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f                                            24          APPLICATION OF THE  LAWS OF  HYDRAULICS



construction in which the gas flows directly from the producer

I                                      into the underground conduit or gas flue will always possess latent

v      '                               possibilities of an explosion, because the gas in the producer will

*                               be at such a low pressure that there will be a negative pressure in

the underground flue,  with producers working without forced

A gas producer with mains connected in this manner was
installed at the Alapayevsky works.    The producer was worked
without forced draft and the gas main was long.    When placed in
!|                                operation this proved so dangerous that it became necessary to

replace the gas main with a metal main forming a Siemens siphon.
When this was done there were no more explosions.

4. This method of computing hydrostatic pressure may be

t                                 applied to the gas mains of a blast furnace producing charcoal iron.

These furnaces have very large bells for charging and the volume
of gas is relatively small.    The percentage of the gas lost by the

!                                 bells is considerable and increases rapidly as the pressure of the gas

i ;,                               in the mains increases.    For this reason it is very important that

I"'                                   the mains should be designed to require the minimum of gas pressure

j                                     to overcome the unavoidable resistance to the flow of the gas.

I /                                   It is also possible to determine the excess of pressure required to

;'                                   overcome the resistance created by poorly designed gas main, too

j|                                   small for the volume of gas flowing, having sharp bends, etc.

!''!                                             Assuming that the height of the furnace is 20 m, the height of a

I                                cubic meter of the gas being 1 kg 22 and the temperature in the

!                                 main 200, the hydrostatic pressure required at the top of the

|'i                                furnace can be determined.    Assuming, on the other hand, that

I f                                       the gas is to be burned under boilers located 3 meters below the

!                                hearth level of the blast furnace, the pressure in the gas mains

]                                or the burners at the boiler after regulation and control, must not

1                                be less than the atmospheric pressure.

The gas mains form an enclosure or chamber 23 meters in
height, filled with a' light gas which has the following weight per
cubic meter:

1 22

The hydrostatic pressure will be, therefore,
3 = 23 (1 .29 - 0.705) = 13 kg 45 per square meter,