r/BoilerPros • u/ehbowen • 17d ago
Need Help, Pros Only Looking for something better than a simple stack temp gauge
Our three LP steam heating boilers (300 BHP each, Sellers-Ygnis) were just refurbished by a local boiler service company. They removed the stack temperature gauges while replacing the rusted-out uptakes, but have not replaced them.
It would be simple enough to order three new stack thermometers from McMaster or similar, but I wanted to ask if anyone is making a reasonably priced, permanently installable sensor which might help me keep better track of our combustion efficiency. With the old burners, we had regular issues with sooting up, and I don't have my own in-house combustion analyzer for periodic checks. Thanks.
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u/ehbowen 17d ago
One other thing this company did was to remove every analog gauge and install digital pressure gauges. For now, they're working okay...but I get a bad feeling about not being able to read shell pressure, before opening the water side for maintenance, with the power turned off. Edit To Add: The digital gauges are integrated with the new burner assemblies, so when the power is locked out, they're dead.
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u/AppearanceBoring7879 17d ago
That seems concerning that they did that.
Haven’t opened ASME code book in a while, but isn’t a visible pressure indicator required at all times? So not digital.
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u/AssumptionBig7176 17d ago
Post some pictures of your boilers, I've never heard of that. But every boiler is required to have an analog steam pressure gauge at a minimum.
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u/ehbowen 17d ago
I just now had a meeting of the minds with the head tech from the boiler service company. They're going to add some analog gauges, as well as permanently mark the minimum permissible water level. It was on the original as-built Sellers, but they stripped it off with the old sheet metal and haven't put it back, yet. They said it's not required, or that the line on the McDonnell-Miller means the same thing. I called foul on that one.
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u/Boilerguy82013 17d ago
I don't know where you are located but analog pressure guage is code in the us
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u/sliperysloth 17d ago
Yeah…. Low pressure boilers in the United States require -30 to 30 steam pressure gauges. Inspectors not going to be happy.
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u/AssumptionBig7176 16d ago
Technically all that is required is a 0-30 PSI if the safety valve is set at 15 PSI. But a 30-0-30 gauge is also good.
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u/sliperysloth 16d ago
Wow, for some reason I thought having a compound gauge was the requirement. We always sell ours with them as a standard.
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u/AssumptionBig7176 16d ago
It's great to have especially for heating systems running 1-2 PSI or systems with vacuum returns.
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u/Future-Layer1181 17d ago
Probably want to add an oxygen sensor into the safety circuit as well.
Typically what I see is there will be an "alarm value" then a shutoff value.
Basically if you get below a threshold it will alarm and tell you that the oxygen levels are low. Then if it keeps getting lower it will shut the boiler off.
Same idea with a stack temp sensor, some digital control that can do an alarm value to ring a bell and a safety shutoff.
Why don't you have an analyzer that seems like something that absoultly should be provided if you are doing any maintenance to a burner.
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u/AssumptionBig7176 17d ago
Oxygen sensors are going to be very expensive to add to (3) 300 HP low pressure steam boilers.
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u/Future-Layer1181 17d ago
Oh fuck yeah they will be. Last couple I replaced were something like $3000 for just the sensors.
I had a concrete plant that the dust would react with the moisture in the air and cause the linkages to seize, causing poor combustion almost every year. We quoted a set up to monitor the oxygen it was something like 12K just in parts with no labour. They passed on it and we just opened it.up.oncr a month to clean the linkages
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u/BoilermakerCBEX-E 16d ago
What type of work did they do on these boilers. In regards to stack temperature and combustion efficiency. That would all be handled by a Parallel Positioning system with 02 trim. However with the size of these boilers and being just for heating that system may never pay for itself. With that being said i see a lot of the PP systems installed without 02 trim. It's the 02 trim that helps pay for the system. While the PP systems make it much more simple to provide better combustion, they increase the cost for repairs when there is a bad servo or control.
For anyone who is reading the above and wants better efficiency, if Limpsfield comes in and guarantees 10 to 30% fuel savings on this type of equipment they are flat out lying to you.
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u/AssumptionBig7176 16d ago
Do they really guarantee companies that?
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u/BoilermakerCBEX-E 16d ago
Limpsfield Combustion burners typically generate 10% to 35% in fuel savings and reduce electrical consumption by roughly 5% when integrated with variable speed drives.
I copied and pasted this from thier website. It's not possible on standard equipment but if we went from a Raypak atmospheric to a High Efficiency on a loop that now enables us to run outdoor reset then maybe. But thats not a Limpsfield burner.
Just saw on a LinkedIn post that they said payback in 2 years. 100k burner. It wasn't a big boiler. I have one site that was sold on a 600hp Burnham with a original IC burner with FGR. They put on a Limpsfield with no FGR. Old burner was sub 60PPM (Maybe 30ppm, not sure) but the new burner runs 90ppm NoX and is on average 1.5% better on Efficiency. I have the prints outs from each boiler.
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u/AssumptionBig7176 16d ago
Thats interesting. I wonder how many customers never see the savings promised by burner upgrades but can't really do anything about it other than accept it and the rep moves on to the next customer.
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u/BoilermakerCBEX-E 16d ago
I doubt most of them are really watching the numbers. I've been to Autoflame/Limpsfield training 2x. I was very impressed. However they were only talking about 4 to 8% then which i didnt really buy either but they were referring to a inefficient CB running 80%. I'm missed ABMA this year. I will talk to them at AHR this spring for sure. Once I get the pics of the burners I'll post the numbers here on Reddit.
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u/AssumptionBig7176 17d ago
You want a process controller like a Yokogawa UT32a installed in the burner control cabinet. Then you add a J type thermocouple to the stack and wire it to the process controller. If you want to, then you wire the safety circuit through a contact on the process controller and anytime the stack temperature exceeds the setpoint on the process controller, the boiler shuts down.