2010 09 Hanif FFC UreaKnowHow.com HP Carbamate Pumps Damage Failure Report
This case takes place in one of the three Saipem urea plants with a design capacity of 2105 mtpd. The high pressure carbamate solution recycle pumps, P102A/B, are two stage centrifugal pumps manufactured by Sundstrand, USA. The two stages of the pumps are mounted in a back arrangement on each end of the high speed shaft rotating at 16000 rpm. The low speed shaft driven by 630 KW motor rotates at 3000 rpm These pumps have a history of damage particularly at 2nd stage since commissioning in 1982 (09 damages at Pump A and 05 at Pump B). In April 2007, P102A 2nd stage was damaged after seal flush failure. After overhauling, the pump performed normal up till April 2010 when it again damaged after seal flush failure. A multi disciplinary Task Force analyzed the sequence of events and concluded that the pump thrust increased due to low seal flush and a process upset. This caused rubbing of the impeller and dynamic rotors with stators. The Bentley Nevada 72000 system could not cause tripping of the pump due to a possible deflection in the gear box frame and mounting arrangement of the probes. Several recommendations were made to improve the reliability of these pumps.