Which type of stays are used in the heads of water tube boilers?

In water tube boilers, the head or header sections often do not require stays because their design typically allows for sufficient structural integrity through the use of tubes and headers. The headers are usually supported by the boiler structure and the pressure maintained within the tubes creates a balanced system that resists deformation. Hence, the lack of stays in these areas is appropriate for the designed function and operational conditions of the boiler.

Other types of stays like vertical, diagonal, or spiral stays are often used in different boiler designs, particularly in fire tube boilers and other configurations where additional support is required to handle thermal expansion and internal pressures. However, in the specific case of water tube boilers, the structure is inherently stable without the need for additional stay supports at the heads. This design consideration is vital to prevent unnecessary complexity and potential stress points in the boiler.