A liquid transfer hose equipped with a shutoff valve at the discharged end must have what installed in the line?

In a liquid transfer hose equipped with a shutoff valve at the discharge end, a hydrostatic relief valve must be installed in the line to ensure safety and prevent excessive pressure build-up.

When liquid propane is transferred, the flow can create pressure in the system. If the shutoff valve is accidentally closed while the pumping is still in progress, it prevents the liquid from flowing out, which could lead to pressure accumulation in the hose and system. In such situations, the hydrostatic relief valve acts as a safety mechanism by automatically relieving pressure when it reaches a certain threshold, allowing the excess liquid to return to the storage tank or an approved location. This helps to mitigate risks of ruptures or leaks due to high pressure, thereby enhancing safety during propane transfer activities.

The other options, while possibly relevant in different contexts, do not specifically address the need to handle pressure build-up during liquid transfer with a shutoff valve. A pressure gauge indicates the pressure but does not relieve pressure. A flow restrictor is used for managing flow rates, and a filter screen is generally utilized to prevent contaminants from entering the system. However, neither of these components addresses the safety concern inherent in high-pressure situations caused by the presence of a shutoff valve.