According to ASME code, a high-pressure boiler with more than 500 square feet of heating surface shall have what safety feature?

High-pressure boilers with a heating surface exceeding 500 square feet are required by the ASME code to be equipped with two or more safety valves. This safety requirement is designed to ensure that in the event of excessive pressure buildup within the boiler, there are sufficient safety mechanisms in place to relieve that pressure effectively and safely.

Having multiple safety valves provides redundancy, minimizing the risk of failure. If one safety valve were to malfunction, the presence of additional valves ensures that the boiler can still be vented, thereby preventing potentially catastrophic failures such as explosions. This design consideration is critical to maintaining safe operation and protecting both the equipment and personnel working around high-pressure steam systems.

The other options do not meet the safety standards as outlined by ASME. One safety valve could be inadequate to handle the potential pressure release needed for large boilers. A pressure relief valve, while important, does not serve the same function as safety valves for high-pressure applications, which specifically mitigate excessive pressure in the boiler.