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Water quality
Water quality
There is a requirement in API 610 for Centrifugal Pumps (Cl. no. 7.3.2.3) that the water quality to be used for Hydrostatic testing pumps with austenitic stainless steel materials shall not exceed 50 ppm w. Can anybody please clarify why this water quality requirement is not applicable for water to be used during the performance testing of the pumps?
In one of of the projects we are executing the hydro test is to be performed for 4 hrs and the combined performance and mechanical run test is scheduled for 6 hrs total. This way I suppose the performance test is to be regarded as more severe?
"Hydrostatic testing of austenitic stainless steel vessels shall be done with potable quality water having a chloride content less than 50 ppm shall be used for hydro testing." is the way it is normally written.
Austenitic stainless steels are subject to stress cracking corrosion typically when the chloride concentration is over 200 mg/l for the entire service life. The service life is in terms of year.
Specifying the chloride content for a 4-hour test period is very conservative because the austenitic stainless steel will not be attacked in such a short time period.
Use of "potable water" is more appropriate as a standard for testing water. Most potable waters actually have a chloride content less than 200 mg/l.
Probably the reason that this is specified is that the pump manufacturers are probably not that familiar with the details of water quality.
Austenitic stainless steels are subject to stress cracking corrosion typically when the chloride concentration is over 200 mg/l for the entire service life. The service life is in terms of year.
Specifying the chloride content for a 4-hour test period is very conservative because the austenitic stainless steel will not be attacked in such a short time period.
Use of "potable water" is more appropriate as a standard for testing water. Most potable waters actually have a chloride content less than 200 mg/l.
Probably the reason that this is specified is that the pump manufacturers are probably not that familiar with the details of water quality.
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2011-06-06
