What device safeguards the seal from failures caused by a plugged nozzle?

The internal bypass is the correct choice because it is specifically designed to protect the seal in a system from failures that might occur due to a plugged nozzle. When a nozzle becomes obstructed, it can create excessive pressure within the system, potentially leading to leaks or seal failures. The internal bypass allows the fluid to reroute back into the system, relieving pressure and preventing damage to the seals and other components.

This mechanism is essential because it helps maintain the integrity and functionality of the system even when part of it is compromised. In contrast, the other options do not serve this exact protective function. An overflow valve primarily deals with excess fluid to prevent overfilling, while a drain valve is used for removing fluid from a system. Meanwhile, a pressure relief valve is concerned with excess pressure but generally does not reroute flow internally to protect seals from specific obstruction issues. Therefore, the internal bypass is the key element that helps safeguard against failures linked to blocked nozzles.