Butterfly valves - Nocado - #4

Technical Information

Due to the special geometry of the chamber where the sealing is installed complete vacuum stability is guaranteed for valves up to DN 100.

• For the allowable pressures, it is necessary to know

othe differential pressure against which the

valve closes o the allowable system pressure. The required system pressure can be quite high particularly on heated systems and for carbonated beverages. Butterfly valves up to DN 65 of the nocanorm line are laid out for 16 bars; valves for higher pressures are avail­able in the nocaplus line.

(see also: General planning infomation)

• If the flow rates are too low, any solids can settle down in the line and impair the func­tion of the butterfly valve.

• When a butterfly valve is closed quickly, the flow separation causes a vacuum on the flap and in the area of the butterfly valve gasket. At flow rates of approx. 3.5 m/s, the valve should be closed only at significantly re­duced speed to reduce pressure impacts and prevent a damage of the valve.

Stainless steel

• Stainless steel in the qualities AISI 304/304 L is resistant to most food and luxuries and the cleaning agents used in this context.

• Corrosion is seldom the result of incorrect material selection, but rather usually caused by processing errors.

• In the case of high percentages of halo­genides (e.g. chloride), especially at increased temperatures or at high acid concentra­tions, higher-quality stainless steel or other materials should be used.

Gaskets

• The sealing quality has a decisive influence on the service life of a gasket. In addition to the geometry the mixture and production process are decisive for the function and service life. In spite of the same chemical designations, gaskets differ on the basis of the additives and particularly, the degree of cross-linkage.

Exceptionally high product temperatures can also destroy the structure of the gasket. Gaskets may be defective even though they appear to be intact.

o The usual temperature specifications are based on dry air and are therefore not transferable to practical applications. o The allowable temperatures for liquid or

steam are considerably lower in general. In addition to the resistance to temperature and corrosion, the swelling characteristics of gaskets are decisive for their suitability. Due to improvements on the geometry of the gaskets and the installation space, which are applied for a patent, a considerably higher resistance will be obtained against negative influences such as expansion due to temperature and swelling characteristics. The following information is required for the selection of gaskets. o Product (also CIP/SIP) in contact with gas­ket, including

* duration of contact

* concentration

* temperature or temperature change

* switching cycles

An abundance of analysis procedures are available for the gasket qualities, but there