The term "relief valve" refers to a regulating device for maintaining a liquid or gaseous medium at a desired level of pressure bypassing it through the pipeline bypass line. This pipe fitting automatically maintains the preset pressure difference between the inlet and outlet nozzles. When the value of the preset pressure at the inlet of the valve is exceeded, the valve opens, and when it drops below the set level, the valve closes. A complete discovery usually occurs when this number is exceeded by more than 20%.
Overflow valves for direct and indirect operation
Opening the bypass (regulating) valve element can be carried out by two types of actions - direct and indirect. The bypass valve, in which the action of the measuring element on the control valve is effected only by the energy of the medium, is called a direct acting device. They are divided into spring and membrane by the type of action on the bolt. In such valves, the opening of the shutter occurs under the pressure of the medium and is controlled by the compression of the spring. Direct-acting bypass valves are characterized by simplicity of the device, low cost and low sensitivity to pollution. The disadvantage is the maintenance of pressure with low accuracy. The bypass valve, in which the controller is externally influenced by additional energy, is called an indirect valve. These are more expensive and accurate devices.
When developing a turbocharger, engineers were faced with the problem of excessive pressure in the intake manifold. Rotation of the impeller turbine is due to the exhaust gases supplied to the blades, the amount and pressure of which depends on the engine speed. With fast driving the engine makes a large number of revolutions, the rotor speed of the turbine increases, creating excessive pressure in the intake manifold. As a result, the excess of forced air can lead to a so-called "blow-up", or "pompazhu", the engine and its failure. To solve this problem, a turbine bypass valve is installed on the turbochargers, which at a certain pressure releases the excess gas past the impeller into the exhaust manifold. This ensures normal operation of the engine and turbine without failures and failures.
The turbine bypass valve can be external and internal types. In most mass-produced commercial vehicles, an internal valve version is installed. External cars are completed, which require a large bandwidth and the possibility of additional adjustments (racing models). The external bypass pressure valve of the turbine is more reliable, but it has large dimensions.
Bypass oil valve
The bypass valve of the oil filter is activated when the pressure in the oil pipe between the pump and the filter element increases. This is due to increased oil density (for example, with cold start), filter wear or simply increasing the speed. When opening, the valve starts a part of the oil bypassing the filter. It is very important to select the valve with the correct opening pressure. It depends on this, at what speed the engine will be smeared with unrefined oil. It is not advisable to use a bypass valve with a low opening pressure, since a "dirty" oil will always flow into the engine at high speeds.
Characteristics of the bypass valve
The bypass valves are characterized by the following values:
- Coefficient of throughput - the amount of water flow (cubic m / h) at a temperature of 200 C⁰ and the estimated loss of pressure on the valve of 1 bar. This value is used to calculate the pressure loss in the system.
- Nominal pressure is the value corresponding to the maximum overpressure of the working fluid. The calculation takes into account the temperature of the medium for long and safe operation - 200 С⁰.
- Nominal diameter - inner side of connecting pipes. This value is used to unify the standard sizes of pipeline fittings. The actual diameter of the nozzle openings may be slightly different.
- Range of settings - the values of the limits of pressure differences supported by the bypass valve.