What is the maximum allowable resistance to ground for a vessel grounding system?

The correct maximum allowable resistance to ground for a vessel grounding system is 25 ohms. This standard is significant because maintaining an effective grounding system is crucial for the safety and protection of pressure vessels from lightning strikes and electrical faults.

A grounding resistance of 25 ohms is often accepted in industry practices as it balances the need for safety with the practicalities of achieving a reliable grounding system. A lower resistance value, while potentially providing better lightning protection, can be difficult to achieve and maintain due to soil conditions and other environmental factors. Hence, 25 ohms serves as a reasonable benchmark that supports both safety protocols and operational feasibility.

In summary, the specification of 25 ohms reflects established industry standards aimed at ensuring adequate grounding without imposing unrealistic requirements that could lead to increased costs or technical challenges in system installation and maintenance. Understanding this ensures that operators and inspectors can effectively assess the grounding systems employed in pressure vessels.