(43d) Radiant Cracking Tubes – Quality from the Foundry

Nickel chromium alloy tubes have refractory properties which make them an ideal material for ethylene pyrolysis coils. These alloys are typically cast. And, with no universally accepted standard to cover the manufacturing and testing of cast cracking tubes, individual users have developed their own specifications for inspection and testing. The applied testing has varying degrees of relevance and effectiveness.

Individual cast tubes are custom made so it is important that the manufacturing methods are fully understood by the customer to evaluate tube quality, without adding unnecessary costs to the product. The tube chemistry is a strong factor on tube quality, and since each cast tube is poured individually, control of variation in chemistry is vital. Subsequently, physical inspection methods in the as-cast, machined and welded states are important to ensure the quality of the castings and the final assembly.

This paper addresses the tube manufacturing process including casting, machining and fabrication. The typical inspection operations are also covered.