As you may know we are facing some

As you may know we are facing some problems on Tx and Sz with refractory. We are still investigating the root cause of the various problems but the potential causes are listed below :RK : Instability of the bricks – wrong design of the expansion jointsAs you can see on the attached calculation depending on operating condition the expansion joint is proven to be too large which facilitate the brick instability.The lower is the RK internal temperature the bigger is the clearance -> the more unstable are be the bricksRK shell temperature : the interesting point of this calculation is the calculation of the metal shell temperature. As you will see the external temperature is quite high (only one layer of brick on Tx &Sz) which raise the question on the design temperature of the RK shell. Basically if we refer to the attached calculation the external temperature is between whereas most of the time 250 deg. C is the temperature considered for the design. The above 2 items MUST BE checked and confirmed during the design -> Contractor shall demonstrate the calculation of the expansion joint + justify the design temperature of the RK Shell SCC : It appears that the design temperature for the metal shell considered by contractors is generally 150 deg. C which might be too low and generate corrosion.Again the design temperature of the SCC metal shell MUST be calculated and demonstrated by the contractor.