A gas flow control valve configured to facilitate back-to-back mounting with a second, similarly constructed valve. The gas valve includes a valve body defining an inlet port and an outlet port, the inlet and outlet ports being surrounded by seal forming O-rings of different diameters. Flanges surrounding...http://www.google.es/patents/US6189568?utm_source=gb-gplus-sharePatente US6189568 - Series mountable gas valve
