LLH odd question....

There is no such thing as a dumb question.

But someone else is going to have to answer this one....................

Sure you could. Typically you want to use the LLH as a multifunction device, more bang for your bucks.

\The air removal vent is at top, so you want the warmest water at the air removal portion. Dirt removal at the bottom where the drain cock is. Catching dirt and debris as it returns from the system before it can get into the boiler, pumps, etc.

Assuming that you are using a LLH that has the media inside to increase the function and performance?

Better yet get a 4 in 1 device Air, dirt, hydraulic separation, and magnetic separation.

yes they could be staggered. In the case where both input and output are exactly the same gpm (rarely) the flow is straight across, no mixing or separation is taking place.

Staggering them would possibly allow more buffering, but very little in a sep that holds 3 gallons.

True buffer tanks, like the ones built for chillers, have baffle plates built in to force the flow through the entire tank.

It's a bit tricky building a tank to serve as both a separator and buffer, especially with varying flows. Separation is easy, but getting the whole capacity involved as a buffer, not as easy. If both in and out flows are identical not much mixing in the tank, same as a separator. In the off load cycle you would start buffering some.

I like the two pipe buffer tank concept better IF you plan on a lot of different flow rates. The separation function actually takes place outside the tank in a big wide spot in the interconnection piping. The tank has a better "at bat" for buffering.

Once you build a buffer tank to also act as a separator however, you would not want a baffle inside. So it really comes down to what you are trying to accomplish. The separator was intended to be a step or two above closely spaced tees, offering that separation but adding more features and benefits.

Is it all welded up with removable top or bottom? if so a composite media could be installed.

If you need to weld on the piece with media inside you want stainless. Stainless seems to be the best choice, it holds up well to all types of fluid conditions.

How much do you need, I might has some misc pieces.

McNichols is where you can source all sorts of speciality mesh and expanded metals, they have locations across the US.
I've been to the one in Chicago area, they allow walk-ins, they cut and fab there also, great selection of unusual metals.

www.mcnichols.com