Level Measurement
DP level measurement, seal pots, zero suppression/elevation, ultrasonic, radar, GWR, capacitance, and bubbler systems.
- Explain differential pressure level measurement principles
- Define zero suppression and zero elevation and when each is required
- Compare ultrasonic, radar, and guided wave radar level technologies
- Describe capacitance and bubbler level measurement systems
Leçon 1
Differential Pressure Level Measurement
DP Level Principle
Differential pressure (DP) level measurement is the most widely used method for measuring liquid level in process vessels. The principle is straightforward: the hydrostatic pressure at the bottom of a liquid column is proportional to the height of the liquid. By measuring this pressure with a DP transmitter, the level can be inferred.
The formula is: Pressure = Density x Gravity x Height
The DP transmitter measures the difference between the pressure at the bottom of the vessel (high side) and the pressure above the liquid (low side, which accounts for gas or vapor pressure).
Seal Pots
A seal pot is a small reservoir installed on the low-pressure side of a DP level measurement on a closed (pressurized) vessel. Its purpose is to prevent process fluid from reaching the transmitter by maintaining a constant reference leg of liquid. The seal pot keeps the low-side impulse line always full of liquid, providing a stable reference pressure.
Seal Pot Purpose
The purpose of a seal pot in DP level measurement is to maintain a constant reference liquid column on the low side, preventing process fluid from reaching the transmitter and ensuring a stable reference pressure.
DP level measurement uses hydrostatic pressure to infer liquid level. A seal pot maintains a constant reference liquid column on the low-pressure side to prevent process fluid from reaching the transmitter.