(53ae) Hexsol Innovative 'extra Extra Strong' TLE

The traditional solutions for the mechanical configuration of S&T type TLEs make use of either membrane (thin, flexible) or stiffened tubesheets.

Each of the noted solutions has pros and cons: so either mitigation of secondary stresses at the expense of increased primary stresses are favoured or viceversa.

The traditional solutions for the water inlet in upflow S&T TLEs make use of either special arrangements to enhance the velocity on the bottom (hot) tubesheet (‘channeled’ design or special inlet baffle at calibrated distance from the tubesheet) or adopt a pure axial up-flow mode in pipe-in-pipe configurations.

Still, all solutions are susceptible of localized corrosion.

The traditional solutions for the water+steam outlets in upflow S&T TLEs make always use of one or two risers located at lower elevation with respect to the top (cold) tubesheet; so that downflow of the two-phase mixture is physiological and may originate flow instability/ blanketing in some of the transient conditions.

The classical issues experienced by End Users during operation can be finally summarized as follows: erosion on the gas-side, corrosion on the water-side, overheating of the inlet tubesheet, maldistribution in the tubes with consequent reduced running length between operational cycles.

Shortly, reduced reliability/ life-time.

The innovative XXS (extra-extra strong) TLE, designed and patented by HExSol and fabricated by Ofmeco, is aimed at presenting a unique compromise between the pros of the membrane and of the stiffened concept, dropping all cons; and at identifying an ideal water and water+steam flow with the elimination of any downflow section; and finally permits an optimal/ balanced redistribution of the cracked gas between all the tubes minimizing coke formation at bundle periphery.