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Wafer or butterfly valves: characteristics and materials


The components and characteristics of the wafer valves produced by Intertubi

07 September 2021
Butterfly valves are valves characterized by a disc shutter that rotates around an axis perpendicular to that of the pipe on which they are installed and act. They are used in many aspects:
- Aqueducts: they are used for interception by exploiting the main characteristics of this type of valve. In fact, being small in size, they make it possible to reduce overall dimensions compared to the classic gate valves that are normally used in this field.;
- Positive ignition engines: it is used both in the carburetor to regulate the air flow and in the injection unit to regulate the flow rate of the mixture. However, they have the disadvantage of generating significant pressure drop and other systems are sometimes preferred.
Wafer valves are a particular configuration of butterfly valves with four centering ears obtained by casting the valve body.

The components of the wafer valves

Wafer valves have a number of components required for proper operation:
- Valve body: represents the bulkier part and the support of the whole component. Usually made of spheroidal cast iron, carbon steel or stainless steel exploiting both the resistance characteristics and the corrosion resistance.
- Seat: made of elastomeric material and is necessary for sealing to avoid pressure or flow losses.
- Disc: it is the rotating element that acts as a shutter when the valve is closed and is also made of the same materials as the valve body.
These are the main components of the valve but there are also an underlying flange and the shaft that are made of the same materials as the disc and the valve body. It is important to note that corrosion resistance is the main requirement and various methods are used for protection such as paints based on epoxy powders. All materials must have organoleptic, chemical, physical and biological characteristics such as to comply with health regulations because they come into contact with fluids for human consumption.

The characteristics of wafer valves

Wafer valves are valves which, as seen, act by rotating the disc. Intermediate positions, however, generate pressure drops and inefficiencies and, for this reason, it is preferred not to use them for flow regulation but only in the two main configurations. Usually a clockwise closing is chosen for design reasons but there may also be an anticlockwise closing if appropriately specified on the supply.
Numerous construction possibilities can be envisaged for the closure:
- Manual: if the diameter is small, a handwheel or lever can be used to force the closure;
- Demultipliers: with larger diameters or important pressures, it is necessary to use devices;
- Bypass: used to force closure by programming the pressure that is established on the two different faces of the closure disc.

Regulations and markings of wafer valves

Wafer valves, to be introduced on the market, must comply with some important certifications:
- UNI EN 10204 3.1: it is a type of certification that certifies that the manufacturer has made the product according to the customer's specifications. In fact, this certificate summarizes the characteristics of the materials used, the results of tests carried out by a department independent of the factory, heat treatments and other properties.
- UNI EN 12266-1: it concerns the specifications and characteristics of the pressure tests, as well as the acceptance criteria of the same.
- UNI EN 1074-1, 1074-2: establishes the criteria to be followed in the design, testing and installation of components that transport water intended for human use.
Compliance with these standards is a fundamental requirement for the certification of the product and, in this specific case, of important components such as wafer or butterfly valves.

The marking of the wafer valves

The marking, that is the identification code of each individual product, must have some standard characteristics for wafer valves: in fact, the nominal diameter, the nominal pressure, the material of the valve body, the name of the manufacturer and the year of production must be present (not the year of implementation) and, finally, the reference regulations which are those described above. This code allows you to uniquely identify each component in the event of damage or breakdowns, speeding up troubleshooting operations.

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