Disturbance Factor (Steam Blowing) Calculator

Choose disturbance factor, density, or speed to solve, then enter the displayed values. Use local conditions at the same pipe section; the ratio alone does not establish cleaning acceptance.

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Disturbance Factor (Steam Blowing) Formula

The disturbance factor compares the dynamic pressure during steam blowing to the dynamic pressure at maximum continuous rating, usually called MCR. The calculator uses density and velocity at both conditions.

DF = (0.5 \times rho b \times V b ²) / (0.5 \times rhoₘ \times Vₘ²)

The 0.5 terms cancel, so the same formula can also be written as:

DF = (rho b \times V b ²) / (rhoₘ \times Vₘ²)

Rearranged formulas for solving a missing input:

rho b = (DF \times rhoₘ \times Vₘ²) / (V b ²)

V b = sqrt((DF \times rhoₘ \times Vₘ²) / rho b)

rhoₘ = (rho b \times V b ²) / (DF \times Vₘ²)

Vₘ = sqrt((rho b \times V b ²) / (DF \times rhoₘ))

DF = disturbance factor, unitless
rho_b = density at blow condition
V_b = velocity at blow condition
rho_m = density at MCR condition
V_m = velocity at MCR condition

The density inputs may be entered in kg/m³, g/cm³, or lb/ft³. The velocity inputs may be entered in m/s, km/h, or ft/s. The calculator converts these values to base units before applying the formula.

Select the value to solve. For disturbance factor, enter all four densities and speeds. For an inverse calculation, enter the factor and three displayed conditions. Positive densities and speeds are required.

Common Unit Conversions for Steam Blowing Calculations

Use these conversions when checking values by hand or comparing data from different sources.

Quantity	Unit	Conversion to base unit
Density	kg/m³	1 kg/m³
Density	g/cm³	1 g/cm³ = 1000 kg/m³
Density	lb/ft³	1 lb/ft³ ≈ 16.01846337 kg/m³
Velocity	m/s	1 m/s
Velocity	km/h	1 km/h = (1/3.6) m/s ≈ 0.277778 m/s
Velocity	ft/s	1 ft/s = 0.3048 m/s

Disturbance Factor Result Guide

Disturbance factor	Meaning
Less than 1.0	The blow condition has lower dynamic effect than the MCR condition.
Equal to 1.0	The blow condition and MCR condition have the same dynamic pressure basis.
Greater than 1.0	The blow condition has a higher dynamic-pressure basis; this alone does not prove cleaning acceptance.

Example

Example 1: Calculate disturbance factor

Suppose the density at blow condition is 4 kg/m³, the velocity at blow condition is 220 m/s, the density at MCR is 5 kg/m³, and the velocity at MCR is 160 m/s.

DF = (4 \times 220²) / (5 \times 160²)

DF = 193600 / 128000 = 1.5125

The disturbance factor is 1.5125.

Example 2: Calculate velocity at blow condition

Suppose the disturbance factor is 1.5, the density at blow condition is 4 kg/m³, the density at MCR is 5 kg/m³, and the velocity at MCR is 160 m/s.

V b = sqrt((1.5 \times 5 \times 160²) / 4)

V b = sqrt(48000) \approx 219.0890 m / s

The velocity at blow condition is 219.0890 m/s.

FAQ

What does disturbance factor mean in steam blowing?

Disturbance factor is a ratio of dynamic pressure at the steam blowing condition to dynamic pressure at the MCR condition. A higher value means a higher local dynamic-pressure basis relative to rated operation. Cleaning acceptance also depends on the approved procedure, geometry, duration, target inspection, and equipment limits.

Why is velocity squared in the disturbance factor formula?

Dynamic pressure is proportional to density times velocity squared. Because velocity is squared, a small increase in velocity can cause a much larger increase in disturbance factor.

Does disturbance factor have a unit?

No. Disturbance factor is unitless because it is a ratio of two dynamic pressure terms. The density and velocity units still matter during calculation, so values must be converted consistently before applying the formula.

Disturbance Factor (Steam Blowing) Calculator screenshot