California ICC UST Service Technician Practice Exam

What is used when there is insufficient slope on vapor return lines from dispensers to tanks?

1. Liquid collection point

2. Pressure regulator

3. Expansion joint

4. Vapor separator

The correct answer is: Liquid collection point

In cases where there is insufficient slope on vapor return lines from dispensers to tanks, a liquid collection point is utilized. This component serves as a mechanism to prevent liquid from collecting in the vapor return line, which can occur due to inadequate drainage. By incorporating a liquid collection point, any liquid that does inadvertently accumulate can be collected and directed back to the tank, thus maintaining the system's efficiency and preventing potential overfilling, pressure imbalances, or vapor lock conditions. The design of vapor return lines relies on gravity to help facilitate the flow of vapor back to the storage tanks. When slope is insufficient, two-phase flow can occur, leading to the undesirable situation where liquid fuel mixes with vapor. The liquid collection point can effectively manage this issue, ensuring that only vapor is returned to the tank while any liquid is safely diverted away for proper handling. Other components like pressure regulators or expansion joints do serve important functions in a fuel dispensing system but do not specifically address issues related to the slope of vapor return lines. A vapor separator is also more related to ensuring effective separation of phases but does not handle the accumulation problem directly. Therefore, the use of a liquid collection point is the most effective solution for managing insufficient slope in vapor return lines.