is allowed to pass through the sand specimen.
A situation comes when the liquid entering the specimen equals the air escaped through the specimen.
This gives a stabilized pressure reading on the manometer and the same can be read on the vertical scale.
Simultaneously, using as stop watch the time required for 2000cc of water to pass through the sand of specimen is also recorded.