Is the LWCO the most important safety device?

steamfitter

As I read about steam boiler explosions, I often wonder if there are national records that show the most common causes of these explosions. Going back to Holohan's writing about the explosions that occurred as a result of the 1700x expansion of water into steam when watet was added to a dry fired boiler, lends me to think the LWCO as being more important than the PRV or SRV.
Thoughts?
Is it fair to say that a malfunctioning LWCO is more dangerous than a malfunctioning PRV?

gerry gill

well, that may depend on what your present emergency actually is.

EBEBRATT-Ed

safety valve, Low water cutoff and pressure control.

I would put them in that order. Just my opinion

Fred

I'd rate all three equally important. A failed Pressure control can allow pressure to get way out of hand and, under that circumstance, a failed PRV will certainly be critically important. Additionally a dry boiler with a failed LWCO, while pressure won't be an issue, is a critical failure of a different nature.

ChrisJ

I think it depends on the system as well.
For me, the pressuretrol is almost useless as is the pressure relief. The chances of my setup ever needing them is slim, but not non-existent.

LWCO, spill switch and rollout switch are very important to me. I've also considered adding a temperature switch above the boiler as well.

Overall I have to agree with what has been said above.
All of the safeties are equally important. However, spill switches and rollout switches were not mentioned even though on atmospheric boilers they can easily save a life.

steamfitter

Is it true that the pressuretrol is mainly a control and not a safety? Unless there is an additional high limit manual reset pressuretrol added.

Not trying to diminish the importance of the PRV, but are recent steam boiler explosions due to a dry fired boiler caused by a failed LWCO, and a subsequent addition of cold water?

ChrisJ, can you explain a bit about spill and rollout switches? I have little knowledge in the electrical dept. Thank you!

Fred

Pressuretrols are basically a safety device but, where boilers are over-sized, they serve both control and safety functions. PRV's are for safety and act as a back up should the Pressuretrol fail. It may be true that most boiler explosions are caused by a dry fire and the addition on water into a dry boiler but pressure can go awry from a failed Pressuretrol/Vaporstat or a clogged pigtail that doesn't let the Pressuretrol see the boiler pressure. Certainly a manual reset is a good back up, unless it is on the same clogged pigtail. They should always be on a separate pigtail.
Of course, a failed safety on the gas valve or a delayed ignition can be a cause for an explosion as well. I would guess probably more explosions from a fuel issue than dry fire. I'm not sure?? Pilot sensor (thermocoupler or other sensor) and flame sensors are equally critical.
In any case, a PRV is required by all municipal codes so they must be there. I believe the Pressure control device is a code requirement also. Certainly I would not want to attempt to install a boiler without those devices and put someone at risk or their property at risk.

Jamie Hall

Perhaps the confusion over how a pressuretrol or vapourstat should be regarded -- safety device vs. control device -- comes about because in almost all cases the device is being used to turn off the boiler at a low (say 2 psi) to very low (say 6 ounces) pressure, in response to the system demand for steam being less than the ability of the boiler to make steam. This is not a safety function -- rather, it is intended to improve the efficiency of the overall system by modulating the effective firing rate of the boiler to match system demand.

It happens that setting at those pressures also protects some of the devices in the system -- particularly vents and traps -- from damage from higher pressures; generally, however, when these devices fail from higher pressures it is not a safety hazard, although it does degrade the system performance.

If there is only the one pressure control device, and it is set low, it is a bit of a stretch to regard it as a safety device -- and one is left with the pressure relief valve as the sole genuine safety device for overpressure.

I believe that there should be at least two safety devices for each function: low water, high pressure, whatever. Therefore -- there should be two LWCOs and at least two independent pressure controls, since the PRV is a last ditch defence. Further, at least one of the two safety devices of each sort should be manual reset. Pain in the neck if they trip -- but at least it should get somebody to look at the situation and wonder why...

HVACNUT

I think the technician is the most important safety device.
Went to a call at a convent for nuns. The night guy thought he disconnected the in-line draft motor and bypassed all safeties on an 8 section with an F15 Riello. He even went around the switching relay and wired the burner direct. When I got there, I never saw such a pretty glow.
We had to replace 4 sections.

ChrisJ

steamfitter said:

Is it true that the pressuretrol is mainly a control and not a safety? Unless there is an additional high limit manual reset pressuretrol added.



Not trying to diminish the importance of the PRV, but are recent steam boiler explosions due to a dry fired boiler caused by a failed LWCO, and a subsequent addition of cold water?



ChrisJ, can you explain a bit about spill and rollout switches? I have little knowledge in the electrical dept. Thank you!

A spill switch gets hot if the flue doesn't vent properly and the drafthood spills into the room. It trips, and shuts the burner off and must be manually reset.

A roll out switch is near the burners and detects if the flame "rolls out" from where it belongs, such as towards wiring etc and shuts the burner off.

PMJ

I'm struggling to picture how the LWCO isn't the most important. No pressure device will tell you about a fire under a dry boiler or help you if water is added to same. Locking out the fire when there is still a lot of water and only a bit low is crucial. When I blow down the LWCO I do it with fire on and let out enough water to see it turn off the burner every time.

ChrisJ

> @PMJ said:
> I'm struggling to picture how the LWCO isn't the most important. No pressure device will tell you about a fire under a dry boiler or help you if water is added to same. Locking out the fire when there is still a lot of water and only a bit low is crucial. When I blow down the LWCO I do it with fire on and let out enough water to see it turn off the burner every time.

If the boiler has plenty of water but is dumping CO into the home while people sleep is the LWCO going to help them?

All of the safeties are equally important as they all serve different purposes.

PMJ

> @ChrisJ said:
> > @PMJ said:
> > I'm struggling to picture how the LWCO isn't the most important. No pressure device will tell you about a fire under a dry boiler or help you if water is added to same. Locking out the fire when there is still a lot of water and only a bit low is crucial. When I blow down the LWCO I do it with fire on and let out enough water to see it turn off the burner every time.
>
> If the boiler has plenty of water but is dumping CO into the home while people sleep is the LWCO going to help them?
>
> All of the safeties are equally important as they all serve different purposes.
>
>

I was under the impression the discussion was about equipment on the boiler, not a general one of all safety equipment in the house.

SlamDunk

Another way to prioritize,

On our high pressure boilers at work, we test primary LWCO and auxiliary LWCO daily. We test pressure relief valves annually and pressuretrols annually.

We replace Primary LWCO float and switches every five years or as necessary, We replace auxiliary LWCO probes annually, pressure relief valves every five years and pressuretrols- well so far, we haven't changed a pressuretrol yet.

So: LWCO, pressure relief valves, pressuretrols.

ChrisJ

PMJ said:

> @ChrisJ said:

> > @PMJ said:

> > I'm struggling to picture how the LWCO isn't the most important. No pressure device will tell you about a fire under a dry boiler or help you if water is added to same. Locking out the fire when there is still a lot of water and only a bit low is crucial. When I blow down the LWCO I do it with fire on and let out enough water to see it turn off the burner every time.

>

> If the boiler has plenty of water but is dumping CO into the home while people sleep is the LWCO going to help them?

>

> All of the safeties are equally important as they all serve different purposes.

>

>



I was under the impression the discussion was about equipment on the boiler, not a general one of all safety equipment in the house.

I was under the impression a spill switch was on the boiler.

PMJ

@ChrisJ

I understand that a spill switch is installed on the boiler. I don't have a spill switch at all which I assume illustrates that I don't agree with you that it is equally important to LWCO. My CO worries are covered by general house safety equipment. I'm guessing I'm not the only one set up this way and by default ranking those two pieces of equipment with respect to importance.

The OP was looking for opinions about ranking importance. I offered an opinion. You have offered an opinion that all devices are of equal importance. It would seem he has from us what he is looking for.

ChrisJ

PMJ said:

@ChrisJ

I understand that a spill switch is installed on the boiler. I don't have a spill switch at all which I assume illustrates that I don't agree with you that it is equally important to LWCO. My CO worries are covered by general house safety equipment. I'm guessing I'm not the only one set up this way and by default ranking those two pieces of equipment with respect to importance.

The OP was looking for opinions about ranking importance. I offered an opinion. You have offered an opinion that all devices are of equal importance. It would seem he has from us what he is looking for.

Agreed.

steamfitter

Thank you all! Interesting and informative. The order of maintenance and replacement mentioned by SlamDunk is enlightening, even though it's on high press boilers.
All in all, safety is always an import subject to discuss. One of my favorites is when Dan H. wrote about how additional devices are required by code on boilers that service a larger building with more occupants. As if the small home with few occupants' lives were not as valuable.
A bit of humor, however, many things come down to costs (especially insurance) and government regulations or maybe the lack of, depending on your point of view.

steamfitter

meant to write ..." important subject," on the last post.

JUGHNE

Insurance companies often dictate/lobby the amount of safety controls needed. As far as high occupancy loads it would be based on the amount of claims they would have to pay out.
They have the best bean counters in the world and know where to draw the profit lines. IMO
So you are statistically safer in a house with only a single LWCO than an apartment building with a single LWCO......thus the apartment is required to have the second LWCO.

steamfitter

Interesting!
makes sense. thanks for that info!

ChrisJ

They are also the reason there are laws regarding seatbelts. Of course you should wear one, but the only reason you are forced to is because of insurance companies.

At least those are the rumors I've heard.

SlamDunk

Another way to think about it is, if you are knowledgeable about steam systems, if you had to take one of the three devices out, which one would it be? That would be the least important

Fred

Another way to look at it is none of them are important 99.99% of the time but that .01% each is critical for safety of home and health. It is "insurance" in another form.

EBEBRATT-Ed

Thinking about the old coal boilers. No pressure control & no low water cut-off didn't need them , there was no wiring.

Some boilers had a fuseable plug in the crown sheet of the boiler. If the water level was low the plug would melt and the remaining water would douse the coal fire.

So, like I said above the safety valve wins!

j a_2

EBEBRATT-Ed said:

Thinking about the old coal boilers. No pressure control & no low water cut-off didn't need them , there was no wiring.

Some boilers had a fuseable plug in the crown sheet of the boiler. If the water level was low the plug would melt and the remaining water would douse the coal fire.

So, like I said above the safety valve wins!

That's interesting....When I was a young kid. I loved sitting in front of my Grandfathers coal boiler and playing with the coals...as they were burning....I also loved the coal deliveries..Back then it wasn't a novelty it was a necessity...And we were city folks

BobC

We were living in a four family house in the early 50's that had 4 steam mummies in the basement - all coal fired. The landlord supplied the coal but the tenants were responsible for stoking and ash removal.

I was 4 or 5 and I can remember my two older brothers struggling to drag the ash barrel out to the curb. I can also remember watching trash trucks going down the street with flames coming out the back from coals that were still hot.

That house is about 500 ft from whee I live now.

Bob

j a_2

Did the mummies have little babies. Lol

BobC

I've wondered if they are still there, some of them last forever. A house across the street had one removed last year without following any procedure I could see. At least they installed baseboard instead of hot air.

Bob

EBEBRATT-Ed

I don't remember much about coal except my grandfathers house was always nice and warm. He burned coal until he died in "72 @ "92" He wouldn't convert to oil.

But I do remember the "ash men". They used to come down the driveway, down the hatchway and take the barrels out to the truck, empty them and then put the barrels back in the celler.

Times have changed!!!!!

steamfitter

Love the personal history!
I grew up in an 8 family, 4 story apartment building in Brooklyn, NY. A large steamer in a huge pit kept us somewhat warm, and the water hammer in the one-pipe steam system always let us know that at least the boiler was firing.
As a teen, I worked in a grocery store a few blocks away which was on the ground floor of a similar building. In the winter, we had to make sure we manually fed the boiler water before we closed the store at 6pm. We stored the paper products in the back room adjacent to the boiler, which I'm sure was where the coal was stored. The path through the boiler room was no wider than 2 ft. because of the boiler pit. I was always a bit nervous carrying the huge 100 roll box of toilet tissue across that path (bridge). If I fell the 3 ft. drop would have hurt and the paper all over that oil fired hot boiler may have been a problem. That paper was heavy, but it built character.

HVACNUT

I'm a few months shy of 50 but you guys really know how to make a guy feel young.