ANS:B - 10

The maximum permissible air velocity in pipelines can indeed vary depending on several factors, including the specific application, industry standards, and safety considerations. While velocities of up to 20 meters/second may be acceptable in certain situations, a more conservative value commonly used for general applications is around 10 meters/second. This limit helps ensure efficient airflow while minimizing the risk of issues such as excessive pressure drop, erosion of pipeline materials, and noise generation. Additionally, higher velocities may also increase the likelihood of turbulence within the pipeline, which can negatively impact the overall performance and efficiency of the system. Therefore, a maximum air velocity of approximately 10 meters/second is often considered a safe and practical guideline for many pipeline applications. However, it's essential to consult industry standards, specific engineering guidelines, and the requirements of individual applications to determine the appropriate velocity limits for a given situation.