D. S. DAVIS
ORIFICE NOMOGRAPH
IF-ayne Universitl-, Detroit, Micli.
'X'
100
Key
C-A-h A-R-d 8D
-60
40
i
0'2
0.10
0 08
0.06
F
REQUEn'TLYgit is necessary to calculate the rate of flow of water through standard orifices, nozzles, and spray pipes. The discharge expression,
orifice in a plate of thickness equal to from 2 to 3 orifice diameters'. ,4s an illustration of the use of the chart : K h a t is the rate of flow, in gallons of water per minute, through a '/(-inch hole in a wall "/e inch thick under a head of 30 feet of water? The thickness of the wall is 2.5 times the diameter of the hole, corresponding to a coefficient of 0.82. Following the key and the broken lines on the chart, connect 0.82 on the C scale with 30 on the h scale and note the intersection with the A axis. Connect this intersection xvith inch on the d scale and read the rate of flow on the R scale as 5.52 gallons per minute. Conversely, what head is needed t o ensure a rate of flow of 20 gallons of water per minute through a standard beveled orifice in a thin plate? Connect 11%inch on the d scale with 20 on the R scale and note the intersection with the A axis. Connect 0.61, the gage point for a standard orifice, with thib intersection and produce the line to meet the h scale a t 44.8, the required head in feet. Index lines for this solution are not s1iov-n on the chart.
Q = CAT' where Q = rate of flow, cu. ft./sec. C = orifice constant, dependent upon design A = area of orifice, sq. it. P V = velocity of flow, ft./sec.
can be w i t t e n Q = C A d T h = 8.02CAdX
4%
by substituting for i', where h is the head of water in feet. To avoid small numerical values, the rate of flow in gallons perLminute is more convenient and is given by R where!d'=
= 19.64Cdal/J;
diameter of orifice, in.
1
The alignment chart solves the expression readily and bears several gage points corresponding to values of C for four commonly used types of orifice: the short or free-running Borda mouthpiece, square and beveled orifices in thin plates, and an
1 Perry's Chemical Engineers' Handbook, pp. 607, 702, 703, Kew P o l k , i\IoGrau~-IIillBook Co , 1934.
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