What must be provided to prevent boiler steam pressure from exceeding safe limits?

To ensure that boiler steam pressure remains within safe limits, automatic limiting devices are essential. These devices continuously monitor the pressure within the boiler system and can automatically adjust the operation of the boiler when pressure approaches unsafe levels. By intervening in real-time, they provide an efficient and reliable means of controlling the pressure without the need for manual intervention. This capability is crucial in preventing conditions that could lead to equipment damage or hazardous situations.

While other options, such as a manual control device, pressure relief valve, and safety pressure gauge, all play significant roles in a comprehensive safety system, they do not provide the same level of automated response to pressure fluctuations. A manual control device relies on human action to adjust pressure settings, which can lead to delayed responses. A pressure relief valve is designed to release excess pressure but only activates after pressure reaches a predetermined threshold, potentially allowing unsafe pressure levels to develop before it operates. A safety pressure gauge provides vital information about the pressure levels but does not have the capacity to take action on its own.

In summary, automatic limiting devices enhance safety by providing proactive, automatic control to ensure boiler steam pressure remains within safe operating limits, thereby reducing the risk of overpressure situations.