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As the CDC design evolves and final decisions are made, it is important that appropriate materials are selected along the way. The CDC administers chlorine, alum and in the future saturated lime, making material selection a critical part of this design. Additionally, there are a plethora of fitting styles available on the market. Cost, longevity, ease of use and availability are all important considerations. It is important to have a working knowledge about materials, pipes, tubing and fittings before any decisions can be made. This information should be posted on the wiki as a reference for future teams.
A suggested list of materials for inclusion in the database is::
*PVC
*Polyethylene
*Kynar
*Polyamide
*Acetal
*Brass - Include various types
*Stainless Steel - Include various types
At a minimum, chemical compatibility between these materials and chlorine, alum and lime needs to be established and documented. Material cost should also be discussed. Availability is more difficult to quantify but it is important to avoid specialty fittings or materials. This list should not be considered comprehensive; it should be updated as the project evolves.
In regards to fitting styles, some key Key points to consider:
*Compression fitting are for use on rigid tube. They are currently in use to connect the float valve in the CH Tank. Elimination of compression fittings is ideal as they are made up of a nut and two small ferrules which must be installed the correct way in order to obtain the seal. It is too easy for one of these components to get lost, dropped etc, rendering the fitting useless.
*Quick-connect fittings are also used on rigid tube. Their longevity is in question as is their availability outside of the US. Use of PEX rigid tubing is becoming increasingly more popular in water distribution systems and improvements on fitting styles and availability is likely to follow.
*Barb fittings are quite stout, easily available and are fabricated from many different materials. They are used on flexible tubing (based on the ID of the tubing, not the OD.) The biggest drawback to a barbed fitting is that they can be difficult to remove from the tubing once assembled, especially after a long period of time. It is not uncommon to have to slice the tubing off from around the barbed fitting. This is not necessarily a show stopper, especially if a connection doesn't need to be undone very often.
*PVC pipe is ubiquitous; it is currently used throughout the existing AguaClara design, is available world-wide and is suitable for use with all process chemicals involved. The current line-of-thought is to use 1/2" PVC rigid pipe and socket solvent-weld fittings for all delivery pipes (i.e. from chemical stock tanks to the CDC) and flexible tubing within the CDC instrument.. When needed, PVC threaded to barb adapters will be used to convert to flexible PVC tubing.
Once the materials and fittings are decided upon, this information needs to be incorporated into the Automated Design Tool. The goal is for the design tool to eventually include the CDC and to have a material list and AutoCAD drawing of the installation included as part of a standard design package.