At ARM's meeting in Scranton last fall, Dave Conrad gave a very good talk about the future of operating steam locomotives. One of his concerns was that with the new FRA laws regarding steam engines that operators would be more inclined to leave water standing in the boiler between times and Dave advocated draining and letting the boiler dry out in between times.

My question is this: How long is too long?

Right now, we have an informal policy at NCTM that if an engine is going to sit for more than 3 or 4 weeks without operating, we're going to drain it.

Dave and others out there with thoughts?


http://nctrans.org
Wrinnbo@aol.com

> At ARM's meeting in Scranton last fall, Dave
> Conrad gave a very good talk about the
> future of operating steam locomotives. One
> of his concerns was that with the new FRA
> laws regarding steam engines that operators
> would be more inclined to leave water
> standing in the boiler between times and
> Dave advocated draining and letting the
> boiler dry out in between times.

> My question is this: How long is too long?

> Right now, we have an informal policy at
> NCTM that if an engine is going to sit for
> more than 3 or 4 weeks without operating,
> we're going to drain it.

> Dave and others out there with thoughts?

Jim:

There are several items that have to be considered as to whether the boiler should be drained and dried after use or if a wet lay up should be used.

The first item is, what type of water treatment program is being used. At a minimum, a boiler water treatment program is going to use chemicals that maintain a caustic pH, an oxygen scavenger, and an amine to control corrosion in steam lines.

Second, the primary cause of corrosion in laid up boilers is the presence of oxygen or the presence of water. To eliminate corrosion, one of these two items must be eliminated from within the boiler.

With respect to draining, once the boiler is drained, all water must be removed. To do this, simple draining will not do as a film of water will still be present inside the boiler. To completely dry the boiler interior, two things can be done. One is to put trays of dessicant inside the boiler. The other is to purge the boiler with dry nitrogen until the boiler interior is dry and then put trays of dessicant inside the boiler. Considering the amount of water that can still be inside the boiler after draining, it may take several hundred pounds of dessicant to dry the interior. This is the preferred way of laying up a boiler for an extended period of time, say a year or more.

The alternative is to completely fill the boiler with treated water and adding additional oxygen scavenger. This method is preferred for short periods of storage. While the boiler is stored with a wet layup, chemical analysis should be done on a weekly basis to ensure that there is sufficient residual oxygen scavenger present.

Both methods work well and you can weigh the options to determine which is best for your application.

Another method that might work, if you have a weight limitation and cannot fill the boiler completely with water is the following. Add additional oxygen scavenger. Then, after the boiler has cooled, purge the boiler with nitrogen to remove the oxygen that is present. Then maintain a few pounds of pressure, (say 2 to 3 psi) with nitrogen through a regulator to make sure that oxygen does not get back into the boiler. As with the wet lay up, check the boiler chemistry weekly to make sure that there is sufficient residual oxygen scavenger present.

Just remember, either eliminate the oxygen or eliminate the water and you can delay corrosion.

P. Kurilecz

pkurilecz@yahoo.com

Different Dave same question.

A few years ago I cut out the tubes from the UP 4466 0-6-0 at CSRM which were only a few years old. The tubes had failed due to oxygen pitting. Even the superheater flues were beyond safe ending.

Dennis Daugherty attributed the premature failure to retaining water in the boiler between steamings and at the time advocated draining even if just the days between weekends were to be considered. Apparently the operating and mechanical departments were managed by different folks with different considerations. Not sure what water treatments were in use.

I can vouch for the condition of the tubes, however. That made me a believer in draining for more than 3 days cold, which policy I have used ever since. It may not be scientific but it is practical and doesn't require inert gases and other stuff not always common in enginehouses.

I try to blowdown warm and leave some openings so the retained heat of the boiler will air dry the metal parts.

It won't preserve the tubes forever but it may help.

Dave



irondave@bellsouth.net

Given all the technical advances in coatings since the steam days, isn't there some type of coating that could be applied to the inside of the boiler that would protect the metal from corrosion?

Stuart

gnufe@apex.net

In the boiler industry we call it a wet lay-up or a dry lay-up. The dry lay-up is with out question the way to go for extended periods of time like the off-season. Draining the boiler for the weekdays for a weekend only operation that is a tough one to call.

Some very large plants are moving to “flash draining” of boilers even for periods of a few days, many of these plants also fill the boiler with compressed nitrogen gas which has a dew point of something like –100º F. This low dew point removes any remaining moisture. Compressed nitrogen is excellent for removal of moisture and is used to remove moisture from the tanks of compressed oxygen on the space shuttle before they are filled.

If you drain a boiler while the water is still hot and vent the boiler properly the boiler will dry out inside pretty well but the tubes will be exposed to oxygen in the air and pockets of moisture can still wreak havoc with the boiler. A full boiler drain will also make bottom blowing the boiler unnecessary. This avoids the problem of a stuck blow down out on the road. One the down side draining the boiler with out the proper venting can result in a vacuum inside the boiler. Pressure vessels are not made to hold vacuum and can be damaged very badly if not vented properly.

On the other side of the coin there are argument to leaving the water in the boiler from week to week. If you are using some sort of oxygen scavenging treatment like sodium sulfite of hydrazine properly the water should be deoxygenated to the point that pitting and corrosion should not be a problem. Once you decide to leave the water you need to decide that you must maintain enough blow down to keep dissolved solids from building up on the heating surfaces. These will cause scale and reduce heat transfer and could lead to localized overheating. Most places do a blow down or two every operating day but many never check the level of total dissolved solids, which is why we blow down the boiler in the first place. With out checking the level you never really know if you are blowing down enough.

So folks there are plusses and minuses to both sides and the bottom line is if you donÂ’t understand how all of this stuff works and why you are doing something you may or may not be doing good to your boiler. Education, finding what works, and sticking to one program is probably the key to good boiler operation.

I have been working on and with boilers for 20 years and teach this stuff for as living.


Steam Railroading Message Board
tgears1@home.com

> Given all the technical advances in coatings
> since the steam days, isn't there some type
> of coating that could be applied to the
> inside of the boiler that would protect the
> metal from corrosion?

I think many coatings might be possible for the shell, but would probably interfere with heat transfer on other sheets and tubes. One other major consideration would be thermal expansion. once the coating develops tiny cracks it will actually hold moisture against the metal

Many old traction (steam tractor, not trolley) engineers used to advocate adding steam cylinder oil to the water, and slowly draining while the boiler was warm.I guess it worked okay if the boiler was clean. BUT a tarry mixture of cylinder oil and scale is a real pain to loosen and remove.

For extended lay up periods Santa Fe would add a few gallons of kerosene to the water just before draining. This way everything inside the boiler would have a coating of light oil. All washout plugs were left in except for the two forward firebox plugs. This is from the Santa Fe folio.

At Strasburg,if it will be more than 5 days until the engine is used again, the water will be drained while the water is still hot. As soon as the water is out, all of the washout plugs are removed. Since the boiler is still fairly warm, the water that is left will "flash off" and the boiler will be dry. The next step is to put 2 or 3 heat lamps in the firebox and cap the stack. This method keeps the boiler fairly dry and is very cost effective and most importantly, seems to work.

Muss405@yahoo.com

Another good reason for the heat lamp in the firebox and smokebox is to keep moisture from the soot and converting the sulfur in the soot to acid which then corrodes the sheets.

I have a copy of an old Military Specification (MIL-SPEC) on the preparation of steam locomotives for shipment overseas that mentions a method which could be used.

They said to blow the boiler completely down while still hot, then fill it with hot compressed air. After this, the engine was to be operated briefly so that the hot air dried out any moisture in the superheaters and cylinders. Finally, the remaining air was blown out through the blowdowns which hopefully would thoroughly dry out the boiler.

I'm sure most of you have access to air compressors, but "hot" air may be something else. Anyway, I thought it was worth mentioning.

Good Steaming,
Hugh Odom

> At ARM's meeting in Scranton last fall, Dave
> Conrad gave a very good talk about the
> future of operating steam locomotives. One
> of his concerns was that with the new FRA
> laws regarding steam engines that operators
> would be more inclined to leave water
> standing in the boiler between times and
> Dave advocated draining and letting the
> boiler dry out in between times.

> My question is this: How long is too long?

> Right now, we have an informal policy at
> NCTM that if an engine is going to sit for
> more than 3 or 4 weeks without operating,
> we're going to drain it.

> Dave and others out there with thoughts?


The Ultimate Steam Page
whodom@awod.com

The amount of moisture air will hold is cut in half every 20 degrees the temperature rises. In industry cool air that has been put through a drier will do more to this end.

Tom

Steam Railroading Message Board
tgears1@home.com

???? Tom, this can't be right. Moisture condenses from air as the air is cooled. Water droplets form on the evaporator in an air conditioner. As the air is cooled, it approaches the dew point and the water vapor condenses out. That's the basis of the temperature dehumidification process.

I'll agree that cool, dry air may work fine for the purpose of drying out boilers, but hot, dry air would work even better.

Good Steaming,
Hugh Odom

> The amount of moisture air will hold is cut
> in half every 20 degrees the temperature
> rises. In industry cool air that has been
> put through a drier will do more to this
> end.

> Tom


The Ultimate Steam Page
whodom@awod.com

Sorry. The ability of air to hold moisture doubles every 20 degrees in temperature rise. So often cool air that has been put through an air dryer will be used to absorb moisture. Due to the air being cool it already looses a large portion of it's moisture and when it is put through a dryer it becomes dry to the point dew will not drop out until the air is cooled to -40. At that point the air has the abiliy to absorb moisture and it shoud not drop it back out. I hope I did not foul anyoneup with my error.

Steam Railroading Message Board