Duplex pump performance

The charts showing the p>erformance of duplex pumps are shown in Table 4-38 [17]. The charts showing the performance of triplex pumps are shown in Table 4-39 [17]. A chart listing the pump output required for a given annular velocity is shown in Table 4-40 [18]. A chart listing the power input horsepower required for a given pump working pressure is shown in Table 4-41 [19]. 

The use of stainless steel in oil production has increased, and is of particular significance for production in deep waters. This applies both to production and process equipment carrying oil and gas and to seawater systems. For seawater systems the experience from nuclear power plants has been useful. In these plants, some high-alloy steels have performed well in equipments such as seawater pumps and heat exchangers. But the performance depends on service conditions, design and combination of materials. On the oil/gas side, good experience has been obtained with 13% Cr steel in production tubing, in components at the wellhead and in well valves. The same can be said about the use of other stainless steels in process systems offshore, but there have been some exceptions. For instance, SCC has occurred on duplex steel (22-5-3) under external heat insulation (compare Section 7.12) [10.11]. 

Cracks have been discovered in cast primary pump bodies, valves and elbows in main circulation loops. Dye penetrant testing revealed a number of cracks. The cracks were found both on the inside and on the outside of the casings. Moreover, the duplex austenitic-ferritic structure of cast steel pipes used in some NPPs is a potential cause of an embrittlement due to the thermal ageing effect on the ferritic part. It is difficult to perform reliable volumetric non-destructive testing by ultrasonic techniques of the cast material. 

Materials for FGD pumps with suspension temperatures up to 70 °C are subjected to extreme corrosive conditions. To discover whether duplex steels can withstand these conditions, corrosion tests were performed on two types of alloy - standard alloy 1.4517 (sample No. 5,5.1,21,28), with slight variations in Cr, Mo, Cu, and N content, and the material 1.4471 (G-X3CrNiMoCuWN26-6-3-1-1, sample 12 and 23), a 1% W alloyed cast duplex stainless steel. The good corrosion resistance of this duplex stainless steel is illustrated in Fig. 1-49. In a fluoride-free medium, the critical breakthrough potential is 940 mVscE. With increasing fluoride content, it decreases to ca 200 mV, but with a value of 720 mVscE for a fluoride content of 500 mg L the resistance is quite high. 

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