is 1/2 fiberglass insulation on steam pipes useless?

bbillcee · November 30

HI guys

I had my boiler replaced a bunch of years ago and had asbestos removed from the steam pipes. i covered most of it with the 1/2 inch stuff from depot but i never did alot of the fittings as well as some full lengths of pipes. i ordered a bunch of stuff to make it a better job then started reading it should be minimum 1 inch….do i need to do everything over??

ethicalpaul · November 30

”Need” is a strong word.

If your basement is still warmer than you’d like it, you can consider 1” thick insulation which will be a better insulator.

But even your 1/2” is way better than nothing

Larry Weingarten · November 30

Hi, I'll ad that I've never seen a law stating that you cannot insulate over the existing insulation. I've installed two layers over some lines to good effect. Energy never really gets cheaper, so why not keep the benefit of what you already have? 🤔

Yours, Larry

CoachBoilermaker · November 30

My 60' single pipe steam main loop is hidden behind drywall. (2.5" diameter)

But, I have a partial 12 foot section that is exposed.

Confused about steam pipe insulation sizing.

I used a tape measure.
My steam main has a circumference of 7.75"
This translates to a diameter of 2.5"

Does this translate to a 2" nominal pipe size?

https://www.buyinsulationproductstore.com/pipe-insulation-sizing-guide/

I want 1" thickness.
Do I order 12 feet of 2"x1" insulation?

ethicalpaul · November 30

I'd focus on getting your boiler checked out by a competent tech!

delcrossv · November 30

https://forum.heatinghelp.com/discussion/comment/1823401#Comment_1823401

Agreed. First things first.

KC_Jones · November 30

https://forum.heatinghelp.com/discussion/comment/1823400#Comment_1823400

No such OD of 2.5”. 2 3/8” is 2” nominal pipe size, which is probably what you have. That’s a very common pipe size.

Here’s a link to the convoluted story on how we ended up here with pipe sizing. Basically the guy that came up with the concept of “standard” sizes chose the sizes his factory was already tooled up for. He did it during war time when people were very agreeable, smart guy, I hate him.

https://www.supplyht.com/articles/89502-the-story-behind-nominal-pipe-size

As a mechanical designer who has to track these sizes accurately I can tell you in general manufacturing and design, pipe sizing is one of the most confusing things I train people on. They just can’t grasp that pipe is nominal and doesn’t actually represent any dimension on the pipe. Another fun fact. Sch 40 is massive overkill for most things it’s used for. We regularly use sch 10 pipe on refrigeration systems at the company I work for, on the condenser and evaporator side. Even sch 10 is more than enough to hold the pressures.

To the OP, as state by others, 1/2” is fine and better than nothing. I have 1”-1.5” on most of my piping, but my returns are bare. I use my basement as a workshop and I’m down there a lot. So that gives me just enough heat to make the basement tolerable, as I’m usually living around. So, insulate for basement temperatures is always my recommendation.

EBEBRATT-Ed · December 1

The limiting factor on steel pipe pressure ratings is the fittings not the pipe. CI fittings are rated @125 lb steam and 250lb steam. Malleable iron fittings ate rated 150lb steam and 300lb steam. I am talking threaded fittings here.

Pressure ratings are a sliding scale based on temperature. In other words, a 150lb malleable fitting may be rated if used on gas or oil where the temperature is normal much higher than its 150# steam rating.

Schedule 40 pipe is frequently used on high pressure steam (with welded fittings) depending on the steam temperature I think it is good for 300-400 degrees at a reasonable pressure

is 1/2 fiberglass insulation on steam pipes useless?

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