Tank pressurization control for air carts

A pneumatic distribution system configured to distribute a granular product to an agricultural implement, wherein the pneumatic distribution system comprises:

• a primary line configured to pneumatically deliver the granular product to the 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;
• an air source fluidly coupled to the first section of the primary line, wherein the air source is configured to output the air stream;
• a secondary line fluidly coupled between the first section of the primary line and a storage tank configured to store the granular product;
• a valve assembly disposed along the secondary line, fluidly coupled between the storage tank and the primary line, wherein the valve assembly comprises:
• a fan inlet fluidly coupled to the air source;
• a tank outlet fluidly coupled to the storage tank;
• a shuttle comprising a shuttle hole;
• a control pressure inlet fluidly coupled to a meter housing;
• and
• a diaphragm having a first side and a second side, the first side coupled to the shuttle, wherein the first side of the diaphragm is exposed to a first static pressure in the storage tank through the tank outlet, and the second side of the diaphragm is exposed to a second static pressure in 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 meter housing by a threshold amount.