Steam Pipes - Sizing
Sizing of steam pipe lines - major and minor loss in steam distribution systems.
The pressure available for distribution of steam is the pressure difference between the initial pressure at the boiler, and the required final pressure at the end of the line - at the steam consumer.
The pressure difference available for the distribution system can be expressed as:
p = pj - pk (1)
where
p = available pressure drop (Pa (N/m2), psi (lb/ft2))
pj = initial or boiler pressure (Pa (N/m2), psi (lb/ft2))
pk = final pressure (Pa (N/m2), psi (lb/ft2))
The total pressure drop in the distribution system is a result of friction (major loss) and pressure loss in fittings (minor loss), and can be expressed as:
pt = pmajor + pminor (2)
where
pt = total pressure drop in the system (Pa (N/m2), psi (lb/ft2))
pmajor = pressure loss in pipes due to friction (Pa (N/m2), psi (lb/ft2))
pminor = pressure loss in fittings (Pa (N/m2), psi (lb/ft2))
Friction - Major Loss
Major loss - the pressure loss due to friction in a low pressure steam distribution system can be expressed as:
pmajor = pa l (3)
where
pa = pipe friction resistance per unit length of pipe (Pa/m (N/m2/m), psi/ft (lb/ft2/ft))
l = length of pipe (ft, m)
The pressure drop in a steam pipe can be expressed as
pa-100 = 0.01306 q2 (1 + 3.6/di) / (3600ρ di5) (3b)
where
pa-100 = pressure drop per 100 ft pipe (psig / 100 ft)
q = steam flow rate (lb/h)
di = inside diameter of pipe (in)
ρ = density of steam (lb/ft3)
Loss due to Fittings - Minor loss
Loss due to fittings - minor loss can be expressed as:
pminor = ξ 1/2ρ v2 (4)
where
ξ = minor loss coefficient
pminor = pressure loss (Pa (N/m2), psi (lb/ft2))
ρ = density (kg/m3, slugs/ft3)
v = flow velocity (m/s, ft/s)
Equivalent length
Minor loss - loss due to fittings can also be expressed as equivalent length:
pminor = pa le (5)
or
pt = pa(l + le) (6)
where
le = equivalent length of the fittings (ft, m)
As a rule of thumb the total pressure drop is about 5 -10% of initial pressure per 100 m pipe.
Typical Steam Velocities
- Exhaust steam - 20 to 30 m/s (70 - 100 ft/s)
- Saturated steam - 30 to 40 m/s (100 - 130 ft/s)
- Superheated steam - 40 to 60 m/s (130 -200 ft/s)
Related Topics
-
Sizing of Steam and Condensate Pipes
Dimensions of steam and condensate pipe lines. Calculate pressure losses, recommended velocities, capacities and more. -
Steam and Condensate
Design of steam & condensate systems with properties, capacities, sizing of pipe lines, system configuration and more.
Related Documents
-
ANSI Schedule 40 Steel Pipes - Dimensions
Internal and external diameters, areas, weights, volumes and number of threads for ANSI schedule 40 steel pipes. -
Condensate Pipe Lines - Sizing
Flow and pressure loss in condensate return lines - SI Units. -
Horizontal Pipe Hanger Supports - Spacing and Rod Size
Recommended maximum support span between hangers - and rod sizes for straight horizontal pipes. -
Insulated Steam Pipes - Condensate Generated (kg/h per 100m)
Heat loss from steam pipes generates condensate which must be drained from the system. -
Recommended Velocities in Steam Systems
The steam velocity in a steam distribution system should be within certain limits to avoid excessive wear and tear -
Sizing Steam Pipes (kg/h)
Steam is a compressible gas where pipe line mass flow capacity depends on steam pressure. -
Sizing Steam Pipes (lb/h)
Steam is a compressible gas where the capacity of a pipe line depends on the size of the pipe and the steam pressure. -
Steam Flow Rate vs. Pressure Drop - Schedule 40 Pipe
Flow rate (lb/h) and pressure drop per 100 feet of pipe. -
Steam Heating Processes - Load Calculating
Calculating the amount of steam in non-flow batch and continuous flow heating processes. -
Steam Heating Systems - Design
An introduction to the basic design of steam heating systems. -
Steam Pipes - Installation of Drip Legs
Properly draining steam pipes for condensate. -
Steam Pipes - Online Pressure drop Calculator
Calculate pressure drops in steam distribution pipe lines. -
Steam Pipes - Pressure Drop vs. Steam Flow
Steam pipes and pressure drop diagrams - imperial and metric units. -
Steam Trap Selection Guide
Steam trap selection guide - Float & Thermostatic, Inverted Bucket, Bimetal Thermostatic, Impulse and Thermodynamic Disc steam traps. -
Steel Pipes - Thermal Expansion Loops
Calculating and sizing steel pipe thermal expansion loops. -
Thermal Expansion of Steam Pipes - (inches)
Expansion of steam pipes heated from room temperature to operation temperature.
