static pressure

Static pressure (often written as Ps) is the pressure the fan must develop to overcome resistance in a ventilation system. In mining, static pressure is the “cost” you pay to move airflow through airways, regulators, and especially through ducting to a heading. That’s why fan/blower selection should be based on the duty point Q@Ps, not on a free-air airflow figure measured near 0 Pa.

Static pressure demand increases when system resistance increases. In a ducted heading, resistance grows with:

• Duct length: friction loss accumulates as headings advance.
• Bends, reducers, and fittings: localized losses can be large, especially with sharp bends.
• Duct condition and leakage: leaks waste airflow and can require higher fan pressure to achieve the same end-of-duct delivery.

In practical terms, a unit that produces excellent airflow at low static pressure may deliver disappointing airflow at the face once the duct system demands higher pressure. This is the common “rating trap” underground: nameplate airflow looks strong, but real end-of-duct airflow falls short because the system operates at a much higher Ps than assumed.

When specifying static pressure for a mining application, be clear about:

• Where the duty point applies (mine network, district circuit, or end of duct).
• Units: Pa is common internationally; in.w.g. is often used in some markets.
• Operating range: mines change—design for expected resistance growth and realistic duct conditions.

Static pressure also connects directly to motor sizing and energy use. Higher Ps at a given airflow typically means higher required power, so confirm motor kW margin and consider air-density effects at high altitude or high temperature. For many mines, adding a VFD improves control by allowing speed adjustments to maintain target airflow as Ps requirements shift.

Bottom line: in mining ventilation, static pressure is not a technical detail—it is the key variable that decides whether air actually reaches the working face.