Risers & manifold

Snowmelt

I just watched the Weil McLain with the clear class demo. Also watched one of dans 25 minute Steam video, let me ask 3 questions.
1. Dan said he likes to see a 24 inch minimum riser out of the boiler instead of 24 inch from water line. At the same time I like to put a Union on both my risers and add a nipple (4 inch) any harm on going higher then 24 inch.
2. the Weil McLain I think they’re all 3 inch tappings. Any reason why I shouldn’t go 3 inch instead of bushing down or reducing to 2 or 2-1/2 on smaller boilers.
3. On the manifold any harm on going 1 size larger 3 to 4 inch with a few nipple to piece everything together, give the steam some room in pipe to separate from water?

Jamie Hall

On one, 24 inches is sort of a rule of thumb kind of thing. One wants enough riser to let the really big bloops a chance to get their act together and drop, but how much that is really doesn't have much real engineering background. On the other hand, there isn't much point in going too tall, as any water drops (or bloops!) should be taken care of in the manifold (or header, as usually called, or steam drum in some applications).

On two, within reason the bigger the better -- and if the boiler is three inch tappings, go for it.

On three. Ah. The manifold, as you call it, or the header as it is usually called, or the steam drum. I believe the overall consensus is to go at least one size bigger for a single riser -- and two sizes might be even better, particularly for two risers. The objective here is to really put the brakes on the velocity, so that any water droplets, even small ones, have a chance to settle out and return to the boiler. Some settling is helped, of course, by the right angle takeoffs for the steam mains -- but even that is somewhat defeated if the velocities are high, as the turbulence keeps the water entrained. In power boilers, and in some heating boilers, there will be a true steam drum (my Cedric has one) which is MUCH larger than the risers but these aren't usually needed for most heating boilers, and are very difficult to actually create (Cedric's is a leftover from the original huge HB Smith boiler which was installed in 1930 -- long gone now, of course(., Whatever, there must also be some pitch to one end (parallel to the steam flow), and a free drain at that end back to the boiler. And it all should be well insulated.