The mathematical model of a pilot operated pressure relief valve is described by a large system
of nonlinear differential and algebraic equations. To analyze the stability condition of the valve,
linearization of the mathematical model and getting the transfer function, i.e., the characteristic equation of
the system is necessary. Obtaining the transfer function with elimination of the intermediate parameters is
very complex and sometimes impossible. In this paper, a state space matrix method is used to reduce the
large system of equation and to get the transfer function of the system
