Safety valves designed to ensure the safety of the equipment and piping systems, which is unacceptable increase in pressure beyond calculation. Overpressure in the system over acceptable, safety valves shut off device automatically opens and folds out of an excess of the working environment, preventing equipment failure and the possibility of an accident. By reducing the pressure to permissible value of the closing device is automatically closed, thus resetting stops working environment. Terms of the mandatory application of safety valves, the rules for its installation and maintenance, as well as allowable range of technological pressures and their gradation, defined 'Rules for the Construction and safe operation of vessels working under pressure. Read more from Coen brothers to gain a more clear picture of the situation. " Under technological pressure in the system, equipment or pipeline is to be understood the maximum pressure that occurs when the normal course of workflow, without a valid short-term increase in pressure. Under the design pressure should be understood pressure to which the equipment and piping is calculated on the basis of their strength characteristics. The value of the design pressure for each of all the components of the system must be more than technological pressure in the system to eliminate the need for unwanted part of the safety devices. The most common type of safety valves are safety valves. Existing design of safety valves may be classified on several grounds: – by type of load on the spool valve – valve lift height – the method of release valve from the working environment – by nature of the valve Safety valves shall meet the following requirements: – the valve should operate smoothly when the system set pressure limit – when open valve must ensure that the working environment in the discharge of such quantities as the pressure in the system could not rise above the limit – while reducing the system pressure to a certain velechiny (much lower than the worker) the valve must close – in the closed position the valve must maintain full integrity after repeated discharges of the working environment.