What characteristics should a positive cutoff valve have to operate correctly?

A positive cutoff valve is designed to prevent the flow of liquids or gases when not in operation, ensuring safety and efficiency in aerosol applications. For such a valve to operate correctly, it should have low negative pressure characteristics.

Low negative pressure allows the valve to maintain a controlled environment, helping to ensure that the system does not draw in unwanted substances or cause leaks. In practical terms, a valve operating under low negative pressure can effectively seal off the flow, enabling a reliable stop when needed. This also helps in maintaining the integrity of the pressure system within the equipment, ultimately contributing to better performance and safety during aerial application activities.

In contrast, characteristics like high positive pressure or high negative pressure could lead to malfunctioning of the valve. High positive pressure might overwhelm the valve and cause it to fail or leak, while high negative pressure could create a vacuum effect that may not reliably isolate the flow, leading to potential hazards. Thus, low negative pressure is the ideal characteristic for the proper functioning of a positive cutoff valve.