Safety valve, spring-loaded, full-lift, angular, ENJL1040 PN 40/16 flanged 35.902 ARI-SAFE DN25/40 PN 40/16 Pcr=16.0 bar
- Safety valves Ari-Armaturen ARI-SAFE 35.901
- Construction 12903 RU - PN 16 DU - DN 20-DN150
- Material - EN-GJL-250, EN-JL1040
- Connection - Flange
- The shape is Angular
- Temperature *housing - -10 °C to300 °C
- Characteristic - spring-loaded rn cone with flexible seal rn bellows made of EPDM
- Construction 12903 RU - PN 16 DU - DN 20-DN150
- Material - EN-GJL-250, EN-JL1040
- Connection - Flange
- The shape is Angular
- Temperature *housing - -10 °C to300 °C
- Characteristic - spring-loaded rn cone with flexible seal rn bellows made of EPDM
- Areas of application: heating installations
- Media: water vapor
A safety valve is a valve used in pipelines to protect the system from mechanical failure under excessive pressure.
The principle of operation of the safety valve is to release excess gaseous, vaporous or liquid media from vessels and piping systems into the outlet pipe when the pressure rises above the established norm.
By the nature of the action, safety valves of direct and non-direct action are distinguished.
Direct-acting valves usually have a spring-loaded opening and closing mechanism. That is, the compression resistance of the valve spring corresponds to the set mark of the maximum allowable pressure in the system. While the pressure is within the normal range, its force is not enough to compress the spring - the safety valve is closed, that is, "does not work". When the pressure rises above the norm, the spring compresses, opens a gap in the outlet pipe to discharge the working medium - the valve "works", reducing the critical pressure in the system to normal.
The operation of safety valves of non-direct action is provided not by the medium, but by extraneous sources of influence - pulse safety devices, which, in turn, react to an increase or decrease in the pressure of the working medium.
A safety valve is a type of pipeline fittings, an automatic mechanism designed to protect closed duct (pipeline) systems, devices, machines and containers installed in them from damage by excessively high or low (vacuumed) pressure. The protection of a closed thermodynamic system by a safety valve is carried out by dumping (during vacuuming – suction) part of the working medium.
Unlike irretrievably collapsing safety (bursting) membranes, the automatic safety valve mechanism ensures that the discharge of the working medium is stopped when the emergency pressure in the circuit is normalized to a safe (operating) value. Thus, operable safety valves simultaneously save:
- valuable working equipment from emergency damage;
- the working environment from an unreasonably large discharge, which is very important in situations where the working environment itself is of great material value;
- supported technological and economic processes from abnormal interruption.
DEVICE AND PRINCIPLE OF OPERATION
The classical scheme is considered to be the design of a direct-acting spring safety valve. Its mechanism is carried out in its own housing, with inlet and outlet pipes assembled. The valve body has an internal passage channel, usually angular in shape (but there is also a direct-flow version). The valve mechanism consists of a spool (gate) with a guide rod, which is pressed by a setting spring (setpoint) to the seat on the inlet channel of the housing. The actuation pressure of the safety valve is determined by the clamping force of the control spring, which can be adjusted:
In the operating position, under the influence of the force of the driving spring, the safety valve is always closed (its shutter is pressed against the seat). The pressure of the working medium through the inlet channel acts on the gate plate, but cannot overcome the clamping force of the master spring.
As the pressure in the system increases, its resistance to the downforce of the spring increases. When the pressure in the system reaches a threshold (emergency) value, it overcomes the force of the setting spring, the spool (gate) rises above the seat, opening a passage slot through which a massive discharge of the working medium (and, accordingly, excess pressure in the system) begins through the outlet channel and branch pipe into the discharge system. After the excess pressure in the system is relieved and normalized to a safe value, the force on the valve gate from the working medium is reduced, and under the influence of the setting spring, the spool plate (gate) is pressed against the seat again, thereby closing the valve and stopping the mass discharge of the medium.
It should be borne in mind that the closing pressure of the safety spring valve (direct action) will always be 10-15% less than the threshold value of its operation (opening). This is due to the need to overcome the dynamic (kinetic) counteraction from the flow of the discharged medium by the force of the setting spring.
In some cases, the safety valve may be equipped with a forced opening mechanism (usually a lever type), which is used to check its operability. Such a forced check of the valve is used to prevent it from sticking, sticking, freezing, as well as for preventive purging. But in cases of duct systems with high operating pressures and temperatures, aggressive and toxic working environments, activation of the forced valve opening mechanism can be dangerous. Safety valves with a forced opening mechanism are not used for such systems.
TYPES OF SAFETY VALVES
According to the principle of operation, safety valves are:
- Direct action – when the opening and closing of the valve occurs as a result of direct action on its mechanism by excessive pressure in the system. The classic spring valve belongs to just such a type.
- Indirect action – when the valve is opened and closed by a controlled servo (usually electromagnetic), which receives signals for opening and closing from third-party sensors.
According to the type of lifting mechanism of the gate, there are safety valves:
- spring-loaded;
- cargo (lever-cargo);
- combined lever-spring;
- combined magnetic springs.
Depending on the lifting height of the valve gate plate above the seat, safety valves are distinguished:
- low-lift, where the lifting height of the shutter plate does not exceed 1/20 of the through diameter of the seat;
- full-lift, where the lifting height of the shutter plate reaches ¼ and more of the through diameter of the seat;
- medium-lift, where the lifting height of the shutter plate is in the range from 1/20 to ¼ of the through diameter of the seat.
By the nature of the operation of the lifting mechanism, safety valves are:
- proportional action – when the lifting height of the valve plate is proportional to the degree to which the pressure threshold is exceeded;
- two–position action - such valves, when triggered, immediately open to the entire flow section, thereby accelerating the discharge of the working medium and normalization of pressure in the system.
POPULAR DESIGN OPTIONS FOR SAFETY VALVES
- With high performance, these are, as a rule, full–lift valves of two-position action, with a large through-section of the seat, which provide rapid mass discharge of the medium and normalization of pressure in hydraulic systems with a large volume and flow of the working medium.
- For bypass (bypass) – it is used to maintain the pressure in the system at a constant level, by continuously diverting (overflow) the medium into the drain (drainage) pipeline.
- Compact design – due to the use of modern materials and mechanisms, more compact valve sizes are achieved, for use on small-sized and low-volume (low-performance) equipment, or in systems (devices) for household purposes.
- For sterile conditions, the design uses advanced systems and materials for sealing and sealing, in order to prevent leakage of the working medium into the surrounding space, and mixing of the environment into the working environment.
- For aggressive media – in the design of such valves, in addition to ensuring a high degree of tightness, chemical resistant structural and sealing materials are used that can withstand the destructive (corrosive) effects of aggressive working environments.
- API standard valves are structurally made in accordance with the technical requirements of the North American Petroleum Institute (API). The use of API standard technology will be required on samples of imported hydraulic engineering equipment from the USA and other countries using this popular production standard.
- Pilot valves are indirect–acting, with an electromagnetic servo for opening and closing, controlled by signals from third-party sensors. As a rule, they are used in complex hydraulic engineering systems with programmable (computer) control of operating modes. Usually, pilot valves have, along with the pilot (servo), and a direct spring drive, in case of power outages, or a malfunction of the servo power supply for another reason.
SCOPE OF APPLICATION
The scope of application of safety valves can safely include all duct (pipeline) systems for industrial, commercial or technical purposes, regardless of their size, technical parameters, location, man-made hazards. Since almost all of them need emergency protection in case of possible work overloads, breakdowns of working equipment, third-party effects on the system, and other emergency situations.
The use of safety valves makes it possible to localize and limit, and often neutralize (prevent) the destructive effects of an emergency, and ultimately save valuable machinery, equipment, and partially the working environment. As a means of protection, safety valves have an advantage and priority in application over safety (bursting) membranes, thanks to their drive mechanism, which makes it possible not only to automatically open, but also to close the discharge channel. As a rule, safety valves are used in conjunction with bursting membranes. And in systems with a small volume or consumption of the working medium – and independently.
TECHNICAL REQUIREMENTS FOR SAFETY VALVES
The main technical requirements for safety valves are:
- ensuring the required degree of tightness of the system in the closed state;
- guaranteed reliability of the mechanism operation when the pressure in the system reaches the threshold value;
- providing the necessary bandwidth for rapid mass discharge of the environment from the system, in order to maximize the limitation of the emergency situation (condition) in time of action;
- ensuring timely closure of the valve when the pressure in the system is normalized to a safe (working) level;
- ensuring the stability of the valve's operating parameters (actuation and closing forces, tightness) throughout the standard service life.
Safety valves belong to the list of equipment that is subject to periodic inspection in a specialized laboratory or organization (such as a boiler inspection), periodic testing in operation on a test bench.