What problems can occur with a sending vessel?

In addition to the fact that transmission vessels must be designed and built to a recognized design code, there are three basic design parameters that can affect transmission vessel performance:

• Cone angle
• Vessel volume
• Vessel pressure

The increased use of transmit vessels for feeding materials with "poor" flow properties requires the selection of an appropriate cone angle. Vessels with incorrectly designed cone angles will lead to "ratholing" or "bridging" problems (see figure below).

Ratholing results in the formation of a blowhole through the material mass and once formed it is no longer possible to transport material. Bridging causes the product to form a barrier across the outlet of the vessel, preventing further material flow. The selection of a suitable cone angle can be facilitated by the use of the classic design criteria for silos or hoppers. However, these design criteria do not take into account the fact that the product is under high pressure and in certain situations gas also seeps through the material. Currently many of the selection criteria for cone angles are based on empirical data obtained from experience.