CONDENSERS 193
The temperature of the overflow from air pump to hot well should not be over 100° F. Water will be lifted I foot for each inch of vacuun.
VACUUM GAUGE.
Ilow is vacuum recorded?
The vacuum is recorded by a vacuum gauge connected with the condenser and piped to the engine-room. It reg- isters the vacuum in inches. Inches are used instead of pounds, because they correspond with the mercury column, the mercury column being always used to measure the press- ure of the atmosphere. A mercury column is frequently used in place of a vacuum gauge. With a perfect vacuum a column of mercury 30 inches high will be supported by the atmosphere. Vacuum gauges are usually graduated to agree with the scale of the barometer, and the vacuum is usually stated in inches of mercury. The absolute pressure of steam is measured from zero, and consists of the pressure indicated by the steam gauge (which is known as pressure above atmosphere).
