Yeah, I've burnt up several of those cheap 24v pumps. They work well for a few months, but that's about it. I'm not using the pump right.... No, I'm not a pro brewer, however i'd note that you never see any pro breweries using Igloo cooler mash tuns either, LOL. The sight glass makes a great vaccum gauge. I never have any efficiency problems or channeling issues, never use rice hulls. Maybe you just had a better cooler false bottom than I did.....
Ive been using these 24v pumps for over 4 years without issues, Ive burned one up out of stupidity but Yes you have to be doing something wrong to keep burning them up, They are rated for like 40,000hrs of run life..
Obviously there arent large cooler based pro brewing equipment but there are many 3 and 5 bbl and larger brewery setups with insulated mash tuns.. From and engineering standpoint stainless has to be used on that level for a number of reasons its not a design difference so much as putting a non functional sight glass (as far being a sight glass anyway) in to act as a vacuum buffer because your pulling liquid too fast..
Im not sure if your kidding or you dont understand the point of what I was saying but there is a much bigger operational difference between having the sight glass or not and what you mash tun is made out of. You simply shouldnt need the "vacuum indicator" at all as pulling that hard only promotes channeling and hurts performance as well as causes stuck mash tun flow and (as you already seem to know) can burn up pumps.
I used a simple bazooka tube in my mash tun for a while and then went to the $30 standard 12" domed FB from my local HBS store... maybe the second piece of finer stainless braid helped keep the grain out of my pumps but thats about it.
I have since replaced my cooler with a 16 gallon stainless mash tun for two reasons, larger diameter FB and BLING factor... Seriously I had upgraded my other kettles and equipment to the point where the cooler just didnt make sense, plus I can brew bigger beers now. with a WORKING rims the whole point of an insulated mash tun is no longer justified.
Some folks use both, they spend hundreds on the insulated stainless mash tuns and use them with herms or rims too, but then again some folks apparently like spending time scooping all the grain out of large insulated stainless mash tuns instead of just carrying the thing outside and dumping it.. For me only one form of percise temperature control is enough. especially if it streamlines my brewday instead of needlessly complicating it. I alsways had plans to open a nano and experimenting with herms and rims setups at the homebrew level made more sense due to that but yeah you dont need either with a cooler..