What innovation eliminated the need for staybolts in box headers?

The innovation that eliminated the need for staybolts in box headers is sinus headers. Sinus headers are designed with a distinct sinusoidal shape that allows for the distribution of thermal stresses more evenly across the header. This design significantly reduces the internal stresses that occur due to temperature variations and pressure, which would traditionally require additional structural support, such as staybolts, to maintain integrity and ensure safe operation.

Through the use of sinus headers, the requirement for staybolts is no longer necessary because the headers can handle the stresses without additional reinforcement. This leads to a more efficient and streamlined design process, simplifying maintenance and reducing the potential for points of failure in boiler systems. The ability of sinus headers to accommodate movement and expansion without compromising the structural integrity of the assembly is a key advancement in boiler technology.