What keeps the manway doors of the boiler drums in place during operation?

The correct answer highlights that boiler pressure plays a crucial role in keeping the manway doors of the boiler drums securely in place during operation. When the boiler is in operation and pressurized, the internal steam pressure exerts a force against the manway door. This pressure creates a sealing effect, ensuring that the door remains tightly closed and preventing any leakage of steam or water from the boiler system.

As the pressure increases, it effectively pushes the door tighter against its sealing surfaces, enhancing the integrity of the seal and contributing to the overall safety and functionality of the boiler. This reliance on pressure is fundamental in boiler design, as it ensures that manway access points remain sealed under the operating conditions typically encountered during use.

In contrast, while bolting force, force on the yoke, and strength of welds are all important factors in the construction and assembly of a boiler, they do not actively maintain the door's position during the high-pressure operation. Instead, they serve to hold the structure together and support the components in non-operational scenarios.