What protects the valves of compressed gas cylinders from the weight of upper pallets?

The correct answer is collars. Collars are fitted around the valve area of compressed gas cylinders to provide vital protection against impacts and weight from items placed above them, such as pallets. They are designed to absorb shock and prevent damage to the valves, which are critical for the safe dispensing of gas from the cylinder. Without the protection offered by collars, the valves could be accidentally damaged during handling or storage, leading to potential safety hazards or leaks.

While bumpers, caps, and guards may offer some form of protection, they do not specifically address the issue of protecting the valve from weight or impact in the same manner as collars do. Caps are primarily designed to cover the valve during transport and storage to keep contaminants out, while guards are generally used to shield the cylinder itself. Bumpers may help cushion impacts but do not provide the structural reinforcement that collars do around the valve area.