This selection can be the influenced by discussions with the mills and/or experts and are often based on results of laboratory tests and experience.

Vessel parts (e.g. vesselheads) are produced by cold forming or hot forming with a possible subsequent heat treatment. These production steps can change the material properties.

The engineers and designers must be aware of the influences on their vessel!

1.2.1 Interpretation of Design Codes

The formulas mentioned in the design-codes to calculate the deformation grades for vesselheads are different from the practical experiences.

The design codes are not clear if the weld seam is to be considered as a part of the plate-material

1.2.2 Mechanical and corrosion requirements

Mechanical properties and corrosion resistance values will change after cold forming.

Are the designers aware of the consequences of cold forming especially a decrease of the elongation-properties.

What kind of corrosion tests are required by the designer and will these tests fulfill the requirements after cold deformation?

Question :

Is heat treatment after cold forming necessary, contrary to the requirements of the design codes?

According the European design codes vesselheads must be heat treated after cold forming due to the properties of the carbon steel. The ASME design code does not have this requirement (in most cases).

Heat treatment parameters (e.g. temperature, soaking time) must be suitable for the carbon steel as well for the stainless steel clad layer and weld seam (if applicable).

However in practice this will not always be considered or recognized as a problem.

Mechanical and corrosion properties will change due to heat treatment.

Question :

Are the corrosion properties of the explosion bounded plates taken into account after heat treatment by the pressure vessel part producer?