(97c) Cracking Furnace Gasket Selection – A Key Factor in Furnace Life Extension

          Flanges on ethylene cracking furnaces are necessary for proper maintenance, and offer specific challenges in terms of leakage avoidance and safety assurance. On cracking furnaces, any gasket failure will require a shutdown for repair.  As both radiant coil and refractory service life are strongly impacted by thermal cycling, avoidance of gasket failure events can be a key to maintenance minimization and furnace life extension.

          The steam cracking process normally takes hydrocarbon feed from roughly 120 deg F to above 1600 deg F.  The thermal expansion of the heating surface requires provisions to absorb the resulting movement, which may result in significant stress on joints.  In addition, the furnace operation is cyclic in terms of thermal cycling as well as oxidation/reduction cycling, due to the intermittent decoking operation.

          The subject paper reviews the common flange types and locations on a cracking furnace, and front end piping, and outlines important considerations for gasket selection.  Gasket solutions for each location are presented, which consider the fluid, the operating conditions, code requirements and safety related issues.