This section is from the book "The Tinman's Manual And Builder's And Mechanic's Handbook", by Isaac Ridler Butt. Also available from Amazon: The Tinman's Manual And Builder's And Mechanic's Handbook.

The best Velocity of Circumference for different Densities.

Velocity of Circumference. Feet per Second. | Density of Blast. Oz. per inch. |

170 | 3 |

180 | 4 |

195 | 5 |

205 | 6 |

215 | 7 |

A speed of 180 to 200 feet per second, giving a density of 4 or 5 oz., is very suitable for smithy fires.

250 to 300 feet per second is a proper speed for cupolas.

A fan 4 feet 0 inch diameter, blade 1 foot 0 inch square, will supply 40 fires with 1 5/8 tuyeres at a density of 4 oz.

To find the Horse Power required for any fan,

Let D = density of blast in oz. per inch.

A = area of discharge at tuyeres in square inches. V = velocity of circumference in feet per second.

Then V2 / 1000 X D X A / 963 = Effective Horse Power required.

To find the density to be attained with any given fan. Let D = diameter of fan in feet.

Then (V/4)2 / 120 X d. = Density of blast in oz. per inch. Or the density may be found by comparison with the following table: -

Velocity of Circumference. Feet per Second. | Area of Nozzles. | Density of Blast. Oz. per inch. | |

150 | Twice area of blades | 1 | |

150 | Equal | ditto | 2 |

150 | 1-2 | ditto | 3 |

170 | 1-4 | ditto | 4 |

200 | 1-2 | ditto | 4 |

200 | 1-6 | ditto | 6 |

220 | 1-3 | ditto | 6 |

To find the quantity of air that will be delivered by any Fan, the density being known.

Total area nozzles, sq. ft. X velocity, ft. per minute corresponding to density (as per table) = Air delivered, cubic ft. per minute.

Density. Oz. per Sq. Inch. | Velocity. Feet per Minute. |

1 | 5,000 |

2 | 7,000 |

3 | 8,600 |

4 | 10,000 |

5 | 11,000 |

6 | 12,250 |

7 | 13,200 |

8 | 14,150 |

9 | 15,000 |

10 | 15 800 |

11 | 16,500 |

12 | 17,300 |

Density. Lbs. per Sq. Inch | Velocity. Feet per Minute. |

1 | 20,000 |

1½ | 24,500 |

2 | 28,300 |

2½ | 31,600 |

3 | 44,640 |

4 | 40,000 |

6 | 49,000 |

8 | 56.600 |

10 | 63,200 |

12 | 69,280 |

15 | 78,000 |

20 | 89,400 |

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