Shutoff pressure = MAX HEAD @ RATED IMPELLER

Very important Point: note that maximum head in stable curve is occurred at shutoff pressure but when curve is not stable and is unstable, max curve is occurred another region, often near to shutoff pressure.

• The pump head at shutoff not exceed 120% of the head at the rated capacity point. In addition, it is required that pumps be capable of at least a 5% head increase at rated conditions by impeller replacement.
• If head rise to shutoff in excess of the 120% rated flow, process shall confirm check design pressures of downstream equipment must be evaluated and revised as necessary.
• Centrifugal pump require that the pump head capacity characteristic curve rise continuously from the rated flow to shutoff (no flow delivered)
• 1.11 Pumps that have stable head/flowrate curves (continuous head rise to shutoff) are preferred for all applications and are required if parallel operation is specified. If parallel operation is specified, the head rise from rated point to shutoff shall be at least 10 %. If a discharge orifice is used as a means of providing a continuous rise to shutoff, this use shall be stated in the proposal. {API 610}

Comments:

• The pump head at shutoff shall not exceed 120% of the head at the rated capacity point.
• It is required that pumps be capable of at least a 5% head increase at rated conditions by impeller replacement.
• Centrifugal pump require that the pump head capacity characteristic curve rise continuously from the rated flow to shutoff (no flow delivered)
• If parallel operation is specified, the head rise from rated point to shutoff shall be at least 10 %. {API 610}
• If a discharge orifice is used as a means of providing a continuous rise to shutoff, this use shall be stated in the proposal. {API 610}