Fig. 37. Ellison Draft Gauge
The gauge is first leveled by means of the small level attached to it, both legs being open to the atmosphere. The liquid is then adjusted until its meniscus rests at the zero point on the left. The right-hand leg is then connected to the source of draft by means of a piece of rubber tubing. Under these circumstances, a rise of level of one inch in the right-hand vertical tube causes the meniscus in the inclined tube to pass from the point 0 to 1.0. The scale is divided into tenths of an inch, and the sub-divisions are hundredths of an inch.
Fig. 38. Peabody
Draft Gauge
The makers furnish a non-drying oil for the liquid, usually a 300 degrees test refined petroleum.
A very convenient form of the ordinary U-tube gauge is known as the Peabody gauge, and it is shown in Fig. 38. This is a small modified U-tube with a sliding scale between the two legs of the U and with connections such that either a draft suction or a draft pressure may be taken. The tops of the sliding pieces extending across the tubes are placed at the bottom of the meniscus and accurate readings in hundredths of an inch are obtained by a vernier.
FOOTNOTES
[52] Results secured by this method will be approximately correct.
[53] See “Chimneys for Crude Oil”, C. R. Weymouth, Trans. A. S. M. E., Dec. 1912.