The burst valve can include a permanent magnet which holds a flap of the burst valve closed until the user inhales to produce the operational pressure difference.

The pressure at the face port opens up the main valve poppet and opens the channel.

The hydraulic pressure from the end directly overcomes the spring force and drives the valve poppet up and opens the channel.

There is a small hole on the side of the main valve poppet, connecting the side port and the spring chamber.

A rocker, a backstop ring, a hermetic gasket and a press cover are sleeved on the spindle, the rocker is connected with valve flapper by flap shaft, and falve flapper is connected with the spindle by the rocker.

The valve flap (107) is affixed on an upstream valve bore portion side of the valve shaft (121), wherein incoming fluid presses the valve flap (107) against the valve shaft (121).

This valve (8) is preferably a reflux valve.

A surface controlled subsurface safety valve ("SCSSV") assembly has primary and secondary valves, typically an upper and lower flapper valve.

Pilot valve means (24) are provided which comprise valve body means (70) and valve shuttle means (76).

The vane (5) of the butterfly valve is provided with a rotary butterfly valve (7) of smaller diameter, the latter valve being opened and shut independently of the larger valve.

A valve port (14) is opened and closed by the ball valve (2).

.6 The delivery valve of each fire pump shall be fitted with a non-return valve.

Preferably, the safety valve includes a hydraulic conduit bypassing the flapper valve to allow communication therethrough when the valve is closed.

A temperature-responsive member (20, 21), operatively coupled to a valve plug (34), is used to control the position of the plug (34) relative to a valve seat (30).

The refuelling connection or receptacle must be integrated with a non-return valve or a valve with the same function.