What size generating tube stock is permitted inside the steam and mud drum of a boiler?

• A. 1 1/2 inch to 2 inch
• B. 1/4 inch to 1/2 inch
• C. 2 1/2 inch to 3 inch
• D. 3/4 inch to 1 inch

Answer: (A)

Inside the steam and mud drum, generating tubes must be a size that provides enough mechanical strength, clearance for proper steam–water separation, and room for cleaning and inspection. The permitted range of 1 1/2 inch to 2 inches strikes that balance: it yields tubes sturdy enough to withstand boiler pressures, while leaving adequate space in the drum for sludge removal and for the flow paths that separate steam from water. Smaller tubes would be harder to inspect, prone to clogging, and more difficult to clean, increasing maintenance issues and flow resistance. Larger tubes would crowd the interior and reduce the drum’s ability to separate steam effectively and would complicate fabrication and support. So, 1 1/2 to 2 inches is the standard size range that fits practical maintenance, safe operation, and efficient steam generation.