It is therefore wrong to apply to
acetylene gasholders formulae in which a correction for the lifting power
of the gas has been included when such correction is based on the average
specific gravity of coal-gas, as is the case with many abbreviated
gasholder pressure formulae.
The correction for the immersion of the sides of the bell is of greater
magnitude, and has an important practical significance. Let H be the
total height in inches of the side of the gasholder, _h_ the height
in inches of the top of the sides of the gasholder above the water-level,
and _w_ = the weight of the sides of the gasholder in lb.; then, for
any position of the bell, the proportion of the total height of the sides
immersed (H - _h_)/H, and the buoyancy is (H - _h_)/H x
_w_/S + pi/4_d^2_, in which S = the specific gravity of the
material of which the bell is made. Assuming the material to be mild
steel or wrought iron, having a specific gravity of 7.78, the buoyancy is
(4_w_(H - _h_)) / (7.78Hpi_d^2_) lb. per square inch
(_d_ being inches and _w_ lb.), which is equivalent to
(4_w_(H - _h_)) / (0.03604 x 7.78Hpi_d^2_) =
(4.54_w_(H - _h_)) / (H_d^2_) inches of water. Hence the
complete formula for acetylene gasholders is:
_p_ = 35.
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