Plant and Equipment: Flow Equipment: Valves

Valves are employed to regulate flow and pressure drop in product and service fluid lines in dairy plants. Some valves have a simple open/closed mode of operation, while others can regulate flow between these two extremes. A variety of construction principles are possible to achieve the desired mode of operation. The most important feature of any valve is the relationship between the flow rate through it and the corresponding pressure drop across it. This feature must be considered for the valve itself (the inherent characteristic) and for the valve as a component of the total flow line (the installed characteristic). Equations from fluid mechanics are available to predict this depending on the nature of the flow: compressible versus incompressible, laminar versus turbulent, and so on. One particular aspect of good valve fluid flow design is the avoidance of the phenomenon of water hammer, which, if it occurs, can damage the valve and connected pipework. Hygienic design is also essential for valves in the dairy industry, and a variety of industry and regulatory bodies can supply sound guidelines in this regard. There are a number of means to actuate a valve: manually, electrically, pneumatically, or hydraulically; however, the pneumatic option is favored by dairy processors.