Change over valves
A change over valve is a device used for redirecting the flow from one pipe to another. Perhaps the most typical change over valve application is related to two safety valves, where duplicated valves are connected to the inlet and outlet pipe by change over valves connected together. In such cases, one of the safety valves can be kept in operation and the other serviced if required by turning a single hand wheel.
Change over valves can be implemented in many different ways. A seat-type change over valve can be used with a closing element in the middle of the Y-shaped body, with seals on both of its sides. The valve closes against one of the seals, while the other one is fully open. Such change over valves are manufactured by ARI, FEMA, and DESCOTE, for example. The DESCOTE change over valve is also available in a version with bellows.
Another way for change over valve implementation is to use a three-way plug valve. This allows utilisation of the advantages of plug valves. For example, in the case of problematic chemicals, a lined three-way plug valve can be used. The AZ range includes a change over valve system with two three-way plug valves connected to the same drive.