How does a sending vessel work in pneumatic transport?

A fully automated sender and blow vessel works as follows (see image below)

• The vent valve (A) is opened to reduce the pressure of the vessel.
• After a short delay, the material supply valve (B) is opened and the filling process is initiated.
• The material will flow into the drum until the high level (HL) indicator is activated.
• The high-level indicator (HL) activates a signal to close the valves (A) and (B).
• After a delay, the air supply valve (c) is opened to add air to the vessel.
• Air is fed into the vessel until a preset pressure in the vessel is reached.
• A pressure switch (PS) is activated which in turn sends a signal to open the drain valve (D).
• Material is fed until a low pressure signal is detected on the pressure switch, indicating that all material has been transported.
• Normally, the air supply is maintained for a short time to ensure that any material remaining in the pipe is transported to the receiving station.
• The cycle is then restarted.