329 Pipe Hangers

Refineries heat crude oil by pumping it through pipes suspended in a natural-gas-fired furnace. Stainless steel hangers have traditionally been used to support

FIGURE 3.13 Tube (or pipe) hangers support flammable-fluid-filled pipes in refinery furnaces. Operating at higher temperatures, CFCC hangers improve safety and reduce downtime. Hangers supporting twin tubes are 18 in. wide and i in. thick, resulting in less weight and lower stress on fasteners.

these long horizontal tubes (Fig. 3.13). The hangers are exposed to near 1100°C (2000°F) in order to heat the oil to 815°C (1500°F). These temperatures are too close to steels limit and the hangers sag, oxidize, and become brittle. Sometimes they fail before 3 years, the required service time. Hanger failure results in burst pipes, fire, and explosion. CFCC pipe hangers enable higher furnace temperatures, resulting in increased crude throughput and higher production rates for the refinery.

The crude furnace consists of a firebox, which is refractory lined, steel or alloy tubing through which the crude oil is transported and heated, and metal tube hangers that support the tubes. A typical firebox environment contains nitrogen, carbon dioxide, and carbon monoxide along with smaller amounts of oxygen, water vapor, and sulfur dioxide. The furnace temperature is limited by the susceptibility of the metal tubes to thermal degradation.

After 8500 h exposure in a major refinery, a silicon carbide/silicon carbide CFCC had a flexural strength of 20 ksi, well above the required 6 ksi. The data indicates that they will perform the required 3 years, the time of their next evaluation.

The use of CFCC pipe hangers gives a 150°C (300°F) safety margin and a hanger weight of 3 lb versus 30 lb for steel, enabling a safer, reduced stress application.

CFCC pipe hangers offer thermal stability, dimensional stability, corrosion resistance, fatigue resistance, and light weight compared to steel. The use of CFCC pipe hangers will result in longer life, improved efficiency, safety, and reduced downtime and maintenance. In this application, safety is an added benefit.

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