Tube insert and ferrule are the same products, a metal, plastic or ceramic tube that is inserted into the end of a heat exchanger tube to provide a specific function. The purpose of a tube insert is to either be sacrificial to the effects of inlet-end erosion, corrosion, impingement to induce a fluid to fall on the ID of a tube in a falling film exchanger; or to transfer extremely high heat past the tube sheet to the exchanger tubes. Each of the above applications requires a specific style of design. At NSI, we manufacture metal tube inserts for all applications, providing the necessary drawings required.
Even though there are some applications where plastic will perform satisfactorily, we have concerns of the stability of the product, its tendency to transfer erosion problems down the tube, its durability in an abrasive environment, and its reaction to elevated temperatures. A metal tube insert is more durable in these environments. In addition, ceramics perform well when the temperatures are extremely high, however they can be subject to breaking.