Erosion and Corrosion

Ceramic

Another possibly might be rubber-lined or -coated components. You could ask a rotary valve mfr (e.g., Semco) for recommendations.

...plus this isn’t leading edge technology. There must be other installations at the facility and at other similar ones where a wealth of experience and even local standards become apparent.

The telephone is the ideal research tool to discover them.

Unobtanium!

Well, I'd probably be more inclined to go with Cargonite 312™.

There is a critical shortage of Unobtanium, now that the fearless leader wants to build spaceships out of it.

For rotary air locks go with the suppliers recommendations but make sure that the seals are fitted with a reliable air supply to create a positive bleed into the valves through the seal which stops product from entering the seals. Also belt and braces with a spare set of seals on hand at all times. This is the part that fails most frequently and no matter how methodical you are about keeping the seals clean they will fail regularly.

Steel is the cheapest way to go for straight sections of pipe work. I have never used the special abrasion resistant grades and there are installations I designed 35 years ago still running without problems. The bends only wear on the outside curve but long radius bends wear less. There are lots of bends on the market with modified outer curve internal faces but they are expensive and wear out eventually requiring an expensive replacement which needs to be factored into the operational costings. A cheaper alternative is to use a short section of rubber hose connected by flanges to the steel pipe at each bend. These need to be rotated by 90^o every few months so you even out the abrasion and get 4x the life that you would normally expect. This is not as arduous a duty as it seems because with all the other types of bends you have to break down the bend to inspect for wear at regular intervals. I had one client who failed to do this and the fines for polluting the district with tonnes of cement pouring out of a failed "hardened" bend were over five times the combined lost product cost, replacement costs and down time losses. The other advantages are: when the do eventually need replacement (before they fail and you can monitor the degree of wear each time you rotate the hose) the replacement part is very low cost as you reuse the flanges, bends can be longer radius than what is available off the shelf, the tolerances when installing can be looser as the rubber takes up the slack, non-standard bends (e.g a 57^o bend) make routing the pipe much easier and possible shorter thus making further savings.

Is there a prize for getting the right answer?

Take your pick :

A wooden spoon. A red lantern. A pickle boat. A dusty bin. A zonk. A clunk. A blankety blank cheque book and pen. A rubber duck. A box of washing powder.

Hmmmm. It’s so difficult to choose...