(a) Maximum allowable number of broken staybolts. No boiler shall be allowed to remain in service with two broken staybolts located within 24 inches of each other, as measured inside the firebox or combustion chamber on a straight line. No boiler shall be allowed to remain in service with more than 4 broken staybolts inside the entire firebox and combustion chamber, combined.

(b) Staybolt replacement. Broken staybolts must be replaced during the 31 service day inspection, if detected at that time. Broken staybolts detected in between 31 service day inspections must be replaced no later than 30 calendar days from the time of detection. When staybolts 8 inches or less in length are replaced, they shall be replaced with bolts that have telltale holes 3/16 inch to 7/32 inch in diameter and at least 1 1/4 inches deep at each end, or that have telltale holes 3/16 inch to 7/32 inch in diameter their entire length. At the time of replacement of broken staybolts, adjacent staybolts shall be inspected.

(c) Assessment of broken staybolts. Telltale holes leaking, plugged, or missing shall be counted as broken staybolts.

(d) Prohibited methods of closing telltale holes. Welding, forging, or riveting broken staybolt ends is prohibited as a method of closing telltale holes.