For a low pressure boiler, what does a data plate marked 6900 lb indicate for a safety valve?

When a data plate on a low pressure boiler indicates "6900 lb," it specifically refers to the capacity of the safety valve, expressed in pounds per hour (lb/hr). This measurement indicates the maximum amount of steam or water that the safety valve can safely discharge to prevent overpressure conditions within the boiler system.

Understanding the safety valve’s capacity is crucial for maintaining safe operating conditions. If the boiler generates more pressure than what the safety valve can relieve, it poses a risk of catastrophic failure. The lb/hr rating provides an essential guideline for ensuring that the safety valve is appropriately sized for the boiler’s operational parameters and can effectively mitigate pressure buildup.

The other options relate to different specifications that are typically associated with boiler operations but do not directly correlate with the 6900 lb designation on the data plate. For example, maximum pressure rating and design pressure of the boiler involve limits on pressure tolerance, while minimum safety valve setting refers to the lowest pressure at which the safety valve is allowed to open. These are separate concerns from the valve's capacity for discharging steam or water.