How Guichon performs on steam crackers


Steam cracking is the first step to produce the simplest olefin: ethylene. It is one of the simplest of all the olefins and present everywhere around us. It is used as base product for several applications: Plastics, paints, solvents, packaging, cosmetics… The worldwide ethylene demand is now over 140 million tons per year and is still growing by 4-5% every year!


The good realization of this first transformation is played out in the performance of installed valves and in particular valves called “critical”.

ethylene process scheme

The most critical valves on a steam cracker are:

  1. The Transfer Line Valves (TLV) – Installed between the furnace header and the main column.
  2. The Decoke Valves (DV) – Installed on the specific decoke line. A security small decoke valve (SDV) is sometimes installed to prevent any overpressure.

These valves should meet the following requirements from the process side:

  • Operable under High Temperature (400°C or even more, depending on cracker feeds).
  • Zero leakage requirement (even after 6 years of operation)
  • Double-Block and Bleed feature on the main transfer line (TLV).
  • Material have to be resistant to corrosion and pitting caused by low pH condensate.
  • Valve body shall be resistant to thermal cycling.
  • Transfer Line and decoke valves shall be linked together and synchronized.

In both cases, the technical challenge on the process is mainly oriented on coke particles. Effluent is a three-phases flow: gas, quench oil and coke particles.

Regarding operation, the main challenge is to design and build a valve suitable for 6 years of operation in these process conditions. There is no time for any maintenance during plant operation and the downtime should be reduced as best as possible.


To design reliable transfer line and decoke valves with minimum maintenance operations and downtime.

With more than 90 years of industrial know-how, Guichon Valves designs and manufactures tailor-made valve solutions installed on steam cracking units for more than 40 years. All of them still operate at a good level of performance and reasonable maintenance and operating costs.

Added to this is a team of experienced technicians working around the world to help customers maintain their cracked gas isolation valves.

tlv guichon valves after maintenance

Recent intervention on a  36” TLV and a 10 ” DV installed in 1990

  • Through conduit slide valve (with substitution ring allowing full bore at fully open position)
  • EURAL II sealing rings
  • Internal tightness to avoid coke accumulation into the valve body.
  • Back seat system to protect the packing gland at full opening.
  • Thermal dissipation system upstream from the packing gland.
  • Purge system allowing the valve’s cleaning as well as a positive insulation performance protecting sealing surfaces.
  • Special body, designed and calculated to avoid any risk of thermal distortion.
  • Simple and reliable design with low cost, easy to carry out on site maintenance.
  • Electric type actuator designed and manufactured by ROTORK, and spring box for the decoke valve designed and manufactured by GUICHON VALVES.
  • Mechanical linkage and synchronized valve strokes. (Between Transfer Line & Small Decoke Valve)
  • 100% custom design, simulated by our engineering office and manufacturing in our workshop in Chambéry, France.

During the last plant turnaround, Guichon Valves is proud to see again zero leakage (testing pressure 4 bar – fluid: water) even after 30years of operation!

Recent intervention on a  36” TLV and a 10 ” DV installed in 1990