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How thick should steam pipe insulation be

SteamheadSteamhead Posts: 9,058Member ✭✭✭
All I have to go by is whether the outside of the insulation feels warm when the steam is up. I don't think I've ever felt warm 1-inch fiberglass.

BP, did the IECC say whether they were referring to low-pressure or high-pressure steam systems? I'd bet on the latter, since unfortunately steam heat in homes is only popular in the States and Canada. Most steam applications elsewhere are commercial, higher-pressure systems.

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Comments

  • Steve GarsonSteve Garson Posts: 191Member
    How thick should steam pipe insulation be

    Just finished my new boiler installation. Weil McLain SGO-4. Now it's time to insulate the pipes. Johns Manville offers fiberglass pipe insulation with thickness range from 1/2-inch to 4-inch. Obviously, it costs more the thicker you go. At some point, there must be a point of diminishing returns.

    Can someone suggest what thickness I should install?
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  • SteamheadSteamhead Posts: 9,058Member ✭✭✭
    I like 1-inch thickness

    that's what the Dead Men used. 1/2-inch is not enough on steam, the outside still feels warm when steam is up.

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  • KenKen Posts: 1,640Member
    Once again...

    Steamhead is right.

    1/2" is better than none - but not by much. 1" is the best bet. Inch and a half is overkill IMHO.

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  • BoilerproBoilerpro Posts: 1,231Member
    International Energy Conservation Code.....

    Calls for 3 inches minimum for steam pipes over 1 1/2 inches and 1 1/2 inches thick for pipes less than 1 1/2 inches diameter. I don't believe I've ever seen it this thick, but it gets you wondering whether 1 inch thick is really enough for a steam pipe that will be giving off heat for the next 100 years. We install R-38 in our attics when the typical winter day temperature difference is only 40F, what R-value should we use when the temperature difference is regularly 150F on the typical winter day? Hmmmmmm?????

    Boilerpro
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  • BoilerproBoilerpro Posts: 1,231Member
    Here's the Info....Steamhead

    > All I have to go by is whether the outside of the

    > insulation feels warm when the steam is up. I

    > don't think I've ever felt warm 1-inch

    > fiberglass.

    >

    > BP, did the IECC say whether they

    > were referring to low-pressure or high-pressure

    > steam systems? I'd bet on the latter, since

    > unfortunately steam heat in homes is only popular

    > in the States and Canada. Most steam applications

    > elsewhere are commercial, higher-pressure

    > systems.

    >

    > _A

    > HREF="http://www.heatinghelp.com/getListed.cfm?id=

    > 157&Step=30"_To Learn More About This

    > Professional, Click Here to Visit Their Ad in

    > "Find A Professional"_/A_



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  • BoilerproBoilerpro Posts: 1,231Member
    Here's the Info....Steamhead

    Section 803.3.7 All piping serving as part of a heating or cooling system shall be thermally insulated in accordance with Table 803.3.7

    Sure doesn't sound like high pressure steam to me. For hot water the thicknesses are 2 inch for pipes over 1 1/2 and 1 inch for pipes under 1 1/2.
    Chilled water 1 1/2inces and 1 inch respectively.

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  • Steve GarsonSteve Garson Posts: 191Member


    I;m surprised how hard it is to find good pipe insulation. I hard found that only Johns Manville makes it, with only one distributor in the state of Massachusetts.
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  • SteamheadSteamhead Posts: 9,058Member ✭✭✭
    There are others

    keep looking. Can't remember names right now, but the last few batches we got were not from J-M.

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  • LurkerLurker Posts: 123Member
    Here are some rough numbers I've collected

    I believe that for a 2-inch pipe full of steam (around 215 degrees), the heat loss per linear foot uninsulated is around 210 BTU/hr (0.875 sqft EDR).

    With 1 inch of insulation, this figure drops to I believe around 40-45. With 2 inches of insulation, I believe it's around 30.

    Thus, adding more insulation from 1 inch to 2 inches helps a lot on percentage terms (drops the heat loss by 25-35%), but on an absolute BTU scale, it's not nearly as big of a deal as that first inch.

    -Michael
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  • BurnedAlotBurnedAlot Posts: 1Member
    insulation thickness

    Just from experience I've been working with 120lb steam for 13 years and 4" pipe down even on 1" pipe 1 inch of insulation isn't enough.  I put 3 inch on my 4 inch pipe and it's still warm to the touch.  Spirax Sarco guys say to put as thick as possible especially if your pushing the system for every BTU.  If it's a new install I really like the mineral wool type 2 inch shields about what 3 inch fiberglass does.  Just sayin. 
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  • Jamie HallJamie Hall Posts: 3,939Member ✭✭✭
    If I look hard enough at this tree...

    then maybe the bear over there won't eat me.



    Which is part of the answer to the apparent practical difficulties with the IECC.



    There are two reasons for insulation on steam pipes (pipes carrying hot or cold fluids which are not affected by phase change have only one reason).  The first is to ensure that as much of the energy content of the fluid gets to the destination as is reasonably possible.  The second is to minimise the amount of phase change in the pipe (that is, condensation of the steam to water in our case).  There is actually a third reason, but it is sort of irrelevant to energy -- high pressure or superheated steam pipes are dangerously hot to the touch!



    Where does that get us?  The IECC is looking solely at the transfer of heat from source to point of use -- the boiler to the radiator.  Or turbine.  Looked at from that standpoint, requiring very large thicknesses of insulation makes environmental sense (whether it makes economic sense or not is another question in entirely; analysis of that question is fascinating but not relevant here!).  With low pressure saturated steam for heating, the phase change is much more important -- and there it is more related to how the resulting condensate can be handled and where the pipe in question is actually located.  If the pipe is located in an otherwise heated space, the energy is not lost.  There is no loss in overall efficiency of the heating plant due to heat loss from the pipe.  There may, however, be significant issues with balancing the system, or with excess condensate causing problems -- which is why one wants to insulate the steam mains in a heating system.



    Looked at from that standpoint, then, in my humble opinion anything over 1" is going to be wild overkill.



    Now if your steam main is running in an otherwise unheated tunnel between buildings, lets say, then yes -- more is going to be better, almost to the silly point!



    For what it's worth...
    Jamie



    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England.



    Hoffman Equipped System (all original except boiler), Weil-McClain 580, 2.75 gph Carlin, Vapourstat 0.5 -- 6.0 ounces per square inch
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