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Valve Materials and Elastomers

Posted in: Engineering guides

06/14/2026

Valve material selection should not be based only on nominal pressure or valve size. Operating pressure, temperature,...

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Pressure Drop in Steam Lines

TECHNICAL DATA

Technical Reference for Steam Piping Systems

Pressure drop in a steam distribution network directly affects the available pressure at the point of use, as well as the operation of control valves, pressure reducing valves, steam traps and heat exchangers.

For preliminary technical checks, pressure drop may be estimated using the steam density, flow velocity and the total resistance coefficient of the pipework and installed components.

Basic Calculation Formula

Δp = C × ρ × w² / 2

Δp: pressure drop
C: flow resistance coefficient of the pipe or component
ρ: steam density, in kg/m³
w: steam velocity, in m/s

In practice, the total resistance coefficient is calculated by adding the individual resistance coefficients of the pipework and fittings:

C_total = C_pipe + C_valves + C_elbows + C_tees + C_fittings

Typical Factors Increasing Pressure Drop

Pipeline Component	Effect on Pressure Drop	Engineering Note
Long pipe runs	Increased friction losses	The effect increases as steam velocity increases.
Angle valves	Medium to high resistance	The change in flow direction creates additional pressure losses.
Globe valves	Higher resistance than full-bore isolation valves	Suitable for control duties, but with higher local pressure drop.
Fully open gate valves	Low resistance	Mainly used for isolation, not for regulation.
90° elbows	Local pressure loss	Multiple elbows in short pipe runs can significantly increase losses.
Tee pieces	Local resistance due to branching or change of direction	The loss depends on flow direction and tee configuration.
Special valves and fittings	Variable resistance	Manufacturer technical data should be checked.

Pressure Drop Calculation Example

For a DN 50 steam line including a pipe run, valves, a tee piece and elbows, the total resistance coefficient is calculated by adding the individual resistance values.

Component	Quantity / Data	Coefficient C
DN 50 pipeline	Length 20 m	8.1
Angle valve	1 piece	3.3
Special valves	2 pieces	5.6
Tee piece	1 piece	3.1
90° elbows	2 pieces	1.0
Total	ΣC	21.1

Operating Data

Steam temperature: 300°C
Absolute steam pressure: 16 bar
Steam velocity: 40 m/s

Indicative result: Δp ≈ 1.1 bar

Engineering Notes

Pressure drop should be considered when sizing steam lines, especially where control valves, pressure reducing valves, strainers, separators, steam traps and multiple changes of direction are installed.

Excessive pressure drop may result in insufficient pressure at the point of use, reduced heat transfer performance, unstable control and increased flow velocity. High steam velocities may also increase noise, erosion, energy losses and the risk of water hammer.

Final equipment selection should consider operating pressure, temperature, flow rate, steam density, steam quality, pipe losses and the technical characteristics of each valve or component.

Related Equipment for Steam Systems

Philippopoulos S.A. supplies equipment for industrial and marine steam systems, including isolation valves, control valves, pressure reducing valves, safety valves, steam traps, strainers, separators, condensate pumps and boiler house equipment.