Differential Pressure

Differential pressure usually refers to fluid force per unit, measured in pounds per square inch (PSI) or alternative measurement unit subtracted from a higher level of force per unit. This calculation is often taken for pressures inside and outside a pipe or at specific points along a flow path. This calculation has applications across multiple industries and applications.

Measuring differential pressure along a line helps identify blockage points whilst monitoring pressure at various points along a fluid line is vital for operational safety.

A differential pressure gauge is often used in a process system to measure and display the difference in pressure between two pressure points. They usually have two inlets, each connected to the pressure points that require monitoring. The differential pressure gauge performs the mathematical operation of subtraction through mechanical or electronic means. Thus removing the need for an operator or control system to monitor two separate gauges and determine the differences manually.

Differential Pressure in Filtration

Good filtration is essential for the efficient operation of industrial process systems. By monitoring differential pressures, contaminated or clogged filters can be detected and identified. As a filter becomes clogged with foreign materials, the pressure before the filter increases. Using a differential pressure gauge, it is possible to measure the pressure before and after the filter. The more the differential pressure increases the more the likely the filter is blocked. The filter can changed once the differential pressure reaches a set value.

Differential Pressure in Liquid Level Monitoring

An atmospheric pressure gas blanket is often used on top of liquids in sealed tanks. Since the pressure of the gas blanket adds to the hydrostatic pressure it can be difficult to get an accurate level measurement using a conventional pressure gauge. Differential pressure gauges measure the difference in gas pressure from the total pressure, thus translating into a true liquid level reading. A differential pressure gauge can also be used on production and injection wells to measure the difference between reservoir pressure and bottom-hole pressure, or between injection pressure and average reservoir pressure.

Differential Pressure in Flow Monitoring

Differential pressure gauges are often used to measure the flow of a liquid inside a pipe. The differential pressure gauge measures the pressure before and after a reduction in the pipework. The pressure drop is then mechanically or electronically converted by the differential pressure gauge into the flow rate.

Differential pressure gauges are an uncomplicated solution for a visual indicator when measuring process flow. Alternatively, pressure sensors can be combined within a monitoring system to monitor and log differential pressures. HVAC professionals often use handheld differential pressure instruments to perform maintenance and inspection tasks.