Action to maintain the airtight tank; gas space when the tank pressure increases, breathing valve to control pressure, the pressure valve is open the top, the gas escaping from the tank so the tank pressure does not continue to increase; when tank gas space pressure drops, breathing valve to control the negative pressure, the atmosphere outside the tank top to open the vacuum valve and into the tank so that tank pressure does not continue to decline. 
 Shanghai Tang Yang breathing valve product: CB-T692-94 double-tank breather valve, HDX-1 双 mouth breathing valve, HXF1 Pipe breathing fire and explosion protection valve, HXF-88 new breathing valve, HXF type with suction over breathing valve, QHXF-2000-type antifreeze breathing valve, QZF-89-type all-day frost fire retardant breathing valve, ZFQ type of fire retardant breathing valve, stainless steel breathing valve, with take over the breathing valve, with double-take over the breathing valve, explosion-proof fire retardant breathing valve, jacketed insulation breathing valve, all-weather antifreeze breathing valve, all-weather fire breathing valve, all-weather oil tank breather valve, pressure vacuum breather valve, automatic ventilation control valve 
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