MATERIAL DURABILITY IN WATER HAMMER SYSTEMS: STRENGTH, WEAR, AND SERVICE LIFE OF THE GIF² IMPULSE FLOW FORMER

Abstract

The article presents a comprehensive materials science substantiation for the selection of structural materials for all main components of the Gravitational-Impulse Flow Former (GIF²) system [1–3]. The system operates under an extreme cyclic regime: pressure amplitude up to 15.2 MPa (150 atm), nominal impulse frequency of 2.39 Hz, local flow velocity up to 126 m/s, instantaneous flow rate up to 338 L/s [3]. Based on an analysis of the operating conditions and detailed design documentation [4–9], engineering calculations of strength, fatigue life [14, 15, 17], wear resistance [18–21], and service life were performed for 20 main system components (according to AISI and GOST/DSTU standards): the tank with a load-bearing secondary bottom (AISI 316) [4], pipelines and angle elbows (AISI 316) [4, 29], swing check valves (AISI 4340, AISI 9310, ceramic bearings (SiC, CeramicSpeed type) [5], two-stage spring pressure absorbers (AISI 4340, titanium VT6, 50KhFA) [6], Laval nozzle (40KhN2MA) [7], hydraulic seal (AISI 304) [8], accumulator-stabilizer (AISI 4340, reinforced polymer (PTFE) [2, 24, 25], and the nozzle assembly (Inconel 718) [9, 23]. A separate section is devoted to the engineering substantiation of the operability of swing check valves under cyclic water hammer conditions of 150 atm with a frequency of 2.39 Hz [5, 10–13, 17, 19, 20]. The calculation results confirm the achievement of the design service life of at least 15 years of continuous round‑the‑clock operation for all system components, except for the accumulator membrane, which is a replaceable element and requires periodic replacement [2, 24, 25]. The energy substantiation of the system's operability, including the energy concentration coefficient (KEP = 574) and conversion efficiency (η = 66.1%), is presented in [3].