Below are the reasons as to why an AVK valve should be chosen -
The Rubber Absorbs Impurities
A correct rubber compound is soft enough to absorb impurities, yet strong enough to wash the impurities through when the valve is opened again. This means that the rubber surface will regain its original shape securing a drop-tight sealing. Tests prove that the rubber surface of a DN 250 wedge absorbs impurities up to Ø8.7 mm.
Safe Operation and Long Durability
A fixed wedge nut reduces the number of moveable parts and prevents vibration, thus preventing corrosion, malfunction and water hammer. The wedge nut is made of dezincification resistant brass with lubricating abilities which provides optimum compatibility with the stainless-steel stem. It is sealed at the top and bottom with rubber to prevent corrosion.
High Quality Rubber Compounds
The ductile iron core is fully vulcanized with rubber both inside and outside. A minimum of 1.5 mm rubber is applied on all pressure bearing surfaces and a minimum of 4 mm on all sealing surfaces, regardless of the design.
A unique vulcanization process ensures that the entire wedge core is covered with rubber and that the shoes are attached to the wedge core. This process is one of the secrets to keeping the wedge protected from corrosion and thus securing long life and smooth operation of the valve.
Double Bonding Secures Excellent Rubber Adhesion
The wedge core is immersed in two different baths. The first is implemented to prepare the ductile iron core and the second is to vulcanize the rubber to the core. Since no international bonding standard is available, AVK has developed its own harsh test method to ensure that the adhesion also withstands extremely intense situations. Testing is done both during production and after immersion in 90°C water for 3 weeks. When peeling off rubber from the core, the core must still be covered with rubber.
Compression Set Ability to Regain Original Shape
The rubber is deformed by 25% of its original thickness at a constant temperature for a specific time. The pressure on the rubber is relieved and the layer thickness is measured after half an hour. The smaller the deformation, the better the memory effect. EN 681-1 states that these are the minimum requirements for the compression set value. The smaller the permanent deformation, the better the compression set.
Resistance to Water Treatment Chemicals
The rubber, which is a complex formulation of many ingredients, is developed and tested by AVK’s own R&D scientists. AVK has the most advanced state of the art mixing facility which ensures repeatability and high performance materials. Tests are continuously carried out to ensure that the correct rubber compound is applied for the right area of use. The rubber compounds are also ozone tested.
Avoid Contamination, Minimize Formation of Biofilm
AVK’s EPDM rubber recipes are composed with focus on minimizing the formation of biofilm. As a result, the rubber will not provide a breeding ground for bacteria.
Drinking Water Approvals
All rubber compounds are approved according to international standards such as WRAS and NSF-61.