Instrumentation and SCADA · Level, Pressure, and Temperature
What Is Differential Pressure?
Differential pressure is the difference between two pressure points.
It can show resistance across a screen, filter, or other equipment. When differential pressure is used to measure flow across an orifice or venturi, flow changes with the square root of the pressure difference, so doubling the flow makes the pressure difference about 4 times larger. Tubing or sensing lines must be open and correctly connected. A plugged line can create a false difference.
The indicated pressure difference stays high after a filter is cleaned. A technician finds one sensing line blocked with solids.
The high and low sides must be connected to the correct locations. Reversing them can produce a negative or backward result. Equalizing valves may be used during service, but leaving one open can hide the true difference. Operators should know the normal valve lineup without changing it casually. When the reading disagrees with process condition, inspect for closed valves, leaks, air, frozen lines, or solids. Qualified staff should handle adjustments and tubing work.
Check sensing valves and lines before deciding the process restriction is real.
Key point: Differential pressure is the difference between two pressure points. A plugged sensing line can create a false difference.
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Wastewater Instrumentation, SCADA, and Process Control Fundamentals
This page comes from the course. It covers plant instruments, signals and control, flow, level, pressure and water-quality measurement, SCADA and alarms, and instrument maintenance, one step at a time, with short knowledge checks and a certificate of completion.
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