Buy used boiler ?

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Old 08-29-14, 11:15 AM
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Buy used boiler ?

The boiler in my oil burner is cracked. I see many oil fired boilers for sale on Craig's List. Usually they are just a few years old leftover from gas conversions. Any experience or advice on this?
 
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Old 08-29-14, 11:25 AM
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The boiler in my oil burner is cracked
Did you actually SEE the crack for yourself? Or going on what a salesman told you?

What make/model and age is the old boiler?

In general, used boilers would not be my choice. It's been removed from service, so chances are that no care was taken to prevent damage or rough handling. It's possible to get a bargain, but also easy to get screwed. Caveat Emptor.
 
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Old 08-31-14, 08:09 PM
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I saw the crack. It's a Peerless WBV-03 and 15 years old.
 
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Old 09-01-14, 12:50 AM
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I would never buy a used cast iron boiler, too many chances of leaks or cracks. A steel boiler may be a good buy at no more than 10% of its original cost. You DO need to know what to look at before buying. You need to be able to inspect all the welds and also the tube sheets along with the tubes themselves. You need to be able to tell the difference from a rust stain caused by a leaking tube and a rust stain caused by flue gas condensation. In short, unless you or a trusted friend have experience with boilers I would advise against buying used.
 
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Old 09-02-14, 12:36 AM
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I would, of course, pressure test the boiler before buying--probably with air. I haven't seen any small steel boilers. Who makes them?
 
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Old 09-02-14, 03:35 PM
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Don't!

Never, NEVER, NEVER test a boiler with compressed air, especially a cast iron boiler. Air can be compressed which means it has a LOT of potential energy behind it. A weak cast iron boiler could EXPLODE sending shrapnel quite some distance. The pressure integrity of a boiler is tested by a hydrostatic test but this is NOT a job for a DIYer.
 
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Old 09-02-14, 03:44 PM
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tested by a hydrostatic test
Which means WATER. Because water itself can not be compressed, there is no (or very little, depending on how much air is dissolved in the test water) potential energy stored in the water under pressure.

Read up, do your homework, and understand what POTENTIAL ENERGY is, and NEVER pressure test ANYTHING with AIR!
 
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Old 09-02-14, 05:04 PM
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Pressure testing of fluid systems with compressed air, as has already been said, is very dangerous and shouldn't be done. There was an incident during my navy service - a valve bonnet let go while the fluid system was being tested with compressed air and the packing gland was being adjusted; the valve stem was launched explosively and entered the poor machinist mate's forehead, penetrating well into his skull, killing him instantly. If it had been a proper hydrostatic test, the man probably would have been just startled.

Mechanical systems pressurized with compressed air are potential bombs. Thinking about portable air compressors - I would always pay extra to get an ASME-rated tank, but you won't find them at most big box stores.
 
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Old 09-02-14, 06:04 PM
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While this all might seem a bit off topic, discussing pressure testing with air, it's a SAFETY issue that MUST be stressed... again and again...


Safety at work - Miscellaneous - Compressor explodes, demolishing concrete block wall - Tue Sep 2, 2014
 
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Old 09-02-14, 07:12 PM
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More on Air Compressors

That photo of an air compressor explosion is very graphic. I once visited a plant with a compressor enclosed in steel cage. Why? An earlier compressor had exploded, killing a man, and nobody wanted to work around the replacement compressor unless it was structurally shielded.

I have an older Sears portable compressor which, I regret to say, does not have an ASME tank. If I'm inflating tires, I just set it to, say, 50-60 psi, not higher. And, I consciously try to keep something substantial between me and the tank, but it's not always possible. When I'm through using the compressor, I open the drain valve to depressurize the tank and blow down moisture inside the tank. I'm very afraid of that compressor, and probably should replace it.

If an ASME tank is not better than non-ASME tanks, why are ASME tanks more expensive?
 
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Old 09-02-14, 08:45 PM
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If an ASME tank is not better than non-ASME tanks, why are ASME tanks more expensive?
Paper work.

For a pressure vessel to be given an ASME stamp every little bit of that vessel needs to be documented. That means from the steel mill to the final inspection. All engineering drawings and calculations, the mill where the steel was made, the mill where it was rolled, various laboratory tests, the qualifications of the welders that worked on the vessel along with several inspections culminating with the hydrostatic test. All this paper work is filed with the American Society of Mechanical Engineers, National Board of Pressure Vessel Inspectors, and often also with various state agencies. The inspectors have rigorous training and qualifying exams as well. None of this comes cheaply.

Non-ASME vessels are usually designed to the same standards but they do not have the amount of testing nor are the records of those tests kept by the ASME. The inspections are usually not done by or witnessed by a National Board certified inspector.
 
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Old 09-03-14, 12:21 PM
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I can see that at high pressures. I would think that 2psig or less would be needed to see if the boiler is leaking.
 
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Old 09-03-14, 12:50 PM
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Do as you choose, but don't say we didn't warn you.

I once broke a finger when it was hit by a piece of ice that came flying out of a frozen pipe that was under about 10 PSI of ... yes ... air pressure ... I would not underestimate even the energy that can be contained in 2 PSI of air.

So, what do you intend to do? Pump it up and listen for the 'hisssss' ? Good luck.

If you put a gauge on it, and let it sit, do you think that you will be able to tell the difference between a temperature change and a leak?
 
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Old 09-03-14, 04:30 PM
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Non-ASME vessels are usually designed to the same standards but they do not have the amount of testing nor are the records of those tests kept by the ASME. The inspections are usually not done by or witnessed by a National Board certified inspector.
If it's me standing next to the compressor, I would feel more comfortable if it's an ASME tank. But, at my advanced age, I'm at a much higher risk of dying from many other causes besides being shredded by my exploding portable compressor.

Likewise, hot-water heating boilers. Most are ASME stamped, like my 60-year-old unit - which is maybe why they last so long and seldom, if ever, explode.
 
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