safety valve Series PV 1509
Description
Body is angle, with possibility of either flanges on both ports, or weld ends or combinated. Inlet port is of a nozzle type, outlet port is extended. There are welded lugs on the valve body for gripping the valve to the load-bearing structure and absorbing reaction forces. Plug, equipped with an additional flat for achieving of stronger lifting force, is pressed by the means of the spring and pressure air cylinder to the seat. There is a double differential piston moving inside of pressure air cylinder to which the lifting and loading airs are supplied through the hoses from the control unit. The valve is set and adjusted by its producer to the opening pressure specified in the customer´s order. Such a setting is secured against an unallowable interference. Dimensions of connection flanges and weld ends are specified after the agreement between the producer and customer when the order is being technically cleared. Standard weld ends correspond to ČSN 13 1075 (3/1991), standard flanges correspond to ČSNEN1092-1 (2/2003) possibly ČSN13 1060. The valves PV 1509 correspond to ČSN EN ISO 4126-5.
Application
The full-lift safety valve with additional loading is a valve designed for automatic protection of a pressure equipment (steam boilers, pressure pipelines, steam-conditioning stations, pressure vessels, turbine extraction etc.) against unpermitted pressure increase over allowable limit.
The valve output guaranteed in accompanying documents is guaranteed only provided that the pressure loss in pipeline does not exceed 3% of opening pressure in inlet pipeline and 25% in outlet pipeline.
The safety valves PV 1509 are designed for water vapour, air, and non-aggressive gases and vapours. The highest temperature of securing medium is up to 600°C. The valves can operate continuously in dust environment with ambient temperature to 80°C. After consulting the producer, it is possible to pipe the valve in environment with ambient temperature below zero. The opening pressure range is specified in the "Technical data" table.
The valves are delivered and must be operated together with their accessories, i.e. control unit and aerating system. Single parts can be delivered only in case of the replacement for previously delivered equipment.
Valve function
The safety valve is controlled by its control unit. If the control unit is for any reason put out of service, the valve may be shortly operated just exceptionally or in case of emergency (pressure air supply failure, control unit breakdown etc.). Any longer operation or repeated service in such state may lead to a rapid reduction of the valve service life due to vibrations and leakage.
After reaching the opening pressure value, control unit lets the air out of the space above the piston of pressure air cylinder (loading air) Air pressure from below the plug (lifting air) plus securing medium pressure acting on the plug overcome spring force and safety valve then rapidly opens to its full lift. When the pressure drops, then whole action runs reversed. Rapid opening and closing are just two main preferences of the valves .The valve reaches full opening after the pressure of securing medium increases by max. 3% above the value of set opening pressure (pset). The valve becomes tight closed after the pressure of securing medium drops by max. 5% below the value of set opening pressure (pset).
In case of control air pressure supply failure, the force is induced by the securing medium pressure only. The valve opening runs incomparably more slowly than in the previously described state. As a result of it, the seat is excessively stressed and may get worn. The valve becomes fully open when securing medium increases by mx. 5 % above the value of set opening pressure (pset). The valve becomes tight closed when securing medium pressure drops by max. 10% below the value of set opening pressure (pset).
