Ask about the function of a breathing valve
Thread Content
Recently, I was working on a wastewater regulation tank. The tank has a capacity of 500 cubic meters and contains wastewater. Environmental inspections stated that it’s not allowed to discharge wastewater directly through an open top like this. I installed two vent valves on the tank. I’m concerned that the fan in the existing exhaust treatment system might overwhelm these vent valves. Since it’s a tank that’s over 20 years old and operates at atmospheric pressure, I placed a cover over the exhaust ports of the vent valves, leaving air inlets at the bottom on both sides. The fan’s intake ducts draw air in through this cover. As there is no nitrogen seal valve, air needs to be supplied through the vent valves when wastewater is discharged. I’m wondering whether the vent valves can supply air in such a frequent or prolonged manner
The forum is quite quiet these days. I also want to know if the vent port of the breathing valve is one-way
The function of a breathing valve is to balance the pressure in the storage tank as internal pressure changes, preventing damage to the tank due to large differences between internal and external pressures. It also helps to reduce the leakage of steam from the tank, thus protecting the environment. If the sewage discharge requires air supply through a vent valve, then the vent valve must be able to handle frequent or prolonged use. However, it is necessary to ensure that the flow and pressure settings of the breather valve meet the requirements for the proper operation of the storage tank. If you are concerned that the fan may affect the proper functioning of the breathing valve, it is best to have a professional assess whether the system design is appropriate. .
Breather valves are primarily used to address the issues caused by thermal breathing in storage tanks and changes in air pressure resulting from liquid inflow and outflow. As you mentioned, regarding the 500 m3 storage tank, page P1020 of the process design manual states that the heat absorption rate is approximately 84.5 m3/h, while the heat release rate (for flash points > 37.8°C) is 50.7 m3/h ； The ventilation volume for inflow and outflow fluids ≤ 130 m3/h ； Therefore, I believe that when arranging for exhaust fans to remove air as you have done, it is necessary to consider the breathing capacity of the breather valve. If the suction capacity after the modification is not sufficient to meet the maximum requirements for liquid inflow/outflow or thermal breathing, I think there is a risk involved. Furthermore, a breathing valve remaining open for an extended period or opening frequently is not a design issue; it is a quality issue with the valve.