FMC Corporation - Talstar 80 - Handbuch (Seite 101)

Proline Promass 80 PROFIBUS PA Technical data
101
Limiting flow See the "Measuring range" section
→ Page 88 ff.
Select nominal diameter by optimizing between required flow range and permissible pressure loss.
See the "Measuring range" section for a list of max. possible full scale values.
• The minimum recommended full scale value is approx. 1/20 of the max. full scale value.
• In most applications, 20 to 50% of the maximum full scale value can be considered ideal.
• Select a lower full scale value for abrasive substances such as liquids with entrained solids (flow
velocity < 1 m/s (3 ft/s)).
• For gas measurement the following rules apply:
– Flow velocity in the measuring tubes should not be more than half the sonic velocity
(0.5 Mach).
– The maximum mass flow depends on the density of the gas: formula
→ Page 91
Pressure loss (SI units) Pressure loss depends on the properties of the fluid and on its flow. The following formulas can be
used to approximately calculate the pressure loss:
Pressure loss formulas for Promass F, M, E
Pressure loss formulas for Promass H, I, S, P
Reynolds number
a0004623
Re
≥ 2300 *
a0004626
Re < 2300
a0004628
Δp = pressure loss [mbar]
ν = kinematic viscosity [m2/s]
g = mass flow [kg/s] ρ = fluid density [kg/m3]
d = inside diameter of measuring tubes [m]
K to K2 = constants (depending on nominal diameter)
* To compute the pressure loss for gases, always use the formula for Re ≥ 2300.
Reynolds number
a0003381
Re ≥ 2300 *
a0004631
Re < 2300
a0004633
Δp = pressure loss [mbar]
ν = kinematic viscosity [m2/s]
g = mass flow [kg/s] ρ = fluid density [kg/m3]
d = inside diameter of measuring tubes [m]
K to K3 = constants (depending on nominal diameter)
* To compute the pressure loss for gases, always use the formula for Re
≥ 2300.
Re =
2 · g
p n r · d · ·
D r p = K · · · 0.25 1.85 –0.86 g n
Dp = K1 · · + g n
K2 · · 0.25 2 g n
r
Re = p
n r · d · ·
4 · g
D n r p = K · · · 0.25 1.75 –0.75 g
K3 · g 2
r +
Dp = K1 · · g n K3 · g 2
r +