How to determine if a paint can has been completely depressurized?

1. Observe the pressure gauge: The most direct method is to check the pressure gauge on the paint can. If the gauge needle returns to zero or stays at the lowest mark, it usually indicates that the pressure inside the can has been completely released. For pressure gauges with color-coded zones (such as green, yellow, and red), the needle returning to the lowest point of the green zone also indicates that the pressure has been released.

2. Listen to the sound: During the depressurization process, listen to the sound from the can or pipes. When the pressure has been completely released, the booster pump or the inside of the can should stop emitting a continuous "humming" or airflow sound. If the sound completely disappears, the pressure has been released.

3. Check the valve status: Before opening the paint can lid or the paint filling port cap, you must confirm that there is no air pressure inside the can. You can try gently turning the lid; if you feel no resistance or hear a "pop," the internal pressure has been released.

4. Use auxiliary tools: For some systems, you can close the relevant valves (such as a two-way valve) and then observe through the vent pipe. If no high-pressure gas is ejected from the vent pipe, it indicates that the tank has been emptied and the pressure has been released.

Important Safety Note: Do not forcibly open the tank lid before confirming that the pressure has been completely released, as this may cause danger. If you are unsure about the pressure release status, it is recommended to contact a professional for confirmation.