Abstract: A newly constructed alkylation unit design has selected shielded pumps and centrifugal pumps as the main mechanical pumps. Among them, the shielded pumps mainly follow the API 68—2011 standard (hereinafter referred to as API 685) and the centrifugal pumps mainly follow the API 610 11th Edition standard (hereinafter referred to as API 610). By comparing the overhaul situation of the pumps during the 48-month operation period, it was found that the maintenance rate of the shielded pumps was much higher than that of the centrifugal pumps. In order to identify the causes of high maintenance rates in shielded pumps, a comparative analysis was conducted on the differences between these two types of pumps during the design and trial operation phases. The study revealed that the API 685 standard exhibit multiple deficiencies in commercial viability and manufacturing details compared to the API 610 standard. Meanwhile, shielded pumps present certain challenges during trial operations due to their unique structural characteristics, which reduce the operational reliability. Aiming at the aforementioned deficiencies and combining with the comparative advantages of centrifugal pumps, optimization direction of shielded pumps is proposed.

Key words: shielded pumplAPI 685lcentrifugal pumplAPI 610loptimization