Parametric series of canned electric pumps

Abstract

Pumps with mechanical shaft seals are used for most applications in petroleum refineries involving explosive, flammable, or toxic liquids and liquefied gases. Experience in the operation of such pumps has demonstrated that mechanical seals, even those of high quality, cannot guarantee absolutely tight sealing. As the seals wear down, the fluid leakage increases; this is particularly true for liquefied gases. An analysis of the existing systems of mechanical seals shows that during their normal life, it is practically impossible to prevent leakage. Therefore, in pumping toxic or ecologically hazardous media, in particular liquefied gases, it is necessary to employ glandless pumps, i.e., canned pumps. On the basis of the requirements of NORSI, a parametric series of canned pumps has been systematized for production operations that now exist or will be started up in the future (see Table 1). All of the pumps in this series were developed by the Experimental Design Bureau of Machinery Construction (OKBM) of the Ministry of Atomic Energy of the Russian Federation, on the basis of canned electric pumps they had developed previously for shipboard atomic power units. The total service time accumulated by these pumps in ship reactor units was more than 15,000 years. The maximum operating time was accumulated in the atomic icebreaker Arktika in 22 years of operation without shutdowns or repairs: more than 120,000 h (10 pumps). In designing this series, use was made of basic technical solutions and know-how in the design of pumps for shipboard units to give them a high level of service qualities: vertical position; complete unloading of radial and support bearings by the action of hydraulic forces; specially designed bearings; silicided graphite as an antifriction material; seamless Nichrome protective sleeve of stator, welded to housing; external composite-welded housing of stator with sealed-in metal-ceramic electrical leads, preventing any penetration of the pumped liquid to the atmosphere, even with accidental damage of the protective sleeve of the stator. Of this series, NORSI is operating three GleN 70/65 canned electric pumps handling phenol. The first of these has operated for 28,150 h since 1981, the second 12,000 h since 1993, and the third 2000 h since 1994. Operation without maintenance or reworking will be continued up to the design operating life, 40,000 h. At that time; on the basis of inspection results, it will be decided whether to continue" the pumps in service.