American Society of Mechanical Engineers (ASME) Practice Exam

The correct size for the letters stamped on a boiler is 5/16 inch. This requirement is grounded in safety standards and regulations that specify the minimum height of letters to ensure legibility and clarity of critical information regarding the boiler, such as capacity and operating pressure. Legible markings help operators and inspectors quickly gather essential information, which is vital for safe operation and maintenance. While other sizes such as 1/4 inch, 1/2 inch, and 3/8 inch may seem reasonable, they do not meet the established regulatory standards aimed at maximizing visibility and reducing the risk of misunderstandings that could lead to operational errors or safety hazards. The choice of 5/16 inch strikes a balance between being sufficiently large for visibility while still being manageable in terms of space on the boiler surfaces.