Brookfield BF35 Manual do Utilizador descarregar pdf (Página 10)

Brookeld Engineering Labs., Inc. Page 10 Manual No. M13-10000

Shear Stress Conversions

To convert from units on left side to units on top, multiply by factor @ intercept

Dyne/cm

Pa lb/100ft

lb/ft

Dyne/cm

1 0.1 0.2084 0.002084 0.1957

Pa 10 1 2.084 0.02084 1.957

lb/100ft

4.788 0.4788 1 0.01 0.939

lb/ft

478.8 47.88 100 1 93.9

DR 5.107 0.5107 1.065 0.01065 1

What Bob and Spring Should I Use?

There is often confusion or misunderstanding about what a viscometer can actually measure. For

example, a viscometer with an R1B1 F1 combination can measure water fairly well at 100 RPM

and higher, but at 3 RPM, the readings would be shaky at best. While on the other hand, a linear

uid with a viscosity of 15000, could not get past 6 RPM with the same combination.

To estimate which spring might be best, use the formula below to calculate a Minimum Spring

factor, where one establishes the maximum RPM the uid is going to be tested at, as well as what

the expected “Apparent Viscosity” of the uid at that RPM. If the Factor comes out as .87, then an

F 1.0 spring should be used. If it comes out as .16, then an F 0.2 spring would be best. To cover all

ranges, it may be necessary to use more than one spring.

Minimum Spring Factor (F) =

RPM(max) * AV(max)

BOB(F)*90000

Bob (F)

R1B1 1

R1B2 8.9

R1B3 25.4

R1B4 50.7

1 2 ... 5 6 7 8 9 10 11 12 13 14 15 ... 22 23

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Brookfield BF35 Manual do Utilizador Página 10