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 Post subject: Re: Best Practice Between Steaming Days
PostPosted: Wed Oct 17, 2018 12:14 am 

Joined: Mon Aug 23, 2004 2:09 pm
Posts: 399
Location: Los Angeles
[quote="Dave"][quote="Jim Baker"]One thing I have wondered about is superheater units. With both wet or dry layup, I'd think there would be condensate in them. Any way to get rid of it? Or is the amount not significant?[/quote]

Pressurize the boiler with compressed air, open the throttle and blow it out.[/quote]

This generally does not work however different boilers may have different results. The problem is that the short necked units will be the first to blow out and then the next row and so on. What happens then is that the compressed air is taking the least path of resistance leaving the longer necked units with maybe up to a gallon of water/ condensate, No mater how many times you charge the boiler the path is open and the air does not need any larger path to empty from. So you have units with oxygen laden water and they will rust and pit from inside.

The best practice is to fill the units with an anti corrosive with oxygen scavenger or a wet
layup.

On the boiler, having air exchange is the best practice, you need to continually move, exchange the air. Placing a couple of small solar powered fans at lower washout holes is one way. The other is to remove the dome cover and place a large fan and leave the lower washout plugs out.

When Santa Fe long termed laid up a boiler they would fill the boiler with water, dump kerosene on top of the water then drain the boiler. The kerosene would coat all of the surfaces. then they left the lower corner washout plugs out.

Santa Fe during washouts would blow out the hot boiler water into a receiving tank. This water would be cleaned and treated for reuse in other engines coming in for washout.


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 Post subject: Re: Best Practice Between Steaming Days
PostPosted: Fri Oct 19, 2018 9:39 am 

Joined: Mon Jan 09, 2017 10:35 am
Posts: 31
First, I am Jim Conte, founder of BoilerSaver. http://www.boilersaver.com

This is posted for the good of the community, not as a " commercial ".

We do not operate as a " for profit '. We never have and never will. We break even.

We do provide ( sell ) what we have found to be the best available products and technology currently available for the historical steam preservation community.

That is 2 % of the equation. The enlightenment of people within this group, making a potentially complex and inter-related group of topics as simple as possible, is the greater and most necessary mission. This is our calling within the realm.

Boiler steel corrodes least when the metal surfaces are conditioned ( passivated ) to a pH between 10 and 12.
This is accomplished by maintaining boiler water chemistry in the 10 to 11 range.
It is not best practice to exceed this, because of the real danger
of Caustic Embrittlement when the pH goes higher.
I prefer to use pH 11 as an upper limit, allowing a safe buffer range.

Oxygen Pitting ( rusting ), is an electro-chemical reaction. By forming a Magnetite Hydroxide protective layer on boiler steel, we hold-off the oxygen attack of the underlying iron. Magnetite Hydroxide is the beneficial effect of maintaining the Basic water chemistry described above. Evidence of this protective layer is a black to grey surface on the steel.

Many previous posters have covered the need to reduce dissolved oxygen exposure to the steel surfaces. Certainly, dry layup is good. Closed dry layup with Nitrogen Inerting and Dessicant is the best possible. I agree that the nitrogen in this case should be applied with the boiler completely dried. Re-usable silica gel dessicant is available at a good electrical supply. I like the dessicant that is blue in the active ( dry ) state and pink in the exhausted state. The nitrogen does not need to be maintained at a high pressure.

I like to use a propane gas regulator. They come pre-set at 11 inches of water, just under 1/2 PSI.
I use a high pressure regulator set for 25 PSI on the supply cylinder and the propane regulator as the second stage.
For safety reason, the boiler should be posted with multiple " Danger - inert atmosphere, ventilate and test for sufficient oxygen prior to entry. " People have died from carelessness here.

Nitrogen from the boiler can be purged through the superheaters.

Wet layup gets trickier. Most of us do not have access to ' Deaerated ' water from an outside source. The water in a steaming boiler that is venting steam is well deaerated, typically less than 40 Parts Per Billion at 220 F and above. The problems arise when the boiler cools and oxygen creeps in. A cooling boiler will pull a vacuum and atmospheric air is drawn in. At 70 F, water will hold 7 Parts per Million of dissolved oxygen. That will pit through the top row of tubes and leave a line of pits at the water line inside the shell in just a few weeks.

Nitrogen blanketing ( inerting ) is wonderful for short-term wet layup, a week to a month. A few extra points nee attention. The connection to the boiler must be above the water level. A small size pipe connection needs to have a manual shutoff at the feed connection. This needs to be backed-up with a boiler pressure rated check valve ained to feed into the boiler. The connection should be metal, sloped down toward the boiler with no liquid traps. If any L.P. steam vapor gets past the check valve, it will condense and return to the boiler without being trapped. Remember, with only 11 inches of water available, each trap reduces the available pressure to cause flow. After the boiler cools to less than 100 F, the nitrogen can be shut off. Simply purge the boiler with nitrogen for 15 minutes per week to maintain the inerting. This is an industrial standard, well known in electric power generation and chemical process industries.

Lots of operators use Sodium Sulfite or some related form. It is the common industrial standard. It raises havoc in locomotives. In wet layup, it actually promotes pitting at the water line if exposed to oxygen. It causes mixed-metal galvanic corrosion with bronze fittings attached to steel. In operation, sulfite is a notorious foam generator. Many gallons of anti-foam have been used to counter-act the unwanted side effect of using sulfites.

Times and technology has changed. We now have an chemical oxygen scavenger that does not cause foaming, pitting or galvanic corrosion. It is catalyzed so that it does not activate until it reached 160 F. It will not decompose in a cold tender tank. It will protect feedwater heaters and hot delivery piping. The presence of the chemical can be tested to verify ongoing protection. The new Oxygen Scavenger, RustStop 85, can be used with all boiler water treatments. It is an Amine, meaning it slowly beneficially releases ammonia related vapors ( in the minute PPM range ). This raises the pH of the steam and condensate, reducing the tendency for Carbonic Acid gouging of steam and condensate piping. This has been used and tested by an independent engineering agency in a large steam locomotive in the USA. I don't have permission to release the name. Their corporate office will eventually release the report.


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 Post subject: Re: Best Practice Between Steaming Days
PostPosted: Fri Oct 19, 2018 1:07 pm 

Joined: Wed Aug 25, 2004 11:16 am
Posts: 767
How does sulfide promote pitting if the delta G of reaction is 100 percent for sulfide oxygen reaction? Further if the boiler is suppose to be a closed system where did the oxygen originate? Finally were sulfide levels maintained or were they allowed to drop removing the protection?

Robby Peartree


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 Post subject: Re: Best Practice Between Steaming Days
PostPosted: Fri Oct 19, 2018 4:50 pm 

Joined: Mon Jan 09, 2017 10:35 am
Posts: 31
Agreed, Robby, the delta G = 100 % means that the reaction of Sulfite to Sulfate proceeds until either the sulfate or the oxygen is completely used up.

Both Sulfite ( SO3 ) and Sulfate ( SO4 ), which is the waste product of chemically scavenging dissolved oxygen from water, are highly conductive. This causes a strong
increase in the surface tension of the water. All boilers foam to a degree. The big problems occur when the steam space becomes full of steam bubbles and their skin of boiler water. If the boiler is not clean, loaded with abrasive rust and scale, that causes gouging of valves and cylinders. It also forms corrosive and thermal insulating deposits leading to premature superheater failure.

A locomotive boiler is not a closed system. Oxygen is constantly coming in with feedwater in operation. In cold wet layup, we hope it is a closed system, if it is closed and a nitrogen blanket with regular purging is applied and maintained. If outside air is allowed in, the sulfite to sulfate reaction will remove what it can.

Sadly, too many times a method or chemical treatment is tried, but the complete picture may not be thoroughly understood. Sometimes the control limits or assurance steps of routine testing may be missed. In this historical steam preservation community, there is always a shortage of manpower, time, training, timely and complete follow-through. That is why we strive to simplify and use common terminology; help folks understand want can be a complex and difficult topic.

Below is a scientific report, which I have edited to eliminate the non-pertinent. Read the entire publication if you like, the sources are listed first

https://www.researchgate.net/publication/284702876_Corrosion_behavior_of_carbon_steel_in_oxygenated_sodium_sulphate_solution_under_different_operating_conditions

Originally published in; Advanced Chemical Engineering Research Vol. 2 Iss. 3
Corrosion Behavior of Carbon Steel in Oxygenated Sodium Sulphate Solution under Different Operating Conditions Basim O. Hasan* and Sara A. Sadek Chemical Engineering Department, Al-Nahrain University, Iraq *Corresponding author:basimoh99@yahoo.com

“…The anions most commonly found in water are chloride, sulphate and bicarbonate. There are many investigations on corrosion of carbon steel in neutral aerated salt solutions, especially in sodium chloride (NaCl) solution. Little investigation has been found for corrosion of carbon steel in Na2SO4 salt solution. The sulphate ion has a greater effect on the corrosivity of the water than the chloride ion, and the bicarbonate ion shows inhibitive tendencies…Sodium sulphate also cusses corrosion in boiler in which sodium sulfite (Na2SO3) is utilized as oxygen scavenger when Na2SO3 reacted with oxygen at low temperature and pressure, sodium sulphate is created that causes severe attack to the tubes of ( a ) boiler [Huijbregts, 2007]…
The following reactions occur as the result of the corrosion of carbon steel in sodium sulphate (Na2SO4) aqueous solutions [Peralta et al., 2002]:

Fe(s) ↔ Fe +2 + 2e-

(1) 3SO3 -2 + Fe3O4 ↔ 3Fe(s) + 3SO4 + 6e-

(2) It is well known that the rate controlling step in most natural water corrosion process is the cathodic half reaction. The most important cathodic process in aerated waters is oxygen reduction. The rate of this half reaction is generally limited by the speed at which oxygen can reach the surface of the metal. This oxygen is transported from the bulk water to the surface across the boundary layer by diffusion. The oxygen concentration will vary from a minimum at the surface to bulk concentration at the outside edge of the boundary layer, which results in the concentration
It is widely recognized that the corrosion of carbon steel in aerated neutral solutions may be explained by the anodic reaction as in Eq. (1) and cathodic reaction in presence of oxygen:

½ O2 + H2O + 2e− → 2OH−

(3) In general, as the corrosion proceeds, the process becomes more complex due to building up of corrosion products which restrain the oxygen transport to the surface… “

In other words, Having a basic chemistry, pH between 10 and 11 a protective magnetite hydroxide layer, chemical oxygen scavenger and a nitrogen blanket,
is the " Belt and Suspenders " method of not getting caught with pants down ;-).


Last edited by Boiler Water on Sat Oct 20, 2018 9:07 am, edited 1 time in total.

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 Post subject: Re: Best Practice Between Steaming Days
PostPosted: Fri Oct 19, 2018 7:15 pm 

Joined: Thu Feb 27, 2014 10:08 am
Posts: 705
Boiler Water - for the nitrogen purge you appear to use a cylinder of gaseous nitrogen. Have you tried a liquid source? It seems for a long layup, a liquid tank may last longer, especially at the lower pressure you are calling for as the boil off rate would be very low. A liquid source is also very clean and dry and in most cases poses a lower risk of catastrophically oversupplying a large amount of inert gas in a short amount of time.


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 Post subject: Re: Best Practice Between Steaming Days
PostPosted: Sat Oct 20, 2018 9:41 am 

Joined: Mon Jan 09, 2017 10:35 am
Posts: 31
Scranton Yard - All of my clients in the historic steam preservation community use 200 Cubic Foot compressed gas cylinders. That is convenient for the volume of nitrogen needed and the maneuverability and handling logistics.

Many of my industrial and utilities contacts do use large cryogenic tanks. These range from about 1,700 to 5,000 cubic feet of nitrogen expanded to gas at atmospheric pressure. These tanks are not portable when full, but are forklift portable empty.

Previous posts asked the question of draining superheaters. The best method I know is to apply the nitrogen while the boiler is still hot, about 5 psi steam pressure. Apply 25 psi of nitrogen temporarily, in reverse flow through the superheater. While doing this, vent steam off the saturated side. The heat remaining in the boiler will dry the superheater tubes while the nitrogen purges the vapor out. After this, place the low pressure regulator ( 11 inches of water ) on the nitrogen supply and maintain this until the boiler cools below 120 F. Puff purge the boiler weekly for 15 minutes with nitrogen.

This is a standard procedure for large electric power generating plant boilers, where the superheater elements are vertical pendants, often 100 feet long, with no bottom drain. I worked for many years in that industry, sharing it with the historic steam RR community.


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 Post subject: Re: Best Practice Between Steaming Days
PostPosted: Sat Oct 20, 2018 12:01 pm 

Joined: Thu May 24, 2012 1:37 pm
Posts: 2213
Quote:
"Apply 25 psi of nitrogen temporarily, in reverse flow through the superheater."


How would you set up to do this on a typical locomotive, and what special fittings and procedures would you need? Seems to me that at the least you'd need a fitting in the lines going down to the cylinders, and roll the engine to give lap seal on both sides before pressurizing. Might it be possible to arrange something that would survive smokebox conditions and provide a gastight valve to the outside of the smokebox wrapper...

Even then, I still think it's something of a crapshoot that you purge all the elements completely, even with considerable residual heat. Would providing hot air 'blast' through the flues from the firebox end sequentially from 'bottom to top' help ensure all the moisture is purged from every element? How easy would it be to access the header to test for the absence of moisture there?

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 Post subject: Re: Best Practice Between Steaming Days
PostPosted: Sun Oct 21, 2018 11:37 am 

Joined: Mon Jan 09, 2017 10:35 am
Posts: 31
As 'airforcerail' Adam McDowell posted above, the use of a humidity indicator ( and / or humidity indicating dessicant ) is worthy of consideration. For purging, inerting and recycling, the piping connections do not need to be large diameter.

If a locomotive has a front end throttle, the isolation of the superheater seems intuitive.
If a locomotive with a superheater has a dome throttle ( rare ), the cylinder feed shutoff ( valve lap ) and purge piping would be a consideration.

Use a small rotary air pump to force recirculation of dry nitrogen through the parallel superheater elements, from outlet to inlet, or vice-versa. Include a dessicant packet with some visibility of the color. A 2-1/4" x 9-7/8" standard clear plastic water filter housing with a riser tube added would work below 100 F. If the dessicant turns pink, indicating the presence of moisture, change it out with fresh dessicant.

A little imagination combined with shared wisdom will make the best out of a challenging situation. Is it a ' crap shoot ' ? All further suggestions are welcome.


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 Post subject: Re: Best Practice Between Steaming Days
PostPosted: Sun Oct 21, 2018 6:03 pm 

Joined: Sun Aug 22, 2004 7:19 am
Posts: 6399
Location: southeastern USA
Boiler Water wrote:
If a locomotive has a front end throttle, the isolation of the superheater seems intuitive.
If a locomotive with a superheater has a dome throttle ( rare ), the cylinder feed shutoff ( valve lap ) and purge piping would be a consideration.


Rare? No..... at least not on smaller locomotives or those converted to superheat during their operating careers. I think where Bob K and I have had different experiences with the blowing out with a boiler full of compressed air - those diesel electric air compressors on wheels seem convenient for this purpose - is that his locomotives are about 4 times larger than what I have worked on.

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 Post subject: Re: Best Practice Between Steaming Days
PostPosted: Sun Oct 21, 2018 7:58 pm 

Joined: Mon Jan 09, 2017 10:35 am
Posts: 31
Dave,
Thanks for enlightening me on the population of dome throttles with superheaters. There is always something to learn ...

A comment on using compressed air in a boiler, I would avoid air loading on top of water. The air with 20.9 % oxygen will diffuse in the water. This would be inviting rusting.


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 Post subject: Re: Best Practice Between Steaming Days
PostPosted: Sun Oct 21, 2018 10:40 pm 

Joined: Sun Aug 22, 2004 7:19 am
Posts: 6399
Location: southeastern USA
Agree Jim - this is for after season layup preparation, to get enough out so the elements won't freeze and split over winter.

I think we need to think most about what low tech easily reproduceable options there are for many of us that don't have facilities to provide nitrogen for months at a stretch, or even indoor storage space.

Your time spent explaining how your techniques work was certainly of great interest when we met in Savannah. Cleared up a lot of murky things for me.

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 Post subject: Re: Best Practice Between Steaming Days
PostPosted: Sun Oct 21, 2018 11:49 pm 

Joined: Wed Aug 25, 2004 11:16 am
Posts: 767
I do not see how the report linked above is with agitation speed and atsmosphereic oxygen interface is relevant to a stagnant boiler with no fluid flow and should be sealed from letting O2 in.
Railroads in the days of the boiler wash used to do the work in a shift. The only way they could accomplish this is by draining the boiler while it was still under pressure. We blew a blow down valve on a steam locomotive with 200 psi on it and I remember the speed that the boiler drained of water even before the pressure completely dropped. A lot of RR boiler wash would have beensimular in treatment to the boiler as I understand procedures. The SP in El Paso and many other places used one boiler to keep multiple boilers warm with steam. With the definition of a service day requiring both pressure and fire for a locomotive with a firebox, would a heat boilers in order? I know at at least one RR it would reduce service day useage.
I have not found a historical layup procedure yet does anyone have one that they are willing to share.

Robby Peartree


Last edited by Robby Peartree on Mon Oct 22, 2018 7:02 pm, edited 1 time in total.

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 Post subject: Re: Best Practice Between Steaming Days
PostPosted: Mon Oct 22, 2018 7:15 am 

Joined: Sun Aug 22, 2004 7:19 am
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Location: southeastern USA
Because you can't seal a boiler to the extent that oxygen casn't find its way in. Displacing it with another more inert gas at low pressure will take up the space, but as that inert gas leaks out you will need to replace it also.

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 Post subject: Re: Best Practice Between Steaming Days
PostPosted: Mon Oct 22, 2018 8:08 am 

Joined: Thu Sep 22, 2011 4:29 pm
Posts: 1899
Location: Youngstown, OH
This is a great thread! The kind of stuff that we need more of here on RYPN.

I have followed Jim's advice and have started to set up a nitrogen blanket rig in J&L 58's enginehouse. I converted one of my oxygen cylinders over to Nitrogen and mounted it in the enginehouse so that when 58 is pulled in after a day's running I can make the connection to the dome and turn it on. Hopefully I get to try it out next season when 58 starts running.

I'm not sure how often we will run 58 in the summer. Might be every weekend if it looks like there will be customers who want to come see it run. Water conservation will be a big component of our operation since our site does not have a water source. Tanks must be filled by bringing in water from off site, meaning draining and refilling needs to be kept to a minimum.

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 Post subject: Re: Best Practice Between Steaming Days
PostPosted: Mon Oct 22, 2018 8:53 am 

Joined: Wed Aug 25, 2004 11:16 am
Posts: 767
Dave wrote:
Because you can't seal a boiler to the extent that oxygen casn't find its way in. Displacing it with another more inert gas at low pressure will take up the space, but as that inert gas leaks out you will need to replace it also.

What do you do a hydro with a a fire truck so you have enough capacity to overcome the leaks? There some chemistry here that I think is miss umderstood.

Robby Peartree


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