The Logic Behind The Magic."Produce water Hydrocyclones"

The purpose of the Produced water treatment is to de-oil the produced water before injection back to reservoir. Produced water treatment is designed to achieve the discharge oil-in water to meet the specification (e.g. 25 mg/L (ppmV). A common oil in water analyzer is usually installed for monitoring and recording of oil content in water from Produced oil water treater vessels
Under normal operating condition, produced water from the MP separators flows into hydrocyclones and the produced water flow is regulated by the interface level controller in the Separators. 

The hydrocyclone is operated under differential pressure ratio controller i.e the ratio of  (hydrocyclone inlet pressure minus reject oil stream pressure) to ( hydrocyclone inlet pressure minus hydrocyclone water outler pressure).  The DPR controller is set at adjusted value and will continuously adjust the hydrocyclone reject oil control valves to achieve the DPR set point.

 Control loop description.

The amount of oil recovered through the hydrocyclone is determined by the differential pressure ratio of (inlet pressure minus oil stream pressure) over (inlet pressure minus water outlet  pressure).
the output is calculated using the folloeing formula:
Ratio = (P inlet hydrocyclone - P oil reject stream pressure) / (P water outlet hydrocyclone - P oil reject stream pressure).

The PDIC will maintain the differential pressure ratio at set point (i.e 1.7) by regulating the pressure control valve PDV at reject oil stream.  The control valve is fail closed type. THe PDIC controller output signal shall be reverse acting and the control valve is direct. As the differential ratio falls bellow setpoint, the controller shall open the pressure control valve to increase the differential pressure ratio. High and Low alarm shall be displayed on the HMI.