The Beauty of Orifices (with "undersized" steam boilers).......

The Steam Whisperer (Formerly Boilerpro)

Had the opportunity the last couple of days to make some additional upgrades to two 2-pipe steam systems in which we replaced grossly oversized and incorrectly piped atmospheric boilers with 2- Slantfin Intrepids with Heatwise Power burners.  Fuel usage already took a big drop from these improvements.  Now we had the chance to make the next step.....add orifices to all the radiator valves.  The system has about 800 EDR, long steam mains, and a fair amount of uninsulated steam main where radiation had been removed.  We were running about 175,000 output from the boiler (size based on Heat loss calcs) .  The home heated much better than with the previous oversized boilers (the basement no longer was roasting), but steam distribution was not very even.  After having calculated the EDR necessary for each space we sized the orifices to meter the steam appropriately to each radiator. 

After getting everything back together we fired up the boiler.  In about 15 to 20 minutes the radiator valves started getting hot....ALL OF THEM, ALL AT THE SAME TIME (except one that appeared to have a clogged trap).   The radiators appeared to continue to warm up evenly across the system (with the second floor a little light because we cut back the capacity of these radiators more).  After about an hour of continuous firing the system continued to heat evenly with the boiler at about 5 ounces. 

If we had used conventional boiler sizing methods we would of figured a boiler at about 360,000  input due to the radiation and extensive piping system, some without insulation.   Instead the boiler was sized to heat load and the orifices used to downsize the radiation, resulting in a boiler input of only 225,000, saving on the cost of the boiler and boosting efficiency by cutting off cycle losses. 

Its amazing what a handful of orifice plates and a partial day of work can do to permanently improve an 80 year old steam system.

Maybe next we till be able to upgrade to a modulating burner controlled by a modulating thermostat to completely eliminate off cycle losses and provide very stable heating to the space....just like outdoor reset on hot water systems.

Unknown

But Dave,

What about orifices with oversized banks of CIBB?

I look after a 3 unit Caravan system (super oversized), supplying CIBB banks that are up-to 26` long,, and to make matters worse, the supply to each bank is undersized.

The "anvil chorus" begins,,, so I run only 1 boiler(300K) input, on a system requiring 350K output@ design to keep all this(using Franks term), "knuckle-heading" quiet.

Even at this rate, obviously, I still had to use orifices. 

Steamhead

Orificing works

Frederic Tudor knew this in 1885. BP continues to develop this method. When we become Dead Men, we need to thank him, eh?



Dave, does your CIBB have the usual 3/4" connections? Are they feeding 26-foot lengths with one 3/4" connection?

Unknown

Frank

Yes.

The Steam Whisperer (Formerly Boilerpro)

They should work....

Just size the supply orifice to the required EDR to meet the calculated heat load of the space.  I would be concerned if your supplies are too small, but 26 feet of baseboard is probably about 90 EDR, which is only about a 5/16 orifice if using 2 inch Mercury pressure (1/2 psi I think).  5/16 is a whole lot smaller than a 3/4 inch supply. 



I would imagine just about any system would bang with that much extra boiler....things are just happening tooooo fast.   Cut boiler output and/or, if zoned, throttle the zones so they heat up slower.  I have found just cutting the operating pressure will allow the zone valves to throttle the steam enough to allow a system to quiet down.

tim smith

Re: orifices on steam system

Question for steam head & boiler pro. I have  a 30 unit bldg with vacuum pump and old firetube. Have hoffman 17c traps on all radiators and drips. Wondering what or if orifices are applicable or would be of benefit? We are getting ready to replace boiler and want to know if their are any other beneficial things we can do. Building load is appx 800,000 btu at od design. I don't have sq ft of radiation with me but i have at office. Any input appreciated. Tim

tim smith

Re: orifices on steam system

Question for steam head & boiler pro. I have  a 30 unit bldg with vacuum pump and old firetube. Have hoffman 17c traps on all radiators and drips. Wondering what or if orifices are applicable or would be of benefit? We are getting ready to replace boiler and want to know if their are any other beneficial things we can do. Building load is appx 800,000 btu at od design. I don't have sq ft of radiation with me but i have at office. Any input appreciated. Tim

tim smith

Re: orifices on steam system

Question for steam head & boiler pro. I have  a 30 unit bldg with vacuum pump and old firetube. Have hoffman 17c traps on all radiators and drips. Wondering what or if orifices are applicable or would be of benefit? We are getting ready to replace boiler and want to know if their are any other beneficial things we can do. Building load is appx 800,000 btu at od design. I don't have sq ft of radiation with me but i have at office. Any input appreciated. Tim

The Steam Whisperer (Formerly Boilerpro)

Tim.....

I'll e-mail you a couple of articles I wrote on the subject.  They are still in draft form, but get the ideas across, I hope.    I don't address vacumn specifically, but I believe the principles are the same.   I suspect you could vary the amount of vacumn to the system based on outdoor reset.  Also, you may want to look into a modcon steamer since you are running lower temps. I'd at least do Modulating input if its in the budget.      Rayes boiler is working on adding a condensing heat exchanger to thier, what appears to be, a very efficient design.  This, of course, assumes you are using NG.

Unknown

Oh they do work,

but I had to use much much smaller than 5/16" to get it quiet. It was pretty-much "trial & error" for each bank as one would affect the other,,, time consuming, given what I have.