Abstract: The invention relates to apparatus and a method for the prevention of movement of a component which is provided in engagement, typically screw threaded engagement, with an article, one such article being a body of a valve assembly. The apparatus is provided in the form of a two part retaining device. One of the parts is engaged to the articles and the other part is located with respect to the component. The parts are provided with mutual engagement means, which, when engaged, are non rotatable and which, in turn, prevent relative rotation of the component with respect to the article.

Abstract: The invention relates to apparatus and a method for the prevention of movement of a component which is provided in engagement, typically screw threaded engagement, with an article, one such article being a body of a valve assembly. The apparatus is provided in the form of a two part retaining device. One of the parts is engaged to the articles and the other part is located with respect to the component. The parts are provided with mutual engagement means, which, when engaged, are non rotatable and which, in turn, prevent relative rotation of the component with respect to the article.

Abstract: A double block and bleed valve assembly having a valve body with a bore. The bore has an opened and closed position by two valve arrangements to control fluid flow along a pipeline.

Abstract: A valve of the double block and bleed type construction comprises a first valve assembly housing a first ball valve and a second valve assembly housing a second ball valve. The first and second ball valves are independently actuable between open and closed positions. Each of the ball valves are held within the particular valve assembly by an annular retainer component. Each valve assembly has a passage through which fluid can pass when the ball valve is in an open condition and also a mating surface which is brought to bear against the mating surface of the other valve assembly to form a valve with a single joint.