Principle
1. A U-tube manometer consists of a U-shaped transparent glass tube filled with liquid (such as water, mercury or alcohol),
with its two ends respectively connected to the system under test and the atmosphere or two pressure measurement points.
2. When pressure acts on one end, a height difference is formed in the liquid level. The pressure value can be calculated by
measuring the difference in liquid levels on both sides. If the liquid level at one end drops, it indicates positive pressure; conversely,
it indicates negative pressure.
Operating Steps
Preparatory work: Ensure that the pressure gauge is placed vertically, check for no leakage, and the liquid is clean and fully filled.
Connection system: One end is connected to the pressure measurement point of the boiler, and the other end is open (for pressure measurement)
or connected to another pressure measurement point (for differential pressure measurement).
Reading method：
1. After the liquid level stabilizes, read the liquid levels on both sides (using the tangent line at the top of the meniscus as the reference).
2. Calculate the height difference (in millimeters), and convert the pressure value based on the liquid density.
Cautions
Range matching: The measured pressure must not exceed the upper limit of the pressure gauge.
Vertical calibration: Inclination will cause reading errors. The U-shaped tube must be kept vertical.
Liquid selection: Choose the appropriate liquid based on the pressure range (use mercury for high pressure and water or alcohol for low pressure).
Maintenance: Clean the inner wall after use and seal the pipe opening to prevent contamination.
