Device to protect an air operated double diaphragm (AODD) pump from running dry or stalled, or for barrier protection

摘要

The device monitors the discharge pressure of an air operated double diaphragm (AODD) pump 2, changing its output if the monitored pressure rises above or falls below a set point to protect the pump under conditions such as running dry or dead-head (closed valve or stalled). The device may be a fully pneumatic adjustable pressure trip, comprising a floating diaphragm in a pressure chamber 1. The media side of the diaphragm communicates with the discharge line 4 of the AODD pump 2 while a controlled opposing air pressure is applied to the other side. A floating spool valve (14, fig.1) connected to the floating diaphragm gives a pneumatic pilot signal to a latching spool valve (5, fig. 1) which may include a visual indicator (6, fig.2) and a manual reset button (6, fig. 1). The latching spool valve may control a pump air supply valve 3. The device may monitor the pressure between the primary and back-up diaphragms of a barrier or containment type AODD (fig.6) to stop the pump if the monitored pressure becomes excessive thereby preventing uncontrolled discharge.