Apartment steam riser, PestBlock foam, and fire

[Ed Brown]

I saw a post similar to mine but it's over 10 years old, so I'm throwing this out again just in case.

I live in an urban apartment building that’s almost 70 years old (1955) and uses steam heat. To mitigate a rodent problem, I sprayed Great Stuff Pestblock to seal off the holes around the steam heat risers. Stupidly, I assumed that foam designed to deter pests would take heat risers into account. Not really. Pestblock has a temperature limit of 240F.

Do I need to worry, or do I remove what I sprayed in (no mean feat)? If the latter, advice would be appreciated. Thanks.

 

[peakbagger]

Unless you have high pressure steam with superheat (extremely unlikely), a low pressure steam system used for heating is probably in the 230F range. Most heating steam boilers are rated at less than 15 PSIG (251 degrees F). My guess is its probably going to shrink a bit.

 

[Ed Brown]

Wow, thanks, it seems I'm in the clear. I think. Since your pay grade is way above mine, can you translate this info about my co-op's boiler?

It's by Superior and was installed in 2012. “A fire-tube boiler, two-pipe up-feed system with vacuum return. Central high-pressure plant 85psi. At each building, steam pressure reduced in a single stage to the five pounds necessary to supply heat to that building’s radiators. Burn either gas or oil to produce a maximum of 60,000 pounds per hour of steam.”

So is the 5psi my key number? Thanks for your previous reply, and double for this.

 

[peakbagger]

Assuming their pressure reducing valves are working correctly and set at 5 PSIG the steam temp of saturated steam will be 227 deg F. The only potential issue is if they are running a bit of superhea in the low pressure heating loop, that is pretty rare in a heating system, not so rare in industry when the desire is to deliver 100% steam to the plant demands versus a mix of mostly steam with some water droplets which is hard on valve seats. So the trick is send it out of the plant with a bit of superheat to make up for heat loss in the pipes so the water droplets do not form. A very rough worst case is saturated 85 PSIG steam is 328 degrees F. If they run 85 PSIG through a pressure reducing valve and do not desuperheat it , the low pressure 5 psig steam could be as hot as 328 deg F. (note there is some theoretical stuff that would make it somewhat lower). Desuperheating steam by spraying water in it increases the volume of low pressure steam that they can send out.

 

[Ed Brown]

OK, so I'll waddle over to the boiler building and ask Guess that's the best way. Thanks for all this info. At least I'll have an idea of what they're talking about (and visa versa), which is a good thing. Thanks a ton, you've been extremely helpful.

 

[EatenByLimestone]

I’d remove it and use flashing/trim coil. Rats will take densely packed exclusion fiber too, but for mice, the flashing is fine.

 

[EatenByLimestone]

I’d remove it and use flashing/trim coil. Rats will take densely packed exclusion fiber too, but for mice, the flashing is fine.

We don’t use foam for anything anymore. It just isn’t reliable enough to attach a warranty to.

 

[peakbagger]

We used to use brillo pads stuffed in crevices to exclude mice.

 

[EatenByLimestone]

That’ll work too. Steel will rust out eventually, stainless or copper is better.

 

[peakbagger]

I think the reason for the use of brillo pads is they are saturated with soap that apparently is repellent to mice so they do not attempts to gnaw it out. I agree that in damp locations a non corrosive wool like stainless would not rust.

 

[EatenByLimestone]

Mice will eat bar soap. No idea if they will try to eat other types of soap.

They will try to eat exclusion fiber too. If it’s not packed dense enough, rats will go through it, lol. That’s incredibly frustrating! The manufacturer of the copper claimed it broke off in their mouth and irritated it. I don’t know if I fully buy that, but most warranty issues I saw was when too little copper was packed into something like a vinyl corner cap and the mouse just went around the side of it.

With mice, silicone alone is sufficient, as long as the hole is completely plugged. If there’s a gap, they will gnaw through it. I believe they follow the air currents.

 

[begreen]

We used to use brillo pads stuffed in crevices to exclude mice.

Yes, I have used coarse steel wool pads for the same purpose in a dry location.