Abstract: A valve structure for an undersea pipeline including a valve cartridge received in a cage formed by a pair of thick parallel plates secured together by threaded studs. The studs entered in U-shaped rows down along the sides of the plate and in an arc near the bottom from side to side. There are no studs across the top. With the nuts loosened at one end of the studs, hydraulic rams, which connect the thick plates near the four corners thereof, may be extended to separate the plates slightly for removal and replacement of the valve module. Stop members prevent complete separation of the nuts from their studs.