Steam Boiler Steam Line Velocity

[BronYrAur]

I have a 15 psig steam boiler that is approx 550 #/hr. It has a 4" flanged steam connection. I will have 2 of these boilers manifolding together, and my manifold header is only 3" (based on sizing 1,100 #/hr at a velocity in the 4000-6000 fpm range). I'm guessing the actual steam riser off the boiler is larger to help reduce water carryover. Is that correct? Is there a target velocity for the steam riser, or are you just supposed to match the connection on the boiler?

I assume it would be a bad idea to reduce the size of the steam riser off the boiler, correct? It just looks odd that I have have two boilers, each with a 4" steam line connecting to a 3" header.

Am I missing something here?

 

[ione]

A so called dry pipe (a pipe with holes or slots placed in the upper part of the steam place) is used in steam boilers to promote steam/water separation. A 4” outlet for a boiler with an output of 550 #/h at 15 psig seems definitely oversized to me (you should be comfortable with 2”). As far as the connection header, I usually size them for lower velocity than those you’ve quoted in you OP, that is approx 3000 ft/min. In you case the connection header should be 4”.

 

[steamdog]

The outlet header on the boiler may have been sized so that the same boiler can be used on lower pressure steam, this way they can have one standard for all rated operating pressures. Other than cost, there is no real problem with an oversized flange on the boiler outlet.

 

[BronYrAur]

I'm not concerned that the opening is "too big". I would like to run smaller pipe and am wondering if reducing would be a problem. I was thinking of sticking with 4" pipe down to the water inlet (which is 2-1/2") to create my Hartford Loop. I was going to tap off the top of that Hartford Loop with a 3" and run it up to my 3" header for both boilers. See attached. Thoughts?

 

[ione]

Can't see anything wrong in your arrangement. You can for sure live with your 3" reductions, working with that load at that pressure. As I've told before, I'd only go for a bigger diameter of the common header. Lower velocities (3000 ft/min at full load) in the header facilitate entrained moisture to fall out.

 

[BronYrAur]

Thanks for your help!