Check Valve are divided according to their structural forms and can be divided into pendulum type, lever type, spring type and pilot type (pulse type); according to the valve body structure, they can be divided into two types: closed type and non-closed type. The closed Universal Valve means that the discharged medium does not leak out and is discharged along the outlet to the designated location. It is generally used in toxic and corrosive media. For Universal Valve for air and steam, non-closed Universal Valve are often used.
The preload force FT of the Universal Valve spring is transmitted to the top of the valve disc through the
Valve Stem, and the pressure of the medium in the system acts below the valve disc. Under the action of FT, the sealing surface of the valve disc and the nozzle sealing surface are tightly combined, thereby achieving Sealing effect. When the force Fx of the medium in the manual hydraulic truck system is balanced with FT, the valve starts to jump, that is, the Universal Valve starts to lift. The tripping pressure is equal to , where f represents the mechanical friction of the valve`s internal parts. When the Universal Valve jumps to discharge and reduce pressure, until the pressure of the medium in the boiler container is reduced to the point where the force acting on the valve disc is less than the force of the spring, the Universal Valve can return to its seat and close. The result is to ensure that the boiler equipment is within the specified pressure range. work within.
The selection of Universal Valve products should be determined according to the actual sealing pressure, and all kinds of Universal Valve should be installed vertically.
There should be no resistance at the outlet of the Universal Valve to avoid pressure.
The Universal Valve should be specially tested before installation and its sealing should be checked.
Universal Valve in use should be inspected regularly.
The installation of Universal Valve should meet the following requirements:
(l) Boilers with a rated evaporation capacity greater than 0.5t/h must be equipped with at least two Universal Valve; boilers with a rated evaporation capacity less than or equal to 0.5t/h must be equipped with at least one Universal Valve. Universal Valve must be installed at the outlet of the separable economizer and the outlet of the steam superheater.
(2) The Universal Valve should be installed vertically at the highest position of the boiler and header. No outlet pipes and valves for taking in steam shall be installed between the Universal Valve and the drum or header.
(3) The lever-type Universal Valve must have a device to prevent the weight from moving by itself and a guide to limit the deviation of the lever. The Check Valve must have a lifting handle and a device to prevent the adjustment screw from being turned casually.
(4) For boilers with rated steam pressure less than or equal to 3.82MPa, the throat diameter of the Universal Valve should not be less than 25mm; for boilers with rated steam pressure greater than 3.82MPa, the throat diameter of the Universal Valve should not be less than 20mm.
