A safety device for closure elements (1) on pressure-medium-containing tanks, in particular on hydropneumatic devices such as hydraulic accumulators, has a screw connection provided as a closure device on a filling or checking port. The screw connection has a closure screw (1) threadedly engaged on the port (3) and blocking the port (3) when the screw connection is tightened and opens the port (3) when a flow path is released. A device (25) limits the free movement path of the closure element (1) when moved out of a closed position as a result of occurring overpressure.

A bladder and attachment member assembly for use with a container comprises an elastomeric gas-filled bladder comprising a valve stem. A first attachment member is disposed over the valve stem within the container with the bladder. A second attachment member is disposed over the valve stem and over the first attachment member. The second attachment member is outside of the container interposed between the valve stem and a container opening. Rotational movement of the valve stem is fixed relative to one or both of the first and second attachment members. In an example, the valve stem comprises one or more surface features that register with one or more surface features of the first and/or second attachment member to thereby fix relative valve stem rotational movement. In an example, the valve stem surface feature is a flat surface that registers with a flat surface of the second attachment member inside diameter.