What is a function of the valves found forward of the deck seal?

The function of the valves located forward of the deck seal is to prevent backflow. These valves are essential in maintaining the integrity of the cargo system by ensuring that liquid or vapor does not flow back into the tank from the deck seal area. This is crucial for safety, as it helps to avoid contamination of the cargo and prevents the release of potentially hazardous substances into the engine room or environment.

In liquid cargo operations, maintaining proper flow direction is paramount to preventing spills and ensuring the efficient transfer of materials. These valves create a barrier that effectively stops backflow, which can occur due to gravitational forces, pressure changes, or other operational factors.

The other options represent functions that, while important in various aspects of fluid handling or tank operations, are not the primary focus of the valves located forward of the deck seal. For instance, pressure control may be managed by different pressure relief or regulating valves, and returning vapor pertains to vapor recovery systems, which have separate components designed for that purpose. Similarly, regulating temperature generally involves equipment such as heat exchangers or heaters, rather than the basic function of the deck seal valves.