Check valves - design, purpose and application
Check valves are an example of the simplest automatic devices in valves. Check valves owe their appearance to the need to control the direction of the flow of the working medium in pipelines (devices), or rather, to ensure the movement of the medium in only one direction. By its functional purpose, the check valve is very similar to the diode used in electronics - it is not for nothing that they are indicated by similar symbols on the diagrams. In pipeline automation, despite similar tasks, check valves can be structurally different. Let's look at some of the more common options.
The sleeve check valve is familiar to many (and not only to sellers and installers of fittings) for its simplicity and reliability. As a rule, this check valve has a turned brass body with internal threads on the edges, in which is located a shut-off assembly in the form of a disk with a guide shaft, a rubber seal and a stainless steel conical spring. The locking disc with guides can be made of plastic (and in more expensive valves - of brass) - it is an executive body that closes the section when the direction of the medium flow changes under the influence of a return spring.
Here are some home applications for spring check valves:
- together with a pump for pumping liquids from reservoirs or containers
- in pumping stations for water supply to consumers - to cut off the static pressure of the accumulator from the cavity of the pump impeller after it is turned off
- in wells - together with a deep submersible pump, which ensures instant water supply after turning on the pump
- in quick couplings of irrigation systems
- in air vents of heating systems.
Gravity check valve (valve for bypass of the heating system with natural circulation) is a special automatic device designed to open the main supply line when the circulation pump stops (breakdown) and eliminates the possibility of boiler overheating (especially important for solid fuel boilers, as there is no possibility coolant temperature adjustment). The check valve for the heating system, as a rule, does not contain a return spring and a rubber ball of increased buoyancy is used as a shut-off element, which, in the absence of a coolant flow from the pump, pops up and opens the section for natural circulation. There are only two types of valves for circulation pumps on the Ukrainian markets - the so-called cast-iron “Polish” (or rather, Chinese) with a rubberized steel hollow ball, assembled from two hemispheres on screws and Ukrainian production, manufactured by STA (Kharkiv) using the hot stamping. Inside this check valve is placed a solid ball made of special rubber having a certain density, which makes it possible to achieve precise operation of the valve. The valve manufactured by STA is non-separable (the thread of the body is fixed with a special anaerobic adhesive) - this is not necessary, because its design is designed for a long period of operation.
Check valves for industrial applications are special devices designed to work on pipelines with diameters of 50 mm or more. As a rule, they are made of cast iron (and for the food and chemical industry - from stainless steel) and have a flange or inter-flange mounting option. Here are some examples of such check valves:
- Check valve rotary interflange RU 16 19ch21br 1-disc cast iron
- Flanged check valve 16kch9p Du 50mm cast iron
- Check valve wafer 2-leaf RU 16 cast iron
- Flapper check valve interflange 50mm RU 16 cast iron