Where must the relief valve of stored cylinders be positioned?

The relief valve of stored cylinders is designed to handle excess pressure caused by temperature increases within the cylinder. When the pressure inside the cylinder rises, the relief valve must be positioned to allow gas to escape safely to prevent a potentially dangerous buildup of pressure.

Positioning the relief valve in the vapor space of the container is particularly effective because, as liquid LP-Gas is heated, it generates vapor that increases pressure. The vapor space is where this generated pressure first becomes significant, and if the pressure exceeds safe levels, the relief valve can open to release that vapor, thus protecting the integrity of the cylinder and preventing a catastrophic failure.

In contrast, having the relief valve in the liquid space would not effectively relieve pressure, as gas buildup would not directly interact with the liquid phase. Similarly, placing the valve in the bottom or the side of the container does not facilitate proper pressure management as effectively as positioning it in the vapor space. Therefore, the correct choice emphasizes safety and functional efficacy in pressure regulation of LP-Gas cylinders.