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In last articles we considered quite ordinary devices of direct act. Mechanical safety valves. Now we will get acquainted with the device of indirect act. Its design and mechanisms of work are more fascinating. Time the device not direct act, means, it should receive command from another. And this another should distinguish an emergency. As the signaling device the sensor usually acts, in most cases it is the pressure sensor.

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Fig. 1. Magnetic and spring valve.

That sensor fixes limiting value and gives a respective signal. Further, the valve, having received that signal should open. And it means, it should have own drive, which itself on for itself is not in dependence from a condition of a working environment. It is clear that it is most convenient to feed that drive with the electric power. The electric power is more universal type of energy though other options, but about them are probable a little later also. It is in most cases used electric or magnetic and spring valves. The electromagnet loads a lock, and the valve is blocked. When the electric power is disconnected, the electromagnet ceases to work, and the spring pushes out a lock, and the valve reveals. It is clear that such devices comfortably to use for automation, including creations of systems of home automatic equipment.
Discrepancy of that valve in quite bolshenny expense of the electric power. In particular, if it is established on the pipeline of a huge diameter, the electromagnet should create severe effort. Therefore exists and some other approach. The design leaves more difficult, it is called pulse the safety device, and turns on in own structure to a descent some valves. The magnetic valve in such device plays a supporting role, it is used on a small opening which does not possess the necessary capacity for emergency dumping.

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Fig. 2. Scheme of the pulse safety device.

Having received a signal from the sensor, that magnetic valve works, and the working environment arrives in special branch. And already from it it gets to the main safety valve. But, the working environment in this case represents itself as a hydraulic drive, and the main valve reveals. It is clear that such device is essential more expensively, but in certain situations its application is completely justified.
Continuation follows …