The dial of the pressure gauge on a high-pressure boiler should be graduated to no less than how many times the pressure at which the safety valve is set?

The pressure gauge on a high-pressure boiler should be graduated to at least 1.5 times the pressure at which the safety valve is set in order to ensure accurate monitoring and safe operation of the boiler system. This graduation allows for a safety margin that accounts for unexpected pressure fluctuations and provides confirmation that the pressure does not exceed the safety valve setting.

By graduating the gauge to this level, operators can quickly assess the operating pressure and be alerted to rising pressures that could indicate a potential issue, while still ensuring that the reading is within a safe range. This practice helps to prevent failures or malfunctions that could arise if the pressure approaches or exceeds the safety valve setting without proper monitoring.

Graduating the dial to lower multiples, such as 1.2 times or 2 times, would not provide adequate safety margins, while higher multiples, like 2.5 times, would be excessively cautious without significant benefit in most operational scenarios. Thus, the 1.5 times graduated reading strikes a balance between safety and practicality in monitoring boiler pressure.