Clean-In-Place Velocity Requirements
Standard CIP requirements are to achieve 5 ft/sec of fluid velocity during the cleaning process to assure good flushing and rinsing. Sanitary processes are typically designed such that several serial components are rinsed at a time; for example, a pump, filter, transfer line, and several valves might all be part of a cleaning loop. If 2” (DN50) tubing is used, for example, then a CIP cleaning and rinsing flow rate of nearly 50 GPM is required. For many dosing, blending, and injection processes, the pumps and valves are sized too small to achieve the required pipe velocity. Typical dosing valves control well within a 20:1 or 30:1 flow rate range, making it difficult for process engineers to specify such components for both minimum dosing flow rates and maximum CIP flow rates.
CIP ByPass Valves
One typical solution is to install a CIP bypass valve around the dosing valve. Some of these bypass valves are capable of holding minimum pressure drops during the CIP process (they are effectively an engagable pressure relief valve). In other applications, such as depicted in the schematic below, diaphragm block valves are used to open up and engage a pressure relief valve or back pressure regulator. Each of these solutions adds additional complexity and testing requirements to the process design. In some cases this solution may leave small sections of the tubing without the benefit of the required flushing velocities.
Alternative Solution: Very Wide Range Metering Valve
The Equilibar flow control valve functions in a unique way compared to other sanitary metering valves. Instead of using a globe-style valve seat with limited flow range, it uses a direct sealing diaphragm and 1:1 dome air loading to modulate the flow rate. The interaction of the flexible diaphragm and the dozens of parallel orifices allows for a 1000:1 flow rate turn-down ratio. This exceptionally broad flow range allows the process engineer to specify a single valve to control dosing and blending flow rates while also opening up during the Clean-In-Place process to facilitate robust process flushing.
Learn more about how the Equilibar dosing control valve works.
Contact an Equilibar engineer to discuss your flow control application in more detail.
NOTE: This sanitary flow control valve is an adaptation of Equilibar’s established back pressure regulator product line. It is not right for every application. It has has three primary requirements: a) a flow sensor must be present in the dosing system, b) a closed loop PID loop is required to pilot the valve, and c) the upstream process pressure must be relatively stable.
Control Valve with Wide Flow Rate Range