Other viscosimeters in use are the Engler, Tagliabue, Scott, Redwood, Penn. Ry. pipet, McMichael, Lamansky-Nobel, Ost wald, Martens, Stormer, Ubbelohde, Lepenau, Kuenkler, Albrecht, Arvine, Barbey, Cockrell, Doolittle, Gibbs, Mason, Napier, Nas myth, Phillips, Reischauer, Magruder. The Engler viscosimeter ( See fig. 5) is used most extensively in Germany and its dimen sions are as follows : Inside diameter of the inside vessel for oil. .. 106 mm.
Height of vessel below overflow 25 mm.
Length of the oil jet 20 mm.
Inside diameter of the oil jet upper end 2.9 mm.
Inside diameter of the oil jet lower end 2 8 mm.
Length of jet projecting from lower part of outer vessel 3 0 mm.
\Vidth of jet 4 5 mm.
The quotient of the time of outflow of 200 c.c. of oil divided by the time of outflow of 200 c.c. of water is taken as a measure of the viscosity or is the so-called Engler degree. The RedwoOd viscosimeter is used extensively in England.
Table 6 gives equivalents of Saybolt times, Redwood times, and Engler numbers.a Intermediate values can be obtained by interpolation. Fig. 6 is a charts for the quick determination of these equivalents.
Knowledge of the viscosity of fuel oil is valuable for de termining the ease with which the oil can be pumped through pipe lines with or without heat. Although the viscosity of fuel
oil increases with the• density, tests have shown that oils of the same specific gravity from different localities often differ quite widely in viscosity.
Fuel oil, as regards viscosity, may be divided into two general classes, namely : Class 1. Asphaltic base crudes, residuums, or other oils which require heating facilities to reduce the viscosity in order that the oil may be handled by the storage and burning equipment. Class 2. Oils of a sufficiently low viscosity to make heating equipment unnecessary. In general, an oil in Class 1 should not have a viscosity above 2,000° Engler'at 60° F. Oils of a higher viscosity than this can be used at plants provided with special equipment. It is imperative that oils of this class be heated to a temperature at which they have a viscosity of 12° Engler or lower before they reach the burner, in order to obtain proper atomization. It is desirable that this viscosity be obtained at a temperature below the flash point of the oil, in order to minimize fire hazards and to insure uniform feed to the burner. For an oil of Class 2, 12° Engler at 60° F. is the approximate maximum viscosity permissible.