The occurrence of emergency situations in systems operating under pressure has a high probability of occurrence, therefore, such systems need to be protected from excessive overloads in pressure. An effective solution is to use safety valves. The design and general characteristics of the elements may vary depending on the type of installation (liquid or gas). As a result, you need to choose the appropriate fittings.
Purpose of safety valves
The safety valve is used to protect the system from excessive, increased pressure and to prevent destruction or damage to the system. When the pressure limit is exceeded, the valve discharges the excess outside the working medium value. After the pressure is normalized, the valve is closed and the discharge is stopped.
The locking element, under the influence of a spring, is pressed against the seat. As the pressure increases, it overcomes the overall compressive force of this spring. The locking element is moved away from the seat by squeezing. All the excess gas or liquid rushes into the freed space. At the moment of release from the excess, the pressure begins to decrease, and the locking element is pressed in the opposite direction under the influence of a spring.
After closing the device, it is ready for the next cycle. The compression threshold and the compression force are regulated by a special screw.
Safety valves and their classification
The device is classified according to a number of parameters.
On the basics of the principle of action:
- Direct operating principle-mechanical, classic valve;< / li>
- Indirect principle of operation-here are used: remote-controlled valve, automatic control and pressure sensor The valve and the sensor can be located in opposite places of the structure;< / li>
By the shutter opening method:
- Two-stage (for gases);
- Proportional (in molosgiaemykh< / span> working environments);
By the way the spool is loaded:
There are also many other types of emergency safety devices available.
Design features and differences
Most valves are available with only one seat, although some elements may have two seats or two rods with springs.
Differences can be found in the lifting height in the locking element in relation to the diameter:
- Full lift-over 1/4;
- Low lift – over 1/4;
- Average rise – up to 1/20;
The device will work much faster if the degree of lifting is higher. Low-lift</span > valves are used in places where there is no need to discharge large volumes of liquid. There, the lifting height will be similar to the volume of the medium. Full-lift < / span> the element has two positions «Closed» and «Open» and they are called two-position. Such devices are designed for:
- Liquid systems with high pressure;
These structures are used in special and critical areas.
The spring valve is common in heating, water heating, and water supply systems. The spool is pressed directly against the seat of the compressed spring. By means of a screw, the spring can be adjusted to different limit values. Some devices are equipped with a lever of the forced shutter, for its quick opening in case of emergency situations and check of operability. This is excluded in harmful industries. The valve elements are covered with a special anti-corrosion coating.
The stem, which passes through the housing, is sealed by means of a double oil seal and prevents the penetration of harmful substances.
Such elements can be mounted in an exclusively reserved position relative to the horizon. This provision is strictly regulated by the manufacturer. They are not intended for installation and operation on movable objects. The basis of the principle of their work is the use of gravity to counteract the force of pressure.
Such a lever can enter into resonance and create vibrations. The overall dimensions of the loads and levers may increase if the pressure value is high. The two-seat valve will help to get rid of vibration. They do not age the springs, and the operating parameters are extremely stable.
These are products of indirect action. Solenoid is actuated by a locking element. The magnet presses the solenoid to the seat, and when the maximum pressure level is reached, the automation itself turns off the voltage. The valve is opened by pressing the medium and pressing the spool. In another version of the design, the push-up occurs by means of a spring and by turning on the solenoid when the limit value is reached. There are other types of this valve.
The advantage of the product is that it does not set the threshold value by accessing the valve. In the management, the program settings change depending on the stage of the technological process. Such devices are more expensive than analogues, but pay for themselves when used in production.
The requirement for the device is based on clarity in operation and reliability in use. This can be achieved by:
- Guarantee of tightness;
- Quick opening;
< li>Clear closing;
- High throughput;
- Trouble-free operation;
Direct-acting safety valve AO OZNO
The fittings are regularly tested for integrity, operability, and the quality of the seals is also checked. Verification is carried out in a test center or a specialized laboratory. On-site inspection can be performed for elements operating in complex environments and complex installations. Here is the test method in action.
Standards and rules
The valve is applied on the basis of the operating rules, industry standards and operating rules.
In places where the vessels operate under pressure, the following documents apply:
- GOST 24570-81 national standard in respect of safety valves;
- PB 53-576-03;
- «Boiler & Pressure Vessel Code«;
When selecting an element, it is necessary to determine the main limit values in the pressure. The following parameters should be considered:
- Circulation Feature:
- Pump or boiler capacity;
- Operating temperature and volume of the working medium;
Based on these parameters, specialists make a choice which valve should be installed. The technical characteristics of the element are taken into account. So, the spring valve is ideal for the heating system. Medium and low lift products are ideal for liquid environments. The throughput capacity should allow the pressure to be reset to the desired values. Open valves are suitable for the discharge of excess into the environment, and if drainage is used, then nipple or threaded.
It is strictly forbidden to buy an item with an inflated trigger threshold. Such a device can cause damage to the entire system, as there is a risk that it will not open at the right time.