## How to Calculate and Solve for Permeability Number | Refractories

The permeability number is illustrated by the image below. To compute for the permeability number, five essential parameters are needed and these parameters are Volume of Air (V), Height of the Specimen (H), Cross-sectional Area (A), Air Pressure (P) and Time (t).

The formula for calculating permeability number:

PN = VH/APt

Where:

PN = Permeability Number
V = Volume of Air
H = Height of the Specimen
A = Cross-sectional Area
P = Air Pressure
t = Time

Let’s solve an example;
Find the permeability number when the volume of air is 2, the height of the specimen is 7, the cross-sectional area is 3, the air pressure is 9 and the time is 4.

This implies that;

V = Volume of Air = 2
H = Height of the Specimen = 7
A = Cross-sectional Area = 3
P = Air Pressure = 9
t = Time = 4

PN = VH/APt
PN = (2)(7)/(3)(9)(4)
PN = (14)/(108)
PN = 0.129

Therefore, the permeability number is 0.129.

## How to Calculate and Solve for Standard Permeability of Sand | Solidification of Metals The image above represents standard permeability of sand.

To compute for standard permeability of sand, five essential parameters are needed and these parameters are Volume of Area (V), Height of Sand Specimen (H), Pressure (Pr), Cross-Sectional Area of Sand Specimen (A) and Time (t).

The formula for calculating the standard permeability of sand:

P = VH / PrAt

Where:

P = Standard Permeability of Sand
V = Volume of Air
H = Height of Sand Specimen
Pr = Pressure
A = Cross-Sectional Area of Sand Specimen
t = Time

Let’s solve an example;
Find the standard permeability of sand when the volume of air is 6, the height of sand specimen is 3, the pressure is 8, the cross-sectional area of sand specimen is 5 and the time is 2.

This implies that;

V = Volume of Air = 6
H = Height of Sand Specimen = 3
Pr = Pressure = 8
A = Cross-Sectional Area of Sand Specimen = 5
t = Time = 2

P = VH / PrAt
P = 6 x 3 / 8 x 5 x 2
P = 18 / 80
P = 0.225

Therefore, the standard permeability of sand is 0.225.

Calculating the Volume of Air when the Standard Permeability of Sand, the Height of Sand Specimen, the Pressure, the Cross-Sectional Area of Sand Specimen and the Time is Given.

V = P x PrAt / H

Where:

V = Volume of Air
P = Standard Permeability of Sand
H = Height of Sand Specimen
Pr = Pressure
A = Cross-Sectional Area of Sand Specimen
t = Time

Let’s solve an example;
Find the volume of air when the standard permeability of sand is 10, the height of sand specimen is 2, the pressure is 4, the cross-sectional area of sand specimen is 8 and the time is 1.

This implies that;

P = Standard Permeability of Sand = 10
H = Height of Sand Specimen = 2
Pr = Pressure = 4
A = Cross-Sectional Area of Sand Specimen = 8
t = Time = 1

V = P x PrAt / H
V = 10 x (4)(8)(1) / 2
V = 320 / 2
V = 160

Therefore, the volume of air is 160.