Dear All,
Knowing that API 610 advises margins when designing new pumping system and accounting for potential increase in centrifugal pump speed or potential upgrade in impeller, section 6.1.4 specifies 5% margin for the same when estimating pump's head increase over the rated conditions. On the other hand, MAWP section 6.3.5 states the criteria for determining the minimum pump MAWP based on maximum discharge pressure + 10% of the maximum differential pressure also accounting for increase in speed, impeller diameter or testing tolerances. With regards to testing tolerances, table 16 of API 610 also specifies 5-10% depending on the rated pump head.
Considering an existing pump where MAWP is to be checked for revised conditions of increased differential head and increased suction pressure, If it was found that MAWP of pump casing would be exceeded under shut off conditions scenarios, can someone take credit of either one or a combination of the following:
- If pump previous performance test recorded positive tolerences in comparison to table 16 of PAI 610 with respect to shut off pressure and pump passed the performance test.
- If the pump was tested in accordance with section 8.3.2 to 1.5 * MAWP, is it acceptable to consider overpressure excursions over the casing design pressure as temporary occurrences (see API 610 section 6.3.2). I think that MAWP itself changes over the lifetime of the pump and without proper retesting, one cant have the confidence of accepting the excursions.
Appreciate your views.
Regards,
Knowing that API 610 advises margins when designing new pumping system and accounting for potential increase in centrifugal pump speed or potential upgrade in impeller, section 6.1.4 specifies 5% margin for the same when estimating pump's head increase over the rated conditions. On the other hand, MAWP section 6.3.5 states the criteria for determining the minimum pump MAWP based on maximum discharge pressure + 10% of the maximum differential pressure also accounting for increase in speed, impeller diameter or testing tolerances. With regards to testing tolerances, table 16 of API 610 also specifies 5-10% depending on the rated pump head.
Considering an existing pump where MAWP is to be checked for revised conditions of increased differential head and increased suction pressure, If it was found that MAWP of pump casing would be exceeded under shut off conditions scenarios, can someone take credit of either one or a combination of the following:
- If pump previous performance test recorded positive tolerences in comparison to table 16 of PAI 610 with respect to shut off pressure and pump passed the performance test.
- If the pump was tested in accordance with section 8.3.2 to 1.5 * MAWP, is it acceptable to consider overpressure excursions over the casing design pressure as temporary occurrences (see API 610 section 6.3.2). I think that MAWP itself changes over the lifetime of the pump and without proper retesting, one cant have the confidence of accepting the excursions.
Appreciate your views.
Regards,
