Bellows 2 : The responsive element of a gas life valve. It performs the same functions the diaphragm operated valve. It provides an area for pressure to act on and to move the valve stem. (GL)
The Mudblogger (Oilfield, Energy and Related Photographs), Oil Field Glossary, TX, USA 2014. http://mudblogger.com/oilfield-glossary/, (Oil - Amer) {777}