Feedwater first:
Sand-filtered raw water (breakwater) is heated to around 27 degrees before going through a two parallel Continuous Membrane Filters (CMF), then two parallel Reverse Osmosis (RO) filters. The Feedwater is then demineralised and polished through a set of Electrodeionization Industrial (EDI) and Continuous Electrodeionization Industrial (CDI) units. This is our Demin water. This is treated with Amine (corrosion control) and Eliminox (trade name Orica oxygen scavenger) post Free Flow Falling Film deaeration. This is now Feedwater, stored at about 125 degrees @ 3.4 bar(g).
Economisers are radiant heaters in the flue gas path that preheat the water prior to its entry into the Steam Generating Section of the machine. Steam Generating Sections for a Firetube boiler would be the drum, in a Watertube boiler that would be the Wall Tubes and Boiler Bank.
Inside the Generating Section, Phosphate (PO4) is applied for pH control of around 8.8 - 9.0. PO4 should be kept below 6ppm as higher concentrations can floculate and lead to pluggage.
Saturated steam @ 100 psi: 164 degrees C @ 700kJ/kg. For those of us born after the Metric Conversion Act was passed in 1970 that's about 6.8 bar(g).
As for Superheater rupture at such low pressure, due to the low temperature used as soon as the steam exits the fissure it will desuperheat due to the delta P between the boiler and the atmosphere. You might get a nasty scald (if you're not wearing appropriate PPE) but it won't cut your arm off or anything.
Steam trains and other non Reversing light stuff :)
I was thinking Pete, a good start on a loco would be supply Amine to the Feedwater Tank and use a particle filter (like an inline fuel filter) on the Feedwater Line. Additionally, a small supply of steam bubbling through the Feedwater Tank would aid in Deaeration.
Monster Subaru sold to a good home!! Still a Subaru owner. Will try stay in the Ausubaru loop. Sorry 
Hmm, my chemistry is patchy at best, so apologies for stupid questions.
How does the Amine reduce corrosion ? Is the corrosion related to acidity ? I know the guy with the excellent boiler runs his boiler significalty alkaline. I don't know the specifics though.
How does a steam bleed de-oxygenate the tender ? Curious to understand the physics. I don't know how significant a change it would make to the loco's running injectors. As the injectors when running well tend to 'chirp' and suck in air. Quite a plesant and distinctive sound actually ( means there is water going into the boiler
, sometimes it can be a real struggle with difficult injectors )
At the end or a run day, the boilers are allowed to cool down to 40 PSI then blown down through all available foundation ring ball valves. This usually takes any suspended solids with it if the blowdowns are of a sufficent size. Quite spectacular, but really have to be careful who is around, and ear muffs are preferred. It is an interesting display to dump 25 litres of boiling water through 4x 3/8 ball valves in around 20 seconds.
How does the Amine reduce corrosion ? Is the corrosion related to acidity ? I know the guy with the excellent boiler runs his boiler significalty alkaline. I don't know the specifics though.
How does a steam bleed de-oxygenate the tender ? Curious to understand the physics. I don't know how significant a change it would make to the loco's running injectors. As the injectors when running well tend to 'chirp' and suck in air. Quite a plesant and distinctive sound actually ( means there is water going into the boiler
, sometimes it can be a real struggle with difficult injectors ) At the end or a run day, the boilers are allowed to cool down to 40 PSI then blown down through all available foundation ring ball valves. This usually takes any suspended solids with it if the blowdowns are of a sufficent size. Quite spectacular, but really have to be careful who is around, and ear muffs are preferred. It is an interesting display to dump 25 litres of boiling water through 4x 3/8 ball valves in around 20 seconds.
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Suby Wan Kenobi
- General Member
- Posts: 1914
- Joined: Tue Oct 04, 2005 10:00 am
- Location: Sunny Godwin Beach Qld
Just my 2 cents on boilers, i have worked locomotive, briggs and water tube boilers in many different situations the water tube in a 71/4 guage 2-6-0 was indeed different at was a pig to steam, but hey the boiler was made in the 30s. In model locomotive i found the Briggs to be very good in larger scale 71/4 narrow guage and larger as they steamed well and ran very nicely in both superheated and non superheated compared to a loco type in similar setup and yes the difference is very noticable in performance and ecconomy. the loco type (wetback) in 5in guage works very well as you basically fill the boiler set the feed pump throw in a huge amount of fuel and buzz around a track (on club running days) checking the water level as you can.
I am currently building a NSWGR 38 class in 5 in guage and this will be my first large copper boiler i am going to make , have made a heap of the small donkey engine feed boilers.
I am currently building a NSWGR 38 class in 5 in guage and this will be my first large copper boiler i am going to make , have made a heap of the small donkey engine feed boilers.
Phase-to-Phase Deaeration:
Henry's Law states gas solubility in a solution decreases as the gas partial pressure above the solution decreases - raise the pressure of the tank, push all the dissolved gasses out. As we know, temperature and pressure are mutually dependant, so Henry has also shown us that solubility increases with temperature.
The second aspect of Phase-to-Phase Deaeration is the mechanical scrubbing action of the steam bubbles through the Tender - this is a pretty simple phase-to-phase scrubber whereby dissolved gasses in the liquid phase are carried over into the vapour phase, thereby removed from the Tender with the vapour through a vent.
Without going into too much depth unnecessarily (but I'd love you want!), dissolved O2 rusts iron as under the pressure of the boiler the oxygen precipitates (remember Henry?) and forms bubbles on the walls. Precipitation of CO2 forms Carbonic Acid bubbles which then reacts with the H2O to also rust the iron.
I should have said this earlier sorry: Amine dosed to Feedwater as it is carried over with the steam into the Superheaters, process and condensate, maintaining corrosion protection where it is most critical in terms of vessel failure.
Phosphate is not necessary to be used in such a small boiler for pH control, especially due to the waste steam system on the locomotive. As you blow down at the end of each shift, PO4 retention isn't an issue.
I would recommend keeping the pH value above 8.0 (for the protection of the Iron) and below 9.0 (for the protection of the Copper).
When it comes to chemical Feedwater treatment, the best people to talk to are NALCO. You could probably arrange a delivery of suitable chemical as well as a dosing strategy with them over the phone after a couple of emails. In fact I work quite closely with a Nalco rep and I'll ask him on Monday what he would recommend.
Henry's Law states gas solubility in a solution decreases as the gas partial pressure above the solution decreases - raise the pressure of the tank, push all the dissolved gasses out. As we know, temperature and pressure are mutually dependant, so Henry has also shown us that solubility increases with temperature.
The second aspect of Phase-to-Phase Deaeration is the mechanical scrubbing action of the steam bubbles through the Tender - this is a pretty simple phase-to-phase scrubber whereby dissolved gasses in the liquid phase are carried over into the vapour phase, thereby removed from the Tender with the vapour through a vent.
Without going into too much depth unnecessarily (but I'd love you want!), dissolved O2 rusts iron as under the pressure of the boiler the oxygen precipitates (remember Henry?) and forms bubbles on the walls. Precipitation of CO2 forms Carbonic Acid bubbles which then reacts with the H2O to also rust the iron.
I should have said this earlier sorry: Amine dosed to Feedwater as it is carried over with the steam into the Superheaters, process and condensate, maintaining corrosion protection where it is most critical in terms of vessel failure.
Phosphate is not necessary to be used in such a small boiler for pH control, especially due to the waste steam system on the locomotive. As you blow down at the end of each shift, PO4 retention isn't an issue.
I would recommend keeping the pH value above 8.0 (for the protection of the Iron) and below 9.0 (for the protection of the Copper).
When it comes to chemical Feedwater treatment, the best people to talk to are NALCO. You could probably arrange a delivery of suitable chemical as well as a dosing strategy with them over the phone after a couple of emails. In fact I work quite closely with a Nalco rep and I'll ask him on Monday what he would recommend.
Monster Subaru sold to a good home!! Still a Subaru owner. Will try stay in the Ausubaru loop. Sorry
Ok. My friendly local Nalco water treatment rep reckons he can get a tanin solution that would be a perfect pH/corrosion/dissolved gas control for that sized boiler.
Dosage is a simple slug dosage every so often during the day, he said water quality is easy to manage - if it looks like tea then you're right as rain.
He'll get a cost for me tomorrow.
Dosage is a simple slug dosage every so often during the day, he said water quality is easy to manage - if it looks like tea then you're right as rain.
He'll get a cost for me tomorrow.
Monster Subaru sold to a good home!! Still a Subaru owner. Will try stay in the Ausubaru loop. Sorry
Mudrat, would you mind floating the name 'Maxitreat 450' past your nalco contact. I am interested in his opinion as that is the treatment recommended to one of our members by a DLI inspector about 15 years ago and his boiler looks near new inside. Granted he also nitrogen purges after every run which has probably made the biggest difference. Your thoughts ?