Final answer:
The oil temperature limits are likely set at -20°C instead of -50°C due to the operating environment, the type of oil, design requirements, and the balance between resource extraction and environmental protection as seen in cases like the Alaska Pipeline construction.
Step-by-step explanation:
The specific setting of oil temperature limits in engineering systems is contingent upon a variety of factors including the physical properties of the oil, operational safety margins, and environmental conditions. When considering why the oil temperature limits are set at -20°C instead of -50°C, it is crucial to understand the context in which these temperatures are applied. The use of a higher temperature limit might be a result of the operating environment, the type of oil used, or the specific engineering design requirements of the application.
For instance, in the case of the Alaska Pipeline mentioned above, environmental considerations played a significant role in the engineering decisions. The design took into account the unique Alaskan ecology and the need to balance both resource extraction and environmental protection. The temperature settings may therefore reflect the specific climate conditions in Alaska and the technological capabilities of that period to ensure that oil could flow efficiently without posing significant environmental risks. Similarly, the choice to not operate at even lower temperatures like -50°C may have been influenced by factors such as the increased energy required to maintain oil liquidity or the risk of technical complications at such extreme temperatures.
Nevertheless, without specific engineering documentation or standards pertaining to the AL reference, it is challenging to provide a definitive answer as to why -20°C was chosen over -50°C. Engaging with the technical specifications and historical context may yield a more precise explanation of these temperature limits.