What should be verified before installing a safety valve?

The correct choice focuses on verifying the relieving capacity of the safety valve before installation because this is crucial for ensuring that the valve can handle the maximum expected pressure that may occur in the system. The relieving capacity is defined by the manufacturer's specifications and must align with the safety requirements of the boiler or pressure vessel.

When a safety valve is installed, it serves the critical function of relieving excess pressure that could lead to dangerous situations, such as explosions or equipment failure. If the valve's relieving capacity is insufficient for the system's pressure conditions, it may fail to open when needed, rendering it ineffective. Therefore, confirming that the safety valve has an adequate relieving capacity specific to the application's requirements is essential for safe operation.

While the other factors, such as size and fit, model and brand, and manufacturing date, are important considerations, they do not directly address the operational safety and effectiveness of the safety valve in handling pressure scenarios. Thus, ensuring the relieving capacity is the most vital aspect prior to installation.