方案五

　　What

　　Recirculation from seal chamber to pump suction through

　　orifice .

　　Standard flush plan on vertical pumps .

　　Why

　　Continuous seal chamber venting on vertical pumps .

　　Seal chamber heat removal

　　Where

　　Vertical pumps .

　　Seal chamber pressure is greater than suction pressure .

　　Moderate temperature fluids with moderate solids .

　　Non-polymerizing fluids

　　Preventative Maintenance

　　Vent piping loop prior to starting vertical pumps .

　　Use an orifice with a minimum 3 mm ( 1/8inch )diameter .

　　Calculate flow rates to size orifice for adequate seal chamber

　　flow .

　　Reduce seal chamber pressure with proper orifice and throat

　　bushing sizing

　　Typical failure mode is clogged orifice check temperatures

　　at pipe ends