Nitrogen blanketing valve also referred to as a nitrogen padding valve or “make-up” valve, is the valve which filling the empty space of a liquid storage tank with nitrogen gas. The nitrogen seal device is mainly mounted on the top of the storage tank to control the micro-positive pressure of the storage tank, isolate the medium from the outside, reduce the volatilization of the medium, and protect the storage tank. Nitrogen blanketing valve uses the energy of the medium itself as the power source without additional energy. The control accuracy of the valve is about twice higher than that of the general pressure control valve, with a large pressure difference ratio (such as 0.8Mpa in front of the valve and 0.001Mpa behind the valve). That is convenient, fast, especially suitable for micro pressure gas control, which can be set continuously in the running state. Automatically controlled nitrogen tank blanketing valve has been widely used in the continuous supply of natural gas, city gas and metallurgy, petroleum, chemical industry and other industries.
How does the nitrogen blanketing valve work?
（1）Nitrogen blanketing valve closing piston sealing in the valve room, when the tank pressure is greater than or equal to the setpoint, membrane jacking up, make the gas pilot valve sealing ring moving up tightly by the spring pressed on the seat and closed to control the nitrogen imports. At the same time, special valve core chamber pressure increases and close to the nitrogen gas manifold pressure, the pressure through the internal channels from the special valve core chamber to the main valve core chamber. Main valve spool gas pressure balance, tightly closed under the double action of gravity and spring.
（2）Nitrogen blanketing valve in the open state, when the tank pressure is slightly lower than the set pressure, be because of induction pressure drop and move down the driving guide valve is opened, the nitrogen export through the orifice plate and guide valve in to the tank to tank pressure increases, and gas chamber pressure drop, pilot valve core nitrogen through the internal channels from the special valve core into the main valve core chamber. Since the piston area of the main valve core is greater than the seat hole area of the main valve, and because of the spring and the weight of the main valve, the pressure in the special spool chamber and the main valve spool chamber decreases very little when the tank pressure is slightly below the set point, the main valve remains closed and nitrogen enters the tank from the air valve.
The tank blanketing valve is the main component of gas tank blanketing device. Nitrogen blanketing device is composed of a control valve, actuator, pressure spring, conductor, pulse tube and other components, mainly used to keep the nitrogen constant pressure at the top of the container, especially suitable for all kinds of large storage tank gas blanketing protection system. The nitrogen supply device introduces the medium at the pressure measuring point on the top of the tank through the pressure tube into the detection mechanism to balance with the spring and the preload. When the pressure in the tank is reduced to below the pressure set point of the nitrogen supply device, the balance is broken, the valve conductor is opened, so that the gas in front of the valve passes through the pressure relief valve, the throttle valve, into the upper and lower membrane chamber of the main valve actuator, the main valve spool is opened, and nitrogen is injected into the tank; When the pressure in the tank rises to the pressure set point of the nitrogen supply device, close the valve core of the conductor due to the preset spring force, and close the main valve and stop the nitrogen supply due to the spring action in the actuator of the main valve.
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