CHECK VALVES
The check valves ( see fig. 1) are used to control the flow through them – they block the flow in one direction and allow it in the reverse one. Frequently used schemes of connection are presented below in fig. 2:
The check valves in the production list of HIDROPNEVMOTEHNIKA AD include:
KO-… type –poppet valves with spool lock and a spring, which acts in the direction of closing the valve and determines the pressure, at which the valve will open. They are mounted in bodies for in-line assembly in the hydraulic systems.
LINE RUPTURE PROTECTION VALVES
Line rupture protection valves are mounted in hydraulic systems, driving cylinders or hydraulic motors, used to lift heavy weights. When a pressure hose, or a pressure pipe to the cylinder (hydraulic motor), is ruptured, the movement of the unit is accelerated under the force of the weight which acts in the direction of its descending. This may lead to serious damages to the installation, and to unwanted oil leakage as well. The role of the line rupture protection valve in this case is to close the flow of oil in the direction from the cylinder to the system. The valve is adjusted to close when the flow through it is increased with 15...20 % more than the volume during the normal work of the system. In this way the valve will be activated only when there is a breachin the integrity of the pipes from the valve to the tank, as this is the moment when a reduction of the pressure drop to the tank occurs and the flow is increased over the volume calculated for the normal work of the system. In certain cases it is advisable not to lock the cylinder when it breaks down, but to retract it slowly to its initial position under the pressure of the weight. To achieve this, a hole is drilled in the dish of the valve. The diameter of this hole determines the speed of descending after the valve is closed. The existence of such a hole changes the graphic of the valve adjustment. You can contact us for a more precise selection of the parameters. When a valve is mounted, it is advisable to comply with the following rules:
- the valve can close when the adjusted flow of the fluid is exceeded only in one of the directions of this flow. In the other direction the flow of the fluid cannot lead to a closure, irrespective of the volume of the flow. The direction of closure must be from the cylinder to the system.
- whenthe cylinder performs an action only in one direction, it is enough to mount only one valve in its discharge end.
- the valve must be mounted directly on the threaded feeder of the cylinder (under the orifice). To make that possible it is made with a longer thread or within a body, screwed in the feeder.
END OF STROKE VALVES
The end of stroke valves are hydraulic valves used to indicate a certain position of the movement of an actuator. Most often these are 2- way valves.To activate the valve the pushermust be pressed , thisallows the oil to pass through the valve if it had been closed before thator blocks the oil if the valve had been open. The end of stroke valves can be used as pilot valves, in which case the flow is used to hydraulically activate other valves of the circuit, or as valves for direct control, for example to unload the flow of the pump to the tank. In general the activation of the valve is achieved by a hump with a certain profile. To provide a problem-free work of the end of stroke valve, it is good to reduce the movement transmitted from the hump by a roller mechanism. In this way only an axial force will be conveyed to the pusher.
