Tank pressurization control for air carts

A valve assembly for an agricultural product distribution system, wherein the valve assembly is configured to be fluidly coupled between a storage tank and a primary line, wherein the storage tank is configured to store a granular product, wherein the primary line is configured to pneumatically deliver the granular product to an agricultural implement by guiding an air stream from a first section of the primary line with a larger cross sectional area to a second section of the primary line with a smaller cross sectional area, wherein the valve assembly is configured to selectively enable the air stream to flow from the primary line into the storage tank until a first static pressure in the storage tank is greater than a second static pressure in the second section of the primary line or a third static pressure in a meter housing by a threshold amount;

• wherein the valve assembly comprises a pneumatic valve, comprising:
• a fan inlet configured to be fluidly coupled to an air source configured to supply the air stream to the primary line;
• a tank outlet configured to be fluidly coupled to the storage tank;
• a shuttle comprising a shuttle hole;
• and
• a control pressue inlet configured to be fluidly coupled to the second section of the primary line or to a meter housing;
• and
• a diaphragm havin a first side and a second side, the first side coupled to the shuttle, wherein the first side of the diaphragm is exposed to the first static presure in the storage tank through the tank outlet, and the second side of the diaphragm is exposed to the second static pressure in the second section of the primary line or the meter housing through the control pressure inlet, wherein the diaphragm is configured to move toward the tank outlet such that the shuttle hole is aligned with the fan inlet when the first static pressure in the storage tank is not greater than the second static pressure in the second section of the primary line or the meter housing by the threshold amount.