Abstract: The invention provides an improved pipeline pulsation dampener, including a pressure vessel divided by a diaphragm of elastomeric material into first and second pressure zones. The first pressure zone is connected to a pipeline and receives any undesired pressure changes in the pipeline through a first flow passage in the pressure vessel, while the second pressure zone receives a second fluid at a preselected pressure. The diaphragm has a reinforcing insert for bridging the first flow passage to support the diaphragm when the pressure of the second fluid in the second pressure zone exceeds the pressure of the first fluid in the first pressure zone to restrain the diaphragm from extruding through the first flow passage. The reinforcing insert is encased in the elastomeric material of the diaphragm to prevent the insert and the bond between the elastomeric material and the insert from being exposed to the fluid being pumped.