Water Gauges for Boilers.

[terryd]

Hi,

I cannot see for looking it was there!

Hi J.Andrew,

.........................


I also like your tangential tool holder. That's on my projects list.

Mine is an Australian made Diamond Tool holder which are made in both RH & LH in several sizes. I am very happy with it and rarely use any other tool...............

Hi Tony/Andrew,

Just out of intrest I have a mid 19thC (around 1860 ish) workshop .practice book showing two examples of these 'Diamond' type tangential cutting tools. Just goes to show that there is little new in the world of manufacturing until you get major technological shift such as NC and computer control.

TerryD

 

[Steamchick]

Tony, do you forsee any problems with dezincification of the brass which is in contact with the boiler water? Most commercially made ones and designs for making your own tend to specify bronze or GM and is what I have used on ones I have made in the past along with other boiler fittings such as clacks, blowdowns, plugs, etc.

J

Hi Jason. A good question about de-zincification:
I think it depends on the specific grade of brass, as to how long it can last when permanently wetted. Also, the combination of metals in the proximity of the water (acting as an electrolyte) will cause the "highest electro-potential" metal to be sacrificed first (The highest concentration of zinc). The recommendation is to use Bronze (zinc free) for all silver soldered bushes, and fittings that screw into those bushes, then brass can be used on anything that is readily replaceable, such as the water gauge fittings away from the bronze joint at the boiler.
I use "snow" water, rainwater or the ice-water when I defrost a freezer, which is probably almost pure distilled water, so is relatively corrosive as an electrolyte for any mixed-metal container. But I have no scale in my boilers.
The real key to safety is an annual inspection, checking everything each time before firing, and when at pressure (Drop the fire if steam leaks have developed! - before a fitting blows apart with disastrous steam expulsion!). And drain after EVERY use of a boiler. (Dry metal doesn't corrode significantly).
Hope this helps.
K2

 

[terryd]

Hi Jason. A good question about de-zincification:
I think it depends on the specific grade of brass, as to how long it can last when permanently wetted. Also, the combination of metals in the proximity of the water (acting as an electrolyte) will cause the "highest electro-potential" metal to be sacrificed first (The highest concentration of zinc). The recommendation is to use Bronze (zinc free) for all silver soldered bushes, and fittings that screw into those bushes, then brass can be used on anything that is readily replaceable, such as the water gauge fittings away from the bronze joint at the boiler.
I use "snow" water, rainwater or the ice-water when I defrost a freezer, which is probably almost pure distilled water, so is relatively corrosive as an electrolyte for any mixed-metal container. But I have no scale in my boilers.
The real key to safety is an annual inspection, checking everything each time before firing, and when at pressure (Drop the fire if steam leaks have developed! - before a fitting blows apart with disastrous steam expulsion!). And drain after EVERY use of a boiler. (Dry metal doesn't corrode significantly).
Hope this helps.
K2

Hi Jason/K2.

Although I build boilers as copper/bronze with replaceable brass fittings I also possess a couple of Mamod locos and a stationary engine of the same pedigree and always wondered how they've got away with brass boilers for so long? A special alloy perhaps but doesnt look any different to most of my sheet brass

Regards

TerryD

 

[terryd]

Hi Jason. A good question about de-zincification:
I think it depends on the specific grade of brass, as to how long it can last when permanently wetted. Also, the combination of metals in the proximity of the water (acting as an electrolyte) will cause the "highest electro-potential" metal to be sacrificed first (The highest concentration of zinc). The recommendation is to use Bronze (zinc free) for all silver soldered bushes, and fittings that screw into those bushes, then brass can be used on anything that is readily replaceable, such as the water gauge fittings away from the bronze joint at the boiler.
I use "snow" water, rainwater or the ice-water when I defrost a freezer, which is probably almost pure distilled water, so is relatively corrosive as an electrolyte for any mixed-metal container. But I have no scale in my boilers.
The real key to safety is an annual inspection, checking everything each time before firing, and when at pressure (Drop the fire if steam leaks have developed! - before a fitting blows apart with disastrous steam expulsion!). And drain after EVERY use of a boiler. (Dry metal doesn't corrode significantly).
Hope this helps.
K2

HiK2,

I thought, from schoolboy chemistry that water without any pollutants i.e. pure water is not a conductor of electricity so not sure how it stimulates a galvanic reaction between dissimilar metals. Of course rai/snow water isn't pure as it picks up contaminants from the air becoming acidic, either dilute sulphuric or carbonic, possibly both, as well as dust and soot particles which helps make it conductive. An interesting event was when Alec Rose circumnavigated the globe in his yawl Lively Lady and had to stop in New Zealand reportedly to repair a 'broken mast' the problem actually was that he had stinless steel fittings on an aluminium mast and the salt sea water cause galvanic corrosion,. In NZ he had mild steel ( may have been forged) fittings to replace the stainless ones and the problem was solved.
When I was teaching, in basic materials science I used to demonstrate the corrosion of stainless by mounting a small piecre of stainless steel sheet and used a rubber band around the assembly to hold the steel in the wood and left it hanging in a strongish salt solution over a weekend, by mondauy morning the band had caused a groove about 10 mm deep into the steel. The idea was to show how stainless steel body parts on a car canbe prone to corrosionunder pressure (tight bolt?) in a salty environment WInter roads). The pupils were mos impressed tha a rubber band could cut stailnless steel

Regards
TerryD

 

[Steamchick]

Hi Terry,
One of the curiosities of chemistry is that distilled water PH 7 acts like a mild acid with dissimilar metals re: electrolytic corrosion. I checked it on Wikipedia (if you believe that?) on a different thread.
I am not a chemist, so can't explain it. But it may be something to do with electro-potential of hydrogen ions versus some metal ions?

K2

 

[Steamchick]

Hi again Terry.
On Mamod brass boilers... I can only guess that if all the brass is the same grade, with no other metals present, then there is no electro-potential to develop de-zincification?
K2

 

[terryd]

Hi Terry,
One of the curiosities of chemistry is that distilled water PH 7 acts like a mild acid with dissimilar metals re: electrolytic corrosion. I checked it on Wikipedia (if you believe that?) on a different thread.
I am not a chemist, so can't explain it. But it may be something to do with electro-potential of hydrogen ions versus some metal ions?

K2

Hi K2,

That's interesting, thanks. Do you have the link to the Wikipedia article, my inquisitive nature is taking over

TerryD

 

[terryd]

Hi again Terry.
On Mamod brass boilers... I can only guess that if all the brass is the same grade, with no other metals present, then there is no electro-potential to develop de-zincification?
K2

Hi,

I figured that one out myself, but surely the brass for the fittings and bushes etc would be of different composition than the sheet brass used for the shell as they need different properties for the different manufacturing processes? Too many differences here.

Rgeards
TerryD

 

[Steamchick]

Data sheet - off the web:

https://www.chemicals.co.uk/uploads/documents/44%20-%202654%20-%20SDS11558.pdf

Is Distilled water corrosive? - Answers

Typically no. It does depend on the processing of the water however. If there is post filtering that removes the minerals and leaves it essentially pure H2O, then you have a relatively aggressive solvent. Distillation alone is not capable of producing water pure enough to have this property.

www.answers.com

Why Is Dimineralized Water Corrosive? - Industrial Professionals

Why Is Dimineralized Water Corrosive? - posted in Industrial Professionals: dear all as most DM water tanks/drums that I have ever seen in different industries are made from SS , does anybody know exactly why DM water is Corrosive?

www.cheresources.com

Araboni:

Dimineralized Water is NOT corrosive. Let's agree on that fact. However, contaminated DM water IS corrosive - especially if contaminated with dissolved oxygen or carbon dioxide.

If oxygen is present, you get one form of corrosion: rust (or iron oxidation). If carbon dioxide is present, you get acidic attack on the steel with resulting acid etching of the steel. Both types are corrosive.

If your DM is stripped of all dissolved gases and is truly pure H2O, then you should have no corrosion. It is the contaminants that give problems - not the water.

What is Distilled Water? - Definition from Corrosionpedia

This definition explains the meaning of Distilled Water and why it matters.

www.corrosionpedia.com

Corrosionpedia Explains Distilled Water
Raw water usually contains a number of microscopic contaminants, along with dissolved minerals, such as calcium and iron. These elements can be removed from water through boiling until water changes to steam; this process known as distillation. When the steam is allowed to cool down and condense into liquid, the resulting purified water is called distilled water.

When water is heated in a distiller, any dissolved solids, such as salt, bacteria, calcium or iron, remain solid while the pure water converts to a much lighter steam and is drawn out for condensation. This water should ideally be nothing but hydrogen and oxygen molecules, with a pH level of 7 and no additional gases, minerals or contaminants.

Since the minerals and ions typically found in tap water can be corrosive to internal engine components, distilled water is preferable to tap water for use in automotive cooling systems. Similarly, it is also used in model steam engine boilers and model engines of other types to prevent scale buildup.

Despite its benefits, distilled water is particularly corrosive. With no minerals to give the water pH balance, distilled water acts like a magnet, absorbing chemicals (phthalates and bisphenols) from plastics, nickel from stainless steel, aluminum from aluminum containers, and carbon dioxide from the air.

There is loads of information on the web... these are just a few postings.
I was also taught (by a water expert - supplying "pure water" for a laboratory system) - This water is more corrosive than regular tap water, so DON'T use it in car cooling systems - or anything similar - without corrosion inhibitors. He also tested and approved the water we mixed with Long-Life Coolant - to make the 50% mix for filling new cars. (Up to 1/2 million per year).
The phrase that hits me as obvious... (I'm sure I was taught this in School Chemistry at about the age of 11 or 12?):
"Despite its benefits, distilled water is particularly corrosive. " - Seems to sum it up?
K2

 

[terryd]

.......................

There is loads of information on the web... these are just a few postings.
I was also taught (by a water expert - supplying "pure water" for a laboratory system) - This water is more corrosive than regular tap water, so DON'T use it in car cooling systems - or anything similar - without corrosion inhibitors. He also tested and approved the water we mixed with Long-Life Coolant - to make the 50% mix for filling new cars. (Up to 1/2 million per year).
The phrase that hits me as obvious... (I'm sure I was taught this in School Chemistry at about the age of 11 or 12?):
"Despite its benefits, distilled water is particularly corrosive. " - Seems to sum it up?
K2

Hi K2,
Interesting reading. Having read the documents you posted it seems that it is any pollutants which make it corrosive not the water itself. I would think that CO2 dissolved would be particularly bad as it produces carbonic acid, after all that is the main cause of acid rain along with sulphur dioxide, but the documents only mention corrosion not galvanic action with distillled and DM water. I am not enough of a chemist to understand how Mamod et al get away with brass boilers, perhaps you're correct about them not having dissimilar metals in the construction.
Your referral to car cooling systems reminds me of the problems we had with Triumph Stags in the 70s. The engines suffered terribly from overheating and the water pump was blamed. However it turned out that the engine had a galvanic reaction problem with aluminium cylinder heads and cast iron cylinder block. This caused the narrow waterways of the heads to clog with aluminium sulphate and this in turn obviously prevented water flow. It was mostly caused by owners using water to fill the cooling system without any inhibitor such as is in antifreeze solutions. It was seen as too expensive to use. Mnd you it was also caused by the poor quality of those heads as they were cast by a third party not inhouse as the Stag was rushed into production early, I have see porous castings and some even had the core sand left in the waterways, it was a disaster for BMC.

Regards
TerryD

 

[Drawfiler]

Brass is a mixture not a genuine alloy, ie the crystals of zinc and copper are discrete and not combined, when subjected to a suitable environment the zinc dissolves leaving a copper honeycomb which is structurally weak and leads to component failure.
The other problem is stress corrosion when the component despite being over engineered fails because it stressed while in a corrosive atmosphere. This was discovered in the ‘60s when building fixings made in Manganese bronze failed in city conditions.
The crystalline structure does help us as lead in commercial brass also exists as crystals which shear easily during machining so breaking up the chips and giving lower ductility leading to better finish.
As others say, dont use brass for fittings.

 

[Steamchick]

Thanks Terry, Interesting about the Stag engines... but I know technology has moved on and cores are made from mixes of stuff so tales of cores being full of sand are history.... But I didn't know the corrosion was Aluminium Sulphate. I wonder where the Sulphur came from? I would have guessed Aluminium Carbonate... from dissolved CO2... or perhaps Magnesium or Calcium carbonate dissolved in tap water...? Maybe there was Mag. Sulphate in the tap water?
On conductivity... It is of course the free ions from solutes in water as a solvent that conduct.... I.E. dissolved gases from the air. Snow and rain have a chance to dissolve everything as they form from condensing vapour in clouds... and hang around for some time in the air before dropping on us! I think snow is purer, than rain because the snow crystals form directly from vapour and being solid and so cold at high altitude do not absorb gases radily? - But that is my GUESS!.
Rain on the other hand is melted snow, or simply condensate, that has fallen from a great height and in doing so will absorb air molecules and have a mix of gasses, particularly O2 and CO2 it seems...
I'm learning all the time...
K2

 

[terryd]

Brass is a mixture not a genuine alloy, ie the crystals of zinc and copper are discrete and not combined, when subjected to a suitable environment the zinc dissolves leaving a copper honeycomb which is structurally weak and leads to component failure.
The other problem is stress corrosion when the component despite being over engineered fails because it stressed while in a corrosive atmosphere. This was discovered in the ‘60s when building fixings made in Manganese bronze failed in city conditions.
The crystalline structure does help us as lead in commercial brass also exists as crystals which shear easily during machining so breaking up the chips and giving lower ductility leading to better finish.
As others say, dont use brass for fittings.

Hi Df,

Surely the zinc from brass wouldn't dissolve in neutral water? it is basically insoluble in that condition, like many other metals such as aluminium it form,s in this case, a protective layer of insoluble zinc hydroxide, which has to be stripped away for any corrosion to take place.

The example I gave in an earlier post of the forced stress corrosion of Stainless steel in a suitable environment demonstrated the process.

Ever since I started work as an apprentice engineer in '63 we were always told, as in the modern model engineering that permanent boiler fittings such as bushes shoult not be made of brass but os bronze but it is ok to make removeable fittings from brass as they can be replaced if problems arise. I'm just renovating a Stuart 504 boiler which has been used for at least 50 years, I know it's providence and the brass fittings including those for the sight glass, sitting now in a weak acid bath to clean up are in apparently perfect condition after a great deal of use.

Best regards

TerryD

 

[terryd]

Thanks Terry, Interesting about the Stag engines... but I know technology has moved on and cores are made from mixes of stuff so tales of cores being full of sand are history.... But I didn't know the corrosion was Aluminium Sulphate. I wonder where the Sulphur came from? I would have guessed Aluminium Carbonate... from dissolved CO2... or perhaps Magnesium or Calcium carbonate dissolved in tap water...? Maybe there was Mag. Sulphate in the tap water?
On conductivity... It is of course the free ions from solutes in water as a solvent that conduct.... I.E. dissolved gases from the air. Snow and rain have a chance to dissolve everything as they form from condensing vapour in clouds... and hang around for some time in the air before dropping on us! I think snow is purer, than rain because the snow crystals form directly from vapour and being solid and so cold at high altitude do not absorb gases radily? - But that is my GUESS!.
Rain on the other hand is melted snow, or simply condensate, that has fallen from a great height and in doing so will absorb air molecules and have a mix of gasses, particularly O2 and CO2 it seems...
I'm learning all the time...
K2

Hi K2,

If I'm quick enough to catch any snow, which seems to be a rare occurance these days, I'll carry out some ph tests to prove your theory. However we seem to generally have liitle snow during recent winters, I was employed in Edinburgh from June 21 to june 22 and we only had about 3 days of very light snow during th ewhole winter period, I probably couldn't have collected any without some ground pollution, I don't know what it was like down here in England at that time.

And the Stag thing it probably was Aluminium Carbonate come to think of it, my old mind gets forgetful of facts these days it was many years ago. I've had very little real experience of casting except for simple aluminium greensand casting when I was teaching metalwork and we used to make cored from coarse sand, isinglass and condition them with CO2.

Regrds

TerryD

 

[Bentwings]

Hi Terry,in the automotive world there are coolant ph testers that test the coolants especially on big over the road trucks. I used a few but really did not understand them basically you just adjusted the coolant antifreeze to color a specific range on the chart or flags as they were called Some times adding distilled water some times just plan water or coolant I don’t recall if there was a numeric value . There was little explanation on the instruction as to what you were doing other than balancing the ph level . Big truck radiators and cooling itemsarevprettyvexpensive and often expensive labor wise to replace so it was an important but little understood thing . My big boat was loaded with anodes everywhere many were yearly replaced others were longer lasting this was fresh water boat. I’ve often heard the salt water boaters complaine about coorosion and the need for anode maintenance .
One of the curiosities of chemistry is that distilled water PH 7 acts like a mild acid with dissimilar metals re: electrolytic corrosion. I checked it on Wikipedia (if you believe that?) on a different thread.
I am not a chemist, so can't explain it. But it may be something to do with electro-potential of hydrogen ions versus some metal ions?

K2

 

[Steamchick]

Hi, It seems that Bentwings has attributed the truck cooling system and boat stuff to me, but that is his bit. My bit is just the comment re- "PH". - Just for the record.
But I remember using PH papers and colourant in Chemistry at school, when titrating solutions.
Terry, you are right, I think, about the dissolved gases in distilled water - or de-ionised water - causing corrosion. I reckon you know more chemistry than I!
Drawfiler, Please teach us more metallurgy. This is all new to me. I like to learn "why" things are what they are....
K2

 

[Bentwings]

Hi K2,sorry I didn’t mean to sound rough I was just posting experience . Interesting I worked at international diesel that made Ford 6.0 v 8 diesels. Ultimately Ford had a massive recal of the 6.0 diesel. I think they stopped production entirely for a while . They had about every problem in the book . They had to use special coolant as the diesel produced some kind of harmonics that caused the lower cylinder to crack in the block. Some how the new coolant solved this for a while . Had nothing to do with corrosion . My grand son has one of these now and it’s been a confining source of issues . The radiator being one of them . Salt water boats have problems but fresh water ones do too. In the winter when they are hauled out they are pressure washed to remove algae and invasive groth then we changed anodes and cleaned the props and underwater metals most are stainless steel so more or less non coorosive They don’t use radiators but use heat exchangers these require service and expensive replacements if mufflers are not drained they freeze and split not fun replacing

I liked my Cummins diesel it’s got 450 k on it still runs good no corrosion I put one radiator in it due to cracking road salt is the worst enemy up here in north land

If I'm quick enough to catch any snow, which seems to be a rare occurance these days, I'll carry out some ph tests to prove your theory. However we seem to generally have liitle snow during recent winters, I was employed in Edinburgh from June 21 to june 22 and we only had about 3 days of very light snow during th ewhole winter period, I probably couldn't have collected any without some ground pollution, I don't know what it was like down here in England at that time.

And the Stag thing it probably was Aluminium Carbonate come to think of it, my old mind gets forgetful of facts these days it was many years ago. I've had very little real experience of casting except for simple aluminium greensand casting when I was teaching metalwork and we used to make cored from coarse sand, isinglass and condition them with CO2.

Regrds

TerryD

 

[Bentwings]

the distilled water is interesting I had some and used it in a humidifier thinking it was good . Ruined the humidifier .
Data sheet - off the web:

https://www.chemicals.co.uk/uploads/documents/44%20-%202654%20-%20SDS11558.pdf

Is Distilled water corrosive? - Answers

Typically no. It does depend on the processing of the water however. If there is post filtering that removes the minerals and leaves it essentially pure H2O, then you have a relatively aggressive solvent. Distillation alone is not capable of producing water pure enough to have this property.

www.answers.com

Why Is Dimineralized Water Corrosive? - Industrial Professionals

Why Is Dimineralized Water Corrosive? - posted in Industrial Professionals: dear all as most DM water tanks/drums that I have ever seen in different industries are made from SS , does anybody know exactly why DM water is Corrosive?

www.cheresources.com

Araboni:

Dimineralized Water is NOT corrosive. Let's agree on that fact. However, contaminated DM water IS corrosive - especially if contaminated with dissolved oxygen or carbon dioxide.

If oxygen is present, you get one form of corrosion: rust (or iron oxidation). If carbon dioxide is present, you get acidic attack on the steel with resulting acid etching of the steel. Both types are corrosive.

If your DM is stripped of all dissolved gases and is truly pure H2O, then you should have no corrosion. It is the contaminants that give problems - not the water.

What is Distilled Water? - Definition from Corrosionpedia

This definition explains the meaning of Distilled Water and why it matters.

www.corrosionpedia.com

Corrosionpedia Explains Distilled Water
Raw water usually contains a number of microscopic contaminants, along with dissolved minerals, such as calcium and iron. These elements can be removed from water through boiling until water changes to steam; this process known as distillation. When the steam is allowed to cool down and condense into liquid, the resulting purified water is called distilled water.

When water is heated in a distiller, any dissolved solids, such as salt, bacteria, calcium or iron, remain solid while the pure water converts to a much lighter steam and is drawn out for condensation. This water should ideally be nothing but hydrogen and oxygen molecules, with a pH level of 7 and no additional gases, minerals or contaminants.

Since the minerals and ions typically found in tap water can be corrosive to internal engine components, distilled water is preferable to tap water for use in automotive cooling systems. Similarly, it is also used in model steam engine boilers and model engines of other types to prevent scale buildup.

Despite its benefits, distilled water is particularly corrosive. With no minerals to give the water pH balance, distilled water acts like a magnet, absorbing chemicals (phthalates and bisphenols) from plastics, nickel from stainless steel, aluminum from aluminum containers, and carbon dioxide from the air.

There is loads of information on the web... these are just a few postings.
I was also taught (by a water expert - supplying "pure water" for a laboratory system) - This water is more corrosive than regular tap water, so DON'T use it in car cooling systems - or anything similar - without corrosion inhibitors. He also tested and approved the water we mixed with Long-Life Coolant - to make the 50% mix for filling new cars. (Up to 1/2 million per year).
The phrase that hits me as obvious... (I'm sure I was taught this in School Chemistry at about the age of 11 or 12?):
"Despite its benefits, distilled water is particularly corrosive. " - Seems to sum it up?
K2