chemical plant pipeline devices

Googling "piping pigs" gets lots of hits. There are various construction materials, including polyurethane. That or another plastic might do well with residual amounts of nitric acid in a line. If metallic scrapers are involved, they might need to be replaced fairly often due to corrosion. If you approach a few pig suppliers, they can surely tell you more.

I am surprised that you have not gotten more contributions to your questions. With that said I will offer you my thoughts.

"Do chemical plants such as ones that are involved in the production of fertilizers utilize pigging devices (i.e to check for cracks in the pipes) because I haven't come across any."

A Chemical Plant that makes Fertilizer (or any other product) would be in the same physical "Process Plant" grouping as an Oil Refinery or a Petrochemical Plant. Process Plants by nature have very complex piping configurations in all sizes and ratings. These complex configurations also are littered with many, many branch connections and different types of valves and temperature probes that constitute an obstruction to the free passage of a "Pig". This is further complicated by the fact that there is no place to launch a pig or to retrieve a pig.

"I do know that the oil industry uses them a lot."

To clarify this point, The only part of the "Oil" industry that uses "Pigs" (to my knowledge) is the "Pipeline" industry. "Pigs" are used extensively in the cross country pipeline movement of all sorts of commodities. These include Crude Oil, finished petroleum products such as gasoline, Liquid Petroleum Gas (LPG), etc. Cross country pipelines are also used to transport chemicals such as Chlorine. The key point that makes the use of "Pigs" possible is that the pipeline is arraigned in a single line from point "A" to Point "B". This single line is not a straight line but it is normally the same size from Point "A" to Point "B". The same size allows for the different types of "Pigs" to travel through the without getting stuck. These pipelines are designed with "Pigging" in mind and have "Bends" instead of elbows to allow the free passage of the pig. The valves (when required in the pigging portion of the line) are the type that allows for the unrestricted passage of the pig. Far more important is the fact that any pipeline that is to be pigged, is designed with a pig launcher/receiver at each end. This launcher/receiver is a complex configuration that is placed at the interface between the Process Plant piping and the Pipeline piping and allows fir the inserting and removal of a pig.

"Also if they were to use them in the plants that produce fertilizers what type of material would be utilized in the making of the pigging device taking note that nitric acid may be present."

The best way to determine the best material for use in any given situation (or commodity) would be to contact a "Pig" vendor.