Fire Tube Boiler Deposits

Scotty13

I sure hope someone can help our facility solve an expensive issue we've had with one of our 100PSI steam boilers for 7 years. We have 4 steam boilers all fed with the same feed water and treated with the same chemical batch ( including Amine and Oxygen Scavenger). 3 have rarely if ever blown tubes. One has blown multiple and always shows deposits on the tubes. It also battles high alkalinity and conductivity. Anyone have theories as to how this can happen? Thank you.

Big Ed_4

I would recommend posting for what process the boilers are being used for and the modulation controls being used if any....

SlamDunk

Theory- A manufacturing defect? Auto surface blowdown valve not working?

Scotty13

They are used for preconditions room humidification and building heat. We returned the whole boiler 2 years ago thinking maybe it was a bad batch. But we are seeing heavy deposits already. We blow down manually every day. Working on automated blowdown. Unsure why the same blow down .ethod works for the other 3 boilers without issue.

SlamDunk

Do they all run simultaneously? Do they rotate? Or is suspect boiler run more?

Scotty13

2 are 10 PSI and alternate lead/lag daily. The trouble boiler and the 4th are twin 100PSI boilers and alternate lead/lag weekly. So they run equally.

SlamDunk

Sorry, I'm drawing a blank. How well do your low P boilers handle the high pressure feed?

Scotty13

The low pressure boilers are on a separate header.

Scotty13

The trouble boiler also seems to experience high conductivity which can cause deposits from what I understand.  We generally need to blow this boiler down excessively to control it. Not sure what may cause that in 1 of 4 boilers.

EBEBRATT-Ed

Sounds like a job for a good water treatment guy. They are hard to find

retiredguy

How much fresh water do these boilers use and what is the water's source, who is the boiler mfg, what is the size or capacity of these boilers, do you perform water tests daily and if you do what tests do you perform, and where in this country are you located? Can you post a few pictures of the troubled boiler and piping?

motoguy128

Take a really close look at the feed water piping maybe for some reason the trouble Boiler gets all the condensate and less fresh water.  

SlamDunk

Lowering conductivity is best dealt with auto surface blow downs. Bottom blowdowns don't remove particulates higher up in the boiler. With bottom blowdowns you add far more fresh water to the system than you would with surface blow downs. Let us know what you find. This is interesting.

PMJ

You say that all four boilers get exactly the same treatment. Is this confirmed by regular testing of water from each boiler separately by your chemical supplier? They should be doing this monthly at a minimum and they should be supplying separate reports for each boiler. When there is trouble it should be done much more often than that.

I would be confirming for sure that the chemical levels IN EACH BOILER are in fact identical before doing anything else. There must be multiple pumped condensate return tanks feeding the boilers separately and therefore multiple chemical entry points. It would seem possible that all is not actually equal in the boilers.

Confirm that first with actual test reports and go from there.

One other question. What is the actual failure mode of the tubes? What do they look like when removed? What do you mean by a "blown tube"? Holes from oxygen pits? Tubes with those look like they have barnacles here and there but are mostly smooth. Failure all the way through under a barnacle looks like someone took a small drill to the tube. I am wondering if what you mean by "deposits" are actually barnacles and not mineral scale or excess chemical deposits which would be relatively smooth over the entire surface of the tube.

dopey27177

Is the chemical treatment done by installing chemical in the boiler feed tank?

To properly treat a boiler with chemicals the chemicals must be installed in each boiler individually.

Each boiler must be tested t no less than a weekly inspection. The chemicals are then installed via a chemical bottle on each boiler.

See Attachment

Jake

HVACNUT

At the risk of sounding like a complete moron, could it be a grounding issue?

SlamDunk

Very unlikely with boiler controls that require grounds. Not to mention being bolted to the floor and connected to the same pipes as other boiler. It is sounding like a manufacturing issue to me. Maybe it was built on a friday afternoon or a monday morning. Sometimes welding slag on the waterside of fire tubes rot and look like deposits. But OP said they returned the whole boiler two years ago. Not sure if that meant they replaced all the tubes or literally sent the boiler back to manufacturer. But bottom blow downs to lower conductivity every day and rotating weekly doesn't sound like a good plan.

retiredguy

Depending on the size of your boiler system, you may want to consider a good deaerator to remove the carbon dioxide and oxygen from your condensate and feed water.