Do breather valves and breather manholes serve the same purpose?
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Why are a breather valve and a breathing manhole installed together? Do they operate at the same time?
A breathing manhole (also known as a vent valve) operates on the principle of using a spring-loaded valve plate; breathing takes place depending on whether positive or negative pressure is present. The vent valve should have the ability to release both positive and negative pressures. Specifically, when the container is under positive pressure, the vent valve opens to allow gas to be released, thereby reducing the positive pressure； When the container is under negative pressure, the flame arrestor breather valve opens to draw in gas and relieve the negative pressure. This ensures that the pressure remains within a certain range, thus guaranteeing the safety of the container.
No, the breathing manhole opens to release pressure when the pressure is high; however, the breathing valve releases pressure when the pressure is high and fills it with pressure when the pressure is low
A breathing valve not only releases pressure; when the pressure inside the tank is insufficient, it also draws in air to prevent a negative pressure from forming in the tank, which could otherwise cause the tank to collapse.
It’s the same device, just with a different name.
They cannot operate simultaneously. Regarding pressure: the operating pressure of the breathing valve is slightly lower than the design pressure of the storage tank, while the breathing manhole generally corresponds to the design pressure (providing the final level of protection)； Regarding dimensions: the breathing valve is generally determined by the design institute, while the breathing manhole is usually 600 mm in size.
The same device, different names.
When operating under different conditions, in terms of design, the breathing valve is usually the first to activate, with the breathing manhole serving as the final safety measure. They both serve the same purpose.
Breathing manhole: In special situations such as too rapid increases or decreases in pressure, incorrect operations during the transfer of liquids, or excessively high flow rates, the flow rate provided by the breathing valve is not sufficient to meet the requirements, and the breathing manhole then comes into operation. Backup protection measures, which operate on the same principle as breather valves; they are generally available in DN500 and DN600 sizes. Sometimes in old tanks, you can also see hydraulic breathing valves; the principle is the same.