In what conditions can nonmetallic piping NOT be used in NH3?

Nonmetallic piping can indeed be used under various conditions; however, the key aspect to consider with ammonia (NH3) is its reactive nature and the limitations posed by the material properties of nonmetallic pipes.

Nonmetallic piping, such as certain plastics or composites, is limited in its application due to several important factors when it comes to ammonia transmission. One of the primary concerns is the chemical compatibility of the material with ammonia. Many nonmetallic materials can degrade or become brittle when exposed to ammonia, particularly in high-pressure situations or at elevated temperatures.

For this reason, there are specific scenarios—such as high pressure or high ambient temperatures—where nonmetallic piping would not be suitable for use with ammonia. Furthermore, while some low ambient temperatures may be permissible, they can also pose challenges, such as material brittleness under very cold conditions. Thus, the broad declaration that nonmetallic piping can't be used "at any time" rings true, given the inherent limitations that nonmetallic materials face when dealing with ammonia under variable conditions.

This understanding is critical for safe and effective piping system designs that meet regulatory standards and ensure operational safety in systems handling ammonia.