steam velocity

clammy

I was just wondering how many of you guys ever sit down before hand and fiqure out the steam velocity when piping the header on a steamer and if so what is the mimium fps that you have used with success .I know on one small steam i did recently i had it figured out with 2 2" riser and a 2 1/2 header and it came out mathmaticlly to about 11.52 fps that system is very quite and heats the house quite well and according to HO there hotter then they have ever been since living there .What is a safe mimium and what are the maximum velocity you guys use .I have always tried to stay below 15 fps thanks peace and good luck clammy

Al Letellier_16

figuring velocity

I figure that the manufacturer of the boiler knows best and I pipe it like they recommend. I don't usually get that technical when installing a new boiler...wish I had the time, but........

soot_seeker_2

Sometimes

...when I'm curious, have time on my hands or really get into a system, I'll calculate it.

Otherwise, if all is straight-forward, I'll follow the manufacturer's recomendation and upsize the header and often the risers.

Ed

T-O

I would agree with Al, manufacture's knows best.
Old pipe sizing handbooks featured charts showing the required pipe sizes based upon the connected load and the designed pressure drop, one ounce for 100 foot equivalent pipe length. In a low pressure steam system running at about 1-1/2 lbs PSI. the steam velocity is about 30 fps. If a system has 15 fps steam velocity the sizes of the pipes would be larger than the ones recommended on the chart and also there would be no pressure drop. On the negative size, I would think with the lower steam velocity, the system would have to run a little longer to fill, heat the pipes and reach all the radiators.
T-O
TO

Boilerpro_3

Look in the lost art

Dan has the charts in there, because the maximum recommended velocity varies with the pipe size. 12 fps was the old maximum, which generally is about 1/2 of the maximum at which water can fall back against steam.
Also, individual boilers vary greatly in water carry over. Noel's Slant fins run bone dry steam at 190,000 input with a single 2 1/2 inch riser, while the same size Durkirk will have heavy carry over into the header with that size piping.

Boilerpro

Patrick Linhardt, \"Linhardt's Field Guide to Ste

slow as she goes

Hi clammy,

Peace brother, you are a true purist. Keeping below 15 fps is surely old school.

In doing research for my field guide, I calculated the leaving velocity of many boilers per recommended specs. I found a lot of variance on the issue. In summary, the older the boiler, the more concerned they were with dry steam, and therefore designed for slow velocities. That's why the old steamers had large outlets, and plenty of them. Oh yea, and big chests.

The lowest I calculated was just around 10 fps. Most older boilers were around 25 or less. The modern jobs go up to 60 fps, but are generally around 50.

I recommend at or below 25 fps for dry steam, but allow up to fifty with care (close attention to near boiler details). Above that and you take your chances.

So rock on my friend. You are truely a hero in my book for keeping the speed down around the boiler, and going the extra step to calculate the results of your attention to detail.

Best regards, Pat