AMP_04_May_June_2021_Digital_Edition

A D V A N C E D M A T E R I A L S & P R O C E S S E S | M A Y / J U N E 2 0 2 1 2 8 THE PACT BETWEEN PRESERVATION AND RUIN As the engineering systems of the world adapt and change due to the effects of the pandemic on global health and worldwide economies, engineers and scientists provide paths of preservation to ensure safe and reliable operations. Daniel B. Denis,* Structural Integrity Associates Inc., Simsbury, Connecticut MATERIALS SCIENCE AND CORONAVIRUS SERIES T he COVID-19 pandemic has changed many things about busi- ness adaptation and engineer- ing performance. Beginning more than a year ago, people moved to remote operations and in-person workforces were reduced to minimal levels, to keep safe separation and distance. Produc- tion lines were reorganized to prioritize health and safety, and costs were cut for businesses to weather the current storm. Some operations are beginning to ramp back up as procedures and pre- cautions continue to be implemented. But a surprising and unexpected result of the pandemic has been a shift in the way that products and equip- ment have been utilized, as a result of changes in people’s behavioral pat- terns. These include actions such as shifts in travel frequency, commuting routines, electricity usage, and use of public facilities. AVIATION TRAVEL REDUCTION Both personal and business trav- el worldwide has greatly diminished since the beginning of the COVID-19 pandemic. The reduction in air traf- fic greatly lowered engine use in com- mercial aircraft, which were designed for consistent utilization. When an air- plane lands at an airport, the plane is rapidly prepared for a near-term de- parture, as time on ground is potential unrealized revenue for airlines. During flight, higher temperature and pres- sure (than idle ground conditions) is ex- erted on the engine, exposing the parts and systems to the design environment and conditions. These parameters are *Member of ASM International generally predictable and expected, and those conditions are included in the initial choices for consideration for how a system is designed. Specific ma- terials and processing chosen for parts and systems satisfied the functional constraints. Similar to a snowblower or lawn- mower that sits idle during the summer or winter seasons, respectively, certain techniques must be employed to en- sure that the engine is appropriately preserved during periods of extended downtime. In these household devic- es, the stagnant gasoline can turn to a gel-like substance, preventing prop- er startup and ignition of the engine. Fuel stabilizer agents must be added to preserve the fuel to ensure that these devices can successfully operate as needed. Often, a periodic engine restart confirms operational capability. In aviation, the pandemic result- ed in reduction in demand, so airplanes were grounded for extended periods of time. The most efficient engines (in terms of fuel burn) were kept flying to capacity. But lower efficiency engines were flown less frequently or not at all. Because these grounded planes were not designed for extended periods of non-use, there has been potential for these shutdown scenarios to go beyond original design basis considerations. Even if the situation is within analyzed design considerations, the lack of op- erational experience with these condi- tions may change the confidence for an end-user to appropriately understand and address these situations. POWER PLANT PIPING In fossil and nuclear power plants, normal operation (when electricity is produced) through heat generation is the typical condition under which sys- tems are designed and analyzed. The pressures and temperatures that are limiting constraints are applied, along with transients and various potential accident conditions. The shutdown windows for maintenance are generally minimized as much as possible for both economic and safety reasons, but when these conditions are extended beyond usual time limits, adverse conditions can occur. In piping systems, fluid is expect- ed to normally travel through the sys- tem. Because of this movement of the fluidmedia, contaminants and particles are distributed, filtered, or managed. In extended shutdown conditions, these consistent flows are not present, and effects can occur that present risk to the overall system. For corrosion, the normal flush- ing of surfaces from contaminants is important to minimize the potential for stock loss or other corrosion mech- anisms. In shutdown scenarios, cool- ant or fluid is not rapidly flowing, which can allow for stagnant concentration of contaminants (Fig. 1). Additionally, contaminants can concentrate on the outside surface of equipment or pip- ing through the combination of me- dia exposure and evaporation. These scenarios can modify and greatly affect the thermodynamics and kinet- ics of an applied degradation mechan-