In what situation are shutoff valves not required in boiler systems?

Shutoff valves in boiler systems are primarily used to isolate the boiler from the rest of the system for maintenance or emergency situations. In the case of low-pressure steam boilers, the requirements for shutoff valves can be relaxed due to the nature of low-pressure systems, which generally have less risk associated with failures compared to high-pressure systems.

When only a low-pressure steam boiler is installed, the risks are significantly reduced, and the code may not require the installation of specific shutoff valves. This is largely because low-pressure boilers operate under less strain, resulting in a lower likelihood of hazardous scenarios that might necessitate quick isolation of the boiler for safety.

In contrast, high-pressure systems often require more stringent safety measures, hence the need for shutoff valves is emphasized. Additionally, requirements may differ for public buildings and residential heating applications based on factors like occupancy, type of use, and safety regulations. Thus, a low-pressure steam boiler represents a situation where shutoff valves are deemed unnecessary according to the mechanical code.