New level in our technological ability and know how – Estanc’s first ESW WOL vessel.


In the end of this years summer, in August, Estanc finished another significant and technologically challenging project- a 100 % inner WOL (Weld Overlay) covered processtank for petrochemical industry.

this double-walled carbon steel vessel has thick 50mm inner shell that is covered with two layers of overlay welding. Named demanding process was done using electroslag technology. We used weldingtape with 60 mm width and additionally covered pipeconnections with wol. The purpose of WOL is to give Carbon steel anticorrosion and antioxydative qualities. That gives a chance to use more agressive processmatter in the vessel.

Vessels outershell was fabricated out of 35 mm material. It’s working temperature is 375°C and working pressure 50 bars. Vessel itself weighs in at 45 tons.

To dive in the rabbithole, the manufacturing of this vessel faced following significant challenges that our team had to be faced with.

  • Preheated welding of the pipes that pass through both layers and their NonDestructiveTests. The NDT process took 7 level testing which involved visual testing, penetration testing and ultra sonic testing. NDT testing was out of the normal standard range. the named stainless steel piping welding with Inconel substance had to be used with AR gas backing. The results in O2 concentration between the two shells was finally achieved at a outstanding level of ~25 ppm that means 0,0025%.
  • For the sake of the thick materials and WOL the whole vessel had to be post weld heat treated (PWHT). We used 12 termopair detector to observe how the temperature was divided among the vessel. Walking through that process with minimal temperatureswings between the shells was a unique challenge both for us and for our subcontractors.

What we hope to demonstrate with this newspiece and the photoslider visualizing some of beforementioned challenges is that Estanc is always interested to reach new heights and to meet our clients needs.