Curtiss-Wright Inc.

Abstract This article presents the benefits and challenges of modern aircraft structural design. It explains the structural analysis methods used for the establishment of allowables. The article describes the development of laser peening parameters, and the implementation of laser peening. It provides a detailed discussion of qualification testing. The article also presents an overview of digital tools for process implementation.

Lead-containing additives have long been incorporated into molybdenum disulphide (MoS2) solid lubricants to improve tribological performance; however, increasing environmental and health concerns have created a need for sustainable alternatives. In this study, silver oxide (Ag2O) was investigated as an environmentally friendly replacement for lead phosphite in the commercial bonded MoS2–Sb2O3-lead phosphite solid lubricant (Kal-Gard FA). A newly developed lead-free coating (MoS2–Sb2O3–Ag2O) was compared tribologically with the baseline (Kal-Gard FA) using reciprocating ball-on-flat sliding tests against an alumina ball under ambient conditions. The developed MoS2–Sb2O3–Ag2O coating was further examined under normal loads ranging from 1 to 10 N to assess its load-bearing capacity. Both coatings exhibited comparable steady-state friction coefficients ( 0.18–0.19) at 1 N despite differences in running-in behavior, with the MoS2–Sb2O3–Ag2O coating requiring a longer running-in period. FESEM/EDS, FIB, and Raman analyses revealed that both formulations developed MoS2-rich tribofilm and transfer film layers that likely governed the friction behavior. However, the wear rate of the MoS2–Sb2O3–Ag2O coating was approximately twice that of the baseline, indicating that wear performance was more sensitive to additive substitution than friction. FIB analyses revealed that the Ag2O-containing coating developed a thinner tribofilm than the baseline coating, which likely contributed to its higher wear rate. Increasing the normal load from 1 to 8 N reduced both the running-in duration and the steady-state friction coefficient of MoS2–Sb2O3–Ag2O coating owing to improved shear accommodation within the MoS2-rich tribological interface. However, at 10 N, tribofilm breakdown, substrate exposure, and unstable friction behavior were observed. Overall, the results demonstrate that Ag2O can successfully replace lead phosphite while maintaining comparable friction performance, although further optimization is required to achieve wear resistance comparable to that of the lead-containing baseline.

Thrust bearings have historically been designed with relatively thick (rigid) shoes to minimize structural deformations under the hydrodynamic pressures developed in the lubricant film. This is necessary when the shoes are supported near their geometric centers, as excessive convex crowning would ensue if the shoes were not sufficiently rigid to resist the hydrodynamic pressures tending to distort the shoes into a convex shape. However, a rigid shoe can also compromise hydrodynamic pressure development if thermal distortions or manufacturing discrepancies cause the crown to become excessively concave or convex. In this case, a structurally rigid shoe can overwhelm the hydrodynamic pressures and lead to loss of film and bearing failure. This is especially true of water-lubricated bearings, whose operating film thicknesses are typically 50% to 80% lower than those of their oil-lubricated counterparts, enabling shoe distortions to more easily rival film thicknesses. The current study reveals how thrust bearing shoes with embedded flexibility can conform (self-adapt) under the various hydrodynamic pressure distributions occurring in the film. The result is a shoe that can self-adapt to counteract manufacturing discrepancies or distortions from changing thermal conditions.

This paper will present the general design features and associated testing to validate a 1750 HP canned motor pump (CMP) as an alternative to traditional electric submersible pumps (ESP) for the production of oil and gas in subsea caisson applications where reliability is essential. The CMP development aimed at designing a robust solution that eliminates typical failure points of submersible pumps and validating the design to demonstrate its readiness for deployment. The CMP is a seal-less topology that has been employed in other critical applications including radioactive slurry and commercial nuclear applications. This fit for purpose caisson CMP was engineered and manufactured to meet the operating conditions for a specified offshore application. The CMP development included mockups to validate materials, design features, manufacturing processes, and performance. The full CMP system testing was performed in water at the vendor's test facility and with 2 to 300cP viscosity, multiphase fluids at the end user's test facility. CMP validation was achieved via evaluation of the test results and post-test inspections on key components, including bearings. Typical caisson ESPs have a run life of approximately 2.5 years. Root cause failure analyses (RCFA) on these systems have shown a majority of failures resulting from the seal and motor. The main function of the seal section is to protect the motor from contamination by the process fluid. Once the seal section is compromised, the motor becomes susceptible to failure modes due to degradation of dielectric fluid. The seal-less CMP system eliminates need for a mechanical seal or seal section by isolating the wound stator from the process fluid with a corrosion resistant liner. An outcome of this configuration is that all bearings must operate in the process fluid. Presented data will include results from thrust bearing testing in multiphase fluid to demonstrate robustness in wide varying conditions in addition to performance testing from the full CMP system testing in water and multiphase fluids. Post-test inspection results of key components will be presented to support the conclusion that the CMP system is ready for deployment. The canned motor pump (CMP) for caisson applications is a non-conventional alternative to typical ESPs through the elimination of the seal section and use of process lubricated bearings. This paper will share features, learnings, and results that demonstrate the canned motor pump technology is ready for deployment in a subsea ESP caisson application.

The objective of this paper is to demonstrate the successful qualification of a 3.0MW canned motor pump for subsea seawater applications via wet-pit testing. The canned motor topology ensures high reliability by eliminating the need for a barrier fluid system and mechanical seal. This topology uses the process fluid as the lone lubricant and cooling media in the motor resulting in an all-electric seabed barrier fluid-less pumping system for the subsea injection of treated seawater into a reservoir. To qualify canned motor technology for deployment subsea, a full-scale, 3.0MW canned motor water injection pump was tested in a wet-pit to demonstrate a Technology Readiness Level (TRL) of 4 per API 17Q. Pump performance was characterized across the entire operating speed range with a suite of instrumentation, recording parameters including flow, differential pressure, casing and rotor vibration, winding temperatures, and electrical parameters. The test program encompassed operation across a wide spectrum of envisioned conditions including over-speed conditions, cyclic testing, emergency shutdown conditions, and endurance testing at full load. Qualification was achieved via evaluation of the test results and post-test inspection of key components, including bearings. Canned motor pumps have a demonstrated track record for more than 50 years in various critical applications. This development and qualification program demonstrates how this technology has been adapted to serve as a subsea barrier fluid-less motor-pump system and its potential to optimize field economics through an all-electric power distribution system. The paper will demonstrate qualification unit performance and reliability under simulated operating conditions and transients. Presented data will show performance meets predictions, how the unit showed no observed change over time during replicated lifetime of service cycles, and endurance testing results. Inspection results, to be shared, showed all major components in good working conditions and that the bearings demonstrated no indications of rubbing or contact. These results support qualification to a Technology Readiness Level (TRL) of 4 per API 17Q, which has been endorsed by several end users who followed testing and reviewed the data. The implementation of a canned motor pump to this subsea application results in a non-conventional, barrier fluid-less pumping system creates the potential to optimize field economics. Elimination of the mechanical seal and barrier fluid increases reliability and prevents process water contamination. This topology also enables economic saving through removing the need for topside hydraulic power units (HPU), hydraulic lines in an umbilical, and enabling an all-electric subsea architecture including permitting longer step-outs. The canned motor topology is scalable and flexible, with demonstrated reliable operation in topside applications up to 5.5 MW, and utilized in pumping applications with multiphase fluids and highly abrasive solids.