Relief valve device

A valve assembly includes a fluid support valve, in the form of a poppet valve for use downhole to maintain a column of fluid above an electric submersible pump, above which is mounted a relief valve, in the form of a sleeve valve, to enable fluids such as injection fluids to bypass the fluid support valve. A spring 6 biases a poppet 4A against a seat 3 and also biases a ported sleeve 7A to a first position in which the relief ports 14A do not align with ports 15 on housing 2 until the fluid pressure above the valve assembly acting on push rod pistons 9A reaches a cracking pressure and moves the sleeve 7A to a second position in which ports 14A and 15 are aligned.