A conveying system for injecting material at a convey line pressure is disclosed. Material is injected into the convey line through a feed device from a pressurized vessel pressurized at the convey line pressure. In illustrated embodiments, the vessel is pressurized at the convey line pressure through connection to the convey line. As described, the vessel is connected to the convey line through a pressurization line to pressurize the vessel at the convey line pressure. In illustrated embodiments described the pressurization line is opened and closed via a valve to control pressurization of the vessel at the convey line pressure. In illustrated embodiments, convey line pressure is applied to multiple vessels of a conveying system through one or more pressurization lines to inject material into the convey line.