Suggested Response - Q5

**How would you go about selecting the right materials for an application? For this exercise, use a mash conversion vessel (MCV) as your example. Be sure to show the reasoning behind your process.

Response:
Before selecting a material, it is important to define the properties required. For a mash conversion vessel there could be a number of components so let us break these down first:

  • The vessel

  • Heating surfaces

  • Support structures

  • Insulation

For each of these components the following material properties are important:

  • The vessel

    • Hygienic surface, smooth and easy to clean.

    • Resistance to heat and cleaning chemicals such as caustic and acid.

    • Material must possess good strength and reasonable ductility.

    • Material must be easy to form as sheets will have to be bent.

    • Material must be able to be welded.

  • Heating surfaces

    • Heating surfaces require good thermal conductivity to aid heat transfer.

  • Support structures

    • Support structures have to be strong to carry the heavy load of a full MCV.

    • Support structures need to potentially withstand a hot and humid environment with frequent external cleaning.

  • Insulation

    • Insulation must be suitable for use in a hot environment as it will be in contact with steam or other heating utilities.

Thus, the options for materials that meet these criteria are:

  • The vessel

    • Stainless steel SS316L is the best choice as it meets all the criteria.

  • Heating surfaces

    • Although the thermal conductivity for stainless steel is not as good as other metals such as copper, it is adequate. Heating surfaces are subject to fouling and may require more regular cleaning. This makes SS316L the obvious choice for this application.

  • Support structures

    • Mild steel, galvanised steel or stainless steel could be considered from a strength perspective. Given that it is a wet environment, galvanised steel would be more resistant to corrosion. Stainless steel could also be considered but as this is not a product contact surface, the extra cost may not be justified.

  • Insulation

    • This is a hot application so rock wool would be the obvious choice.

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