API Plan 11

Seal flush is taken from the pump discharge through an orifice. The function of orifice is to regulate the flow rate of flushing fluid to the seal chamber. In this plan use an orifice with a minimum 3 mm diameter based on the calculate flow rates to size orifice to adequate seal chamber flow. The flush fluid is injected directly over the seal faces with piping at 12 O clock position. In multistage pumps we get the flushing from the most convenient pump area.

API Flushing Plan 11


  • Flushing fluid taken from the discharge, hence increase seal chamber pressure and allow the fluid with less vapour margin


  • Used for clean fluid
  • Typical failure mode is a clogged orifice – check temperatures at pipe ends

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