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Can I use an orifice plate in finned steam convectors?

I'm in my first heating system in a 1936 home with its original 2-pipe steam wet return boiler. American Radiator is the brand. It all works amazingly well but I'm quite sure some or all of the steam traps are failed in the open position. I replaced two of them and they are working. Instead of doing that on the other 20 radiators could I install orifices in the inlet valves? I'm afraid the fin tube heating units might be too small for that solution. I'll attach a photo of a typical unit.


  • Jamie Hall
    Jamie Hall Member Posts: 23,635
    You could use orifices... but it's much easier and more reliable in most systems just to repair the traps (there's no need to replace them -- it's rare to find a trap for which repair parts are not available). Orifices, to function reliably, must be used with a rather restricted and very low pressure range for the steam feed -- typically on the order of a few ounces per square inch maximum or, alternatively used where the steam feed pressure can be controlled within a very narrow pressure band.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
    EBEBRATT-Ed Member Posts: 15,829
    If it was me I would change the guts in the other traps. That was the way that system is designed to run.
  • piano_plumber
    piano_plumber Member Posts: 4
    Thanks very much for the help. I have found replacement parts for my old traps but its been impossible to get the tops off. I was afraid of breaking a pipe or the convector with too much force. Even after I removed and replaced them I couldn't get the old ones open using a workbench vise and hefty wrenches. I understand the steam traps well and not much about the orifice method so I'll follow your suggestions.
  • piano_plumber
    piano_plumber Member Posts: 4
    Sorry, I meant "first heating season" up there in my first post.
    JUGHNE Member Posts: 11,102
    The orifices would work well if your boiler can operate at a fairly steady pressure less than 2 PSI. And if you are somewhat over radiated because the orifice method usually would only give you 80% of the max heat available from the emitter.

    If you want to go for the trap repair, IIWM, I would remove the convector via the unions at each end.
    Then with an impact driver and the correct 6 point socket the tops come off easily. Use a pipe wrench on the body for back up to prevent any riser pipe damage.
    That would be a good time to take the fin tube outside for cleaning also.
  • retiredguy
    retiredguy Member Posts: 929
    Show us a picture of the old traps and we will explain just what tools to use to repair them and how to do it, or just follow @JUGHNE advice and remove the convector.
  • The Steam Whisperer
    The Steam Whisperer Member Posts: 1,219
    We use Orifices nearly exclusively when faced with systems with radiator traps. Typically you can size them for very low pressure drops ( like 8 ounces) and often eliminate the condensate pump. This is especially the case for former naturally induced vapor vacuum systems that originally had no condensate pump. If sized for a higher pressure drop, like 2 to 3 PSI, you can use a modulating boiler with outdoor reset so in warm weather very low pressures are produced causing only a small portion of the element to heat and in colder weather gradually turning up the heat source to warm more of the heating element. With the higher pressure drops, you can get some slight noise in colder weather. Most of the time, however, orifices even designed for 2 to 3 psi drop on design days will only be running 8 to 10 ounces on a typical winter day. The other nice thing I have found is that for most vacuum systems, you can eliminate the vacuum pump too, since the orifices help ensure even delivery of steam to the radiators and, you can effectively downsize the radiators ( since they are almost always quite oversized) to the smaller piping found in vacuum pump system. The only place where they are limited is in convectors with air dampers or on systems that need the full capacity of the. heating elements. However, even on these systems using an outdoor reset control you will benefit most of the year because the steam will rarely reach the steam trap, giving you much longer trap life.
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  • JoshP
    JoshP Member Posts: 72
    I used a small propane torch to heat the housing up some then a cordless 1/2” drive impact wrench with appropriate size socket to get the caps off my traps.They probably haven’t been off since 1928 .
  • piano_plumber
    piano_plumber Member Posts: 4
    Thanks, I'll try the impact wrench. I did manage to open one with a big pipe wrench and a big vise, but it wrecked the cap. Luckily I bought a couple new ones just in case.
  • dopey27177
    dopey27177 Member Posts: 887
    if you are repairing them on the bench, try this.
    With a torch heat the outer body of the trap then with a cold wet rag coll the cap of the trap then let stand till you can handle the trap.

    The outer body of the trap is a thinner metal than the cap, therefore it will expand more than the cap. By cooling the cap first the cap will shrink a bit. The aged heated seal should be broken and the cap should be able to be removed.