Equalizer and near-boiler piping

ethicalpaul

Intplm. said:

@ethicalpaul

Have you ever looked into the Hartford Steam Boiler Insurance Company?
Im not sure if they are a steam boiler insurers still, but they have shown expertise in steam and steam heating concerns for more then one hundred and fifty years.
They started when steam power was in its infancy and they implemented many steam heat and steam energy safety requirements.
You might enjoy their history.
Looking into them you might find some of the answers as to why things are done the way they are to this very day.
It might be worth a look?

I have looked into them a little bit. I don't hold them in very high regard because the "hartford loop" is basically useless and I don't believe it ever prevented any significant number of boiler explosions.

Intplm.

Not the point Im making surely.
Was asking if you have looked into them or would like too.. They are a company with a vast history and might be worth your while.
You seem to enjoy the steam discussions very much and thought you would like there story.

JUGHNE

Paul, there is a lot of history for the HL.
When introduced, boilers held a lot more water and could perhaps fire longer before going dry.

No auto shut offs, only damper the fire and then drag the coal out onto the floor.

But if you wanted their insurance you would have the Hartford Loop on your boiler.

They are a money company and it was in their interest to not pay out for boiler explosions.
So the Loop must have been effective, they got no commision for each HL installed.

Many boilers with pumped returns have a HL, in addition to a check valve in the feeder line, this would prevent the boiler from draining out if a failure of the feeder lines/pump piping occured.

It would be interesting to see the numbers from the past, of a drop in explosions after the requirement.

Intplm.

ethicalpaul said:

Intplm. said:

@ethicalpaul

Have you ever looked into the Hartford Steam Boiler Insurance Company?
Im not sure if they are a steam boiler insurers still, but they have shown expertise in steam and steam heating concerns for more then one hundred and fifty years.
They started when steam power was in its infancy and they implemented many steam heat and steam energy safety requirements.
You might enjoy their history.
Looking into them you might find some of the answers as to why things are done the way they are to this very day.
It might be worth a look?

I have looked into them a little bit. I don't hold them in very high regard because the "hartford loop" is basically useless and I don't believe it ever prevented any significant number of boiler explosions.

I agree to some extent about the hartford loop. But this insurer is very reputable. Held in the highest regard. Give them another look. Maybe look a little deeper than the hartford loop subject. You might find some answers too some of the questions that are not answered here.

ethicalpaul

I'm even a little curious about what kind of explosions the hartford loop was even supposed to prevent on its best day.

Was it systems where a dry fire would turn a boiler red hot and then a lot of water would be introduced?

Barring that, it seems like such a solution in search of a problem. A boiler had to be in service long enough for the wet return to rust out before the HL could even help at all.

neilc

back in the day the tender needed to pee, or eat, or nap,
if that boiler leaked then, the loop would hold back a bit, hopefully long enough that the tender could correct said bad situation, or pull the coals as said above,
that's my take

Waher

One thing I've never understood with modern 15psi steam relief valves is why they aren't required to be wired to some sort of control that will shut off the burner if activated. Unless someone has a Firomatic/ thermal switch installed above their boiler to cut the power (required by some state plumbing codes like Massachusetts), the relief valve isn't going to shut off the boiler until the LWCO engages. That's potentially deadly to someone trapped in a confined space with 212f steam.

Then again I've never understood why so much boiler trim is supplied with iron pipe instead of brass from the factory because the price difference for competitiveness is miniscule. Ditto for why Honeywell insists on making steam pressuretrols that exceed a 2 PSI maximum when the Carbon Club came up with that residential design standard should not exceed 2 PSI 120+ years ago.

JUGHNE

A 15 PSI relief valve with a microswitch to cut off the burner is just another safety for some hack to jumper.

There is already a burner cutoff in the form of the pressure control. Many installs require 2 or more of them.

They too can be jumped as needed.

ChrisJ

JUGHNE said:

A 15 PSI relief valve with a microswitch to cut off the burner is just another safety for some hack to jumper. There is already a burner cutoff in the form of the pressure control. Many installs require 2 or more of them. They too can be jumped as needed.

With all due respect that's like saying we shouldn't have rollout or spill switches because some hack could jumper them.

ethicalpaul

neilc said:

back in the day the tender needed to pee, or eat, or nap,
if that boiler leaked then, the loop would hold back a bit, hopefully long enough that the tender could correct said bad situation, or pull the coals as said above,
that's my take

Yes the catastrophic wet return leaks must all have happened while the tender was leaking

The odds of this coincidence would be astronomical.

But even so, how would that cause an explosion?

neilc

so he avoids getting caught napping, with no heat in the building, and throws water at it,
bad kaboom

Intplm.

neilc said:

so he avoids getting caught napping, with no heat in the building, and throws water at it,
bad kaboom

And the boiler flies through the air landing sometimes blocks away.

ethicalpaul

Seems like word would spread not to do that

Sylvain

Ideally, safety and control should be independant.
Pressuretrol is control.
Safety valve is, as its name implies, safety.

In that line of thought, the pressuretrol controling pressure and the pressuretrol limit controller (the one which needs a manual reset) if it is installed, should be on separate pigtails to avoid one common mode of failure.
It would be even better if it was using another technology or at least another brand.
Safety devices should need a manual reset.
Altough, for the safety of the people in the boiler room, there is merit in the safety valve closing without a reset.

Waher

ethicalpaul said:

Seems like word would spread not to do that

America has always had a problem with substance abuse. At the time choices were limited to tobacco, alcohol, and opium. Alcohol was the cheapest, most readily available, and relatively socially acceptable vice, so it wasn't uncommon for a building's live-in custodian or boiler stoker to be hung over or piss drunk resulting in a negligent ka-boom in the coal fired steam era. They'd add water to a nearly dry boiler, or add too much coal so they could pass out/take a nap/get heat back into the building after they didn't shovel it in all night and the tenants were about to show up for work/school to a boiler without a pressure relief/regulating control and something that's gotta give would give catastrophically.

We are spoiled by natural gas, oil, and electricity being able to be shut off at the flick of a switch to almost immediately stop the production of steam. Coal fires have such a lag time that a mistake made hours ago could be catastrophic with limited to no means to rectify the problem depending on when it is noticed.

The Carbon Club partly organized because people were scared of boilers blowing up on a regular basis and the industry had a financial interest in figuring out uniform safety standards so that the public would feel comfortable buying boilers rather than furnaces.

SteamingatMohawk

Yes, it does not stay steam at elevated temperature for a long time until/if there is enough to fill the entire room. I won't try to calculate the heat transfer rate of cooling that steam, because there are too many variables.

The point is the amount of steam exiting the relief valve into the room. Maybe a more relatable way of trying to visualize the situation is to calculate the number of CUFT per minute being passed through the valve into the room. That comes out to be 103LB/HR/60 MIN/HR = 1.72 LB/MIN. Then 1.72LB/MIN times 26.8CUFT/LB = 46CUFT/MIN into the room, about equal to the size of a full cord of wood (4FT x 4FT x 3FT = 48CUFT) at that location.

Good comment.

Erin Holohan Haskell

We have a section in our Heating Museum about boiler explosions here with documents from the 1800s.

ethicalpaul

Those were cool, but they were all about steam boilers in power applications like steamboats, or they were about hot water boilers in residences and schools that blew up--those ones seemed to be an insurance sales tool (the ones in the "Locomotive" journal by the Hartford Boiler Insurance people".

None of the information really applied to residential low-pressure steam I'm afraid.

PS: all those guys must have been paid by the word

SteamingatMohawk

Perhaps, better safe than sorry is the answer.

That being said, where in the "system" is the weakest link that would fail first in a pressure excursion (and at what pressure)?

Based on my investigations since joining HH, I have reported that some pressure gauges are designed for 130% of full range structural integrity (I can't state that is true for all). I don't remember offhand what the radiator vents are rated at, but have a vague recollection it isn't very high.

ethicalpaul

I'm not sure what you mean. Are you saying those possible failure points would lead to more or fewer explosions? I don't see how they are related.

SteamingatMohawk

The point is simple, as pressure rises, the weakest component will fail first.

What is the weakest component, the boiler, piping, control/safety devices, radiator vents, pressure gauges (especially low range) or something else?

ChrisJ

SteamingatMohawk said:

The point is simple, as pressure rises, the weakest component will fail first.

What is the weakest component, the boiler, piping, control/safety devices, radiator vents, pressure gauges (especially low range) or something else?

Magnehelics have a rubber plug that blows out at 25 PSIG.


The point I'm getting from this discussion is a properly sized steam boiler can easily prevent explosions.