Understanding Pressure Loss in Piping Systems: Causes, Effects, and Engineering Considerations

1. What Causes Pressure Loss?

Pressure loss in a piping system is primarily caused by two mechanisms:

a) Frictional Losses (Major Losses)

These occur due to the friction between the fluid and the internal wall of the pipe, as well as the internal friction within the fluid (viscosity). Factors affecting frictional losses include:

• Pipe length (longer pipe → higher loss)

• Pipe diameter (smaller diameter → higher velocity → higher loss)

• Fluid velocity

• Surface roughness of the pipe

• Fluid viscosity and density

Darcy-Weisbach Formula:

$$h_f = f \cdot \frac{L}{D} \cdot \frac{v^2}{2g}$$

Where:

• $h_f$: head loss due to friction (m)

• $f$: Darcy friction factor

• $L$: pipe length (m)

• $D$: pipe diameter (m)

• $v$: fluid velocity (m/s)

• $g$: gravitational acceleration (9.81 m/s²)

b) Local or Minor Losses

These result from flow disturbances caused by pipe fittings, bends, valves, expansions, contractions, or any sudden changes in direction or flow area. These cause turbulence and energy dissipation.

Minor Loss Formula:

$$h_l = K \cdot \frac{v^2}{2g}$$

Where:

• $h_l$: local head loss

• $K$: loss coefficient (varies with component type)