(1) the working medium in the pressure vessel or pipeline is viscous or easy to crystallize and polymerize, and it is easy to stick or block the safety valve disc and base;

(2) the chemical reaction of materials in the pressure vessel may cause the pressure in the vessel to rise sharply and the safety valve cannot open the place for pressure relief in time;

(3) the working medium in the pressure vessel or pipeline is highly toxic gas or expensive gas, and the safety valve may be used in places where leakage may lead to environmental pollution and waste;

(4) places where pressure vessels and pressure pipelines are required to be completely discharged or unimpeded when fully discharged;

(5) other places not suitable for safety valve but suitable for bursting disc.