But as the increase is greater the
lower the density of the gas, the disturbing influence of a moderate rise
in a pipe is comparatively small in the case of a gas of so high a
density as acetylene. Hence in most instances it will be unnecessary to
make any allowance for increase of pressure due to change of level. Where
the change is very great, however, allowance may advisedly be made on the
following basis: The pressure of acetylene in pipes increases by about
one-tenth of an inch (head of water) for every 75 feet rise in the pipe.
Hence where acetylene is supplied from a gasholder on the ground-level to
all floors of a house 75 feet high, a burner at the top of the house will
ordinarily receive its supply at a pressure greater by one-tenth of an
inch than a burner in the basement. Such a difference, with the
relatively high pressures used in acetylene supplies, is of no practical
moment. In the case of an acetylene-supply from a central station to
different parts of a mountainous district, the variations of pressure
with level should be remembered.
The distributing formulae also assume that the pipe is virtually straight;
bends and angles introduce disturbing influences.
Pages:
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470