Method for identification of impeller wear and excessive wear-ring clearance in centrifugal pumps

A method for determining mechanical degradation of parts of a centrifugal pump having a fluid inlet, an impeller and a fluid outlet, comprising:

• calculating at least one of a wear-ring clearance effect and an impeller wear effect where:
• calculating said wear-ring clearance effect is done through:
• measuring an actual pump flow rate Op and actual pump power Pwp,
• calculating an internal flow rate of the pump QpPwp through projecting said actual pump power Pwp on a theoretical Pump Mechanical power versus Pump Flow rate curve at iso mechanical power,
• calculating the mechanical power PwQp that should be used if the pump worked as specified in the theoretical curve through projecting said actual pump flow rate on said theoretical Pump Mechanical Power versus Pump Flow rate curve at iso flow rate,
• applying the measured flow rate Op on a theoretical Pump Head versus Pump Flow rate curve to obtain a theoretical Head Hpth,
• applying the internal flow rate of the pump QpPwp on said theoretical Pump Head versus Pump Flow rate curve to obtain an internal Head HpPwp,
• calculating a difference between said theoretical Head and said internal Head Hpth−HpPwp to obtain the loss of Head due to the wear-ring clearance;
• and where:
• calculating said impeller wear effect is done through:
• measuring an actual input pressure pin, an actual output pressure pout and an actual pump power Pwp,
• calculating a theoretical flow rate QpPwp corresponding to the measured mechanical power Pwp on a theoretical pump characteristic Pump Power versus Pump Flow rate curve,
• projecting such theoretical flow rate QpPwp on a theoretical Pump Head versus Pump Flow rate curve at iso-pump flow rate ΔQ=0 to obtain a theoretical Pump Head HpPwp,
• calculating the actual Pump Head Hp from the actual input pressure pin, and the actual output pressure pout and a pumped fluid density,
• calculating a difference between said theoretical pump head and said actual pump Head HpPwp−Hp to obtain the loss of head due to the impeller wear.