A flume not larger than how many feet emitting from the safety exhaust port is the maximum permissible boiler safety valve leakage?

The correct answer reflects that a flume from the safety exhaust port should not exceed a specific size in feet, which is crucial for maintaining safe operational standards in a boiler system. When a safety valve leaks, the leakage can create steam or vapor that must be effectively directed away from the vicinity of the boiler to prevent hazards such as scalding or excessive pressure buildup.

In this context, a flume not larger than three feet indicates that any leakage should be contained and controlled, minimizing risks associated with escaping steam. This precaution helps ensure that the system operates safely and within established guidelines. The specified limit allows for proper function of the safety mechanisms while preventing potentially dangerous situations.

Understanding this aspect of boiler safety management highlights the importance of adhering to specifications regarding safety valve performance, which is foundational for safe operations in a machinist's environment. The other options, which suggest larger flume sizes, would not adhere to the strict safety practices necessary for effective boiler management, leading to higher risks of accidents or operational failures.