ROI on adding insulation to steam mains

Steve Garson_2

I am trying to figure out the value of increasing the insulation on my steam mains from the present 1/2-inch fiberglass, to adding an addition 1-inch.

I have 44 feet of accessable mains, so the insulation cost would be around $200. The temp of the insulation now in place is around 95* when the steam is running.

Will added insulation also slow the vacuum that happens when the system cools down after a cycle, causing the occasional "whoosh" inhaling on some of my vents?

Is it worth the money? My gut tells me yes.

Brad White_25

In very rough numbers

Assuming your main size is 2 inches, your pipe -if bare- would lose about 150 BTU's per hour (BTUH) in a 70 degree ambient. Call it 6,600 for the 44 feet you stated.

If steam is within at 2 psig, it would likely be taken down below condensing, naturally until things come to equilibrium (AS-IF!)

With half inch insulation you have, this gets knocked down to about 35 BTUH per foot or 1,540 for the 44 feet.

With one-inch insulation (total) this drops to about 22 BTUH per foot or about 970 for the 44 feet.

Add a full inch on top of the half-inch (1.5 inches total) and the losses drop to about 16 BTUH per foot and 700 or so for the 44 feet. You would save about 800 BTUH when firing if my figuring is correct. About 0.8 lbs. per hour of steam.

This illustrates that the "first inch does most of the work". But it also says that you would cut your present losses about in half. And your present losses are fractional of what bare pipe would be.

In answer to your question, yes, it would slow the vacuum effect. ROI depends on your cost of producing the steam, so that part is up to you.

Steve Garson_2

Brad:

Thanks for the calculations. So if my boiler fires three hours a day, then I am wasting 2.4lbs of steam a day.

Since it takes 970 BTU to generate a pound of steam, with an 85% efficient boiler, it requires 1141 1BTU. So 2.4 lbs requires 2740 BTU per day.

1 gallon of oil = 140,000 BTU divided by 2740 BTU/day = 51 days for a gallon of oil, or around 4 gallons a heating season.

Is my logic faulty? It seems like to little a number.

Brad White_25

85% efficiency on a good day, Steve...

Your logic is about right but the 85% efficiency is more like combustion efficiency. Your actual efficiency on an annualized basis could be less than 65 percent when cycling is taken into account. (Steady State is not a hallmark of steam. By definition it cycles but can serve well between cycles with cast iron radiation.)

So, your savings would be more (your expenditures would be more) if that makes sense.

But the "wasting" is also subjective for the heat "lost" is, one would hope, heating the basement. Not your living space per se, but helps a tad.

Steve Garson_2

So it seems like $200 for the formed fiberglass insulation isn't really worth the money, does it? I'm confused since everyone stressese the importance of the insulation.

Brad White_25

Insulation IS important, Steve

but it is relative to the starting point.

You already have half-inch (AKA half-a**ed) insulation. Better than nothing and knocks the bare-pipe losses down to 1/5th of what they would be.

Starting from bare pipe the goal is to maximize the effort in one bite. If you had bare pipe this would be a no-brainer, go for at least the one-inch or better yet the code-required 1.5 inch thickness if 2" pipe size.

But because you are already more than halfway there, the "law of diminishing returns" kicks in. A fuel cost increase may change your mind.

Point is, do the best you can consistent with good economic princicples and your budget. Throw in some personal encouragement knowing that every BTU lost is permanent. The rest is altruism, your own internal compass.

Personally, I am a long-term thinker.

Steve Garson_2

Brad:

I'm a long term thinker as well. I am going forward with the insulation, primarily to avoid the waste heat in the basement and try to reduce the end of cycle vacuum, where it seems that the radiator vents sometimes open before the main vents.

Thanks for your insights.

Steve

brucewo1b

At 65% Eff over all

That would be about 5 gallons a year @ 2 dollars a gallon 10 dollars a year be twenty year payback less as fuel rises and your eff goes down

B.S.

Tom S.

Cost of insulation...

Steve,

I followed Brad's suggestion and got pipe insulation from Homan's. I got mine in Medford (where I live), but they have a few other locations around Boston.

My cost for 1" fiberglass insulation for 2" pipe was $1.69/ft or about $5.10 per 3 ft section. I can't imagine that 1.5" insulation is more than twice as expensive as 1", but I don't have a price list either.

Worth a phone call anyway, seems like it should be cheaper than $200.

Tom

Brad White_9

Steve, I think

that once the work is done, you will be glad that you did it. Good Luck!

Brad

Christian Egli_2

Just for the whoosh

I don't want to talk you out of the extra insulation, in fact here's one more option: Armacell makes a 300F closed cell foam that is ideal for heat and for banging the head against, plus it beautifies the older insulation.

There is a whoosh?

I am guessing you have Gortons at the main ends? These operate with a bimetallic strip that opens slowly and at a temperature considerably below steam (nothing wrong with the principle though) While most non-Gorton radiator vents open and close on the command of flashing steam - these small holes would open way before any of the Gortons causing the whooshing sounds at the radiators.

Note that with good and even more insulation on your mains, these won't cool much compared to the radiators. This is a very good situation but it means the Gortons won't open for a long time.

Plan 1 most costly

Using vacuum vents or adding check valves between the vents and the system could stop the whooshing returning air. Some care has to be given to how your system would work with vacuum, there may be condensate return issues. Vacuum can be very good and very bad, your luck.

Plan 2

Try using all Gorton vents, mains and radiators. They all operate on the same principle.

Plan 3 least costly

At your end of main add a vacuum breaker or simply a check valve from the main to the atmosphere that lets air rush back in. (Also add a shut off valve for when the check valve needs a time out). I have a picture of this somewhere, if I can only find it.

Brad White_9

Christian- Armacell 300F?

Cool, a new product... I will have to check it out, thanks!

"Head bang protection" is not the least feature I would appreciate, being a tall guy....

Best,
Brad

Steve Garson_2

Tom:

Your posting just saved me 50%!!

Many thanks.

Steve

Steve Garson_2

Christian:

Thanks for your posting. Yes, the main vents are Gortons. You are the first person to raise an alternative solution. What exactly should I ask for at the supply house?

Christian Egli_2

Armaflex HT

http://www.armacell.com/www/armacell/armacell.nsf/ansHTMLSeitenLookUp/USA-TI_Frame?OpenDocument

Have you tried inserting a check valve? Is that working out for you?

Steve Garson_2

I have not had the time to buy a check-valve yet. With the warm weather, it hasn't been a priority. Maybe this weekend.