The On-Line Magazine of Rideable Model Railroading

  NUMBER 190

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© August 12, 2012   

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Your Mom Wants You To Wash Your Boiler
Care & Maintenance of Model Boilers

 


file photo used as an example of a Chloe locomotive

 

Written by By Jeff Badger
Shop Superintendent,
Georgetown Loop Railroad
 


Having worked on all sizes of boilers from the smallest (Mamod/Wilesco) to full size steam locomotives, I can tell you that the continued standard practices established for boiler maintenance in a full size locomotive should also be carried over to our smaller versions also. The care of your boiler is of great importance to its life and the efficiency of its operation.

As a former boiler inspector for a 7.5” gauge live steam railroad in California, most locomotives I inspected rarely had any boiler washes done, with owners relying on regular blow downs and/or the use of water treatment. Small boilers on such locomotives as the Chloe (boiler contents right photo) have very narrow water passages in the legs of the firebox and these tend to mud and scale up even with regular blow downs. This creates issues with circulation and can lead to major problems over time.

Why do a boiler wash?
The biggest reason is for maximum efficiency. If you have a slight buildup of scale, say an overall average of .031”, you are losing 5% of your heat transfer. Loss of heat equals more fuel. If the scale build up continues, you risk burning tube ends, side sheets can bulge and cause stay-bolt failure, tubes can collapse along with other ailments. Or even worse, the potential for a catastrophic failure.


Just a small portion of the scale removed from a Chloe during a re-tube at my shop. The weight was 3 pounds just in this box. (click image)

Old tubes from a Chloe that had a large buildup of scale internally. This caused overheating which led to failure.  (click image)

The life of a locomotive boiler, full sized or model, depends largely upon the attention it receives and the particular locality in which it is used. The amount of use versus the time elapsed between washings varies depending upon the service and water used.

Boiler feed water (water from the tender)
All water contains impurities, which may vary considerably according to the location of their source. These impurities may make the water alkaline or acidic, and depending on mineral content, will form scale or sludge with widely varying characteristics:

  1. Excessive acidity, found in heavily forested areas, will cause problems with corrosion of tubes and steel plates.  An early indication of acidity is the disengagement of existing scale from the plates, stays and tubes;

  2. Excessive alkalinity, found in arid climates, will also cause problems, particularly when even minute leakage paths exist at riveted joints;

  3. Some waters will deposit heavy quantities of hard scale on heating surfaces, particularly fireboxes and tubes, which will become burned, thinned and mechanically weakened due to the insulating properties of the scale. Excessive scale deposits, particularly around the firebox tube sheet, foundation (mud) ring and door sheet will impede water circulation, leading to accelerated scale build up, burning and corrosion.

Feed Water Treatment
If you aren’t actively engaged in utilizing a feed water treatment of some type, you should begin one. The objectives of feed water treatment is...

  1. to keep the internal evaporative surfaces of the boiler clean and free from scale

  2. to prevent corrosion by the control of acidity and reduction of dissolved oxygen

  3. to prevent the solidification of scale-forming impurities in the water and to assist removal of residue at blow down and washout periods

  4. to assist in the prevention of water carry-over (foaming) in the steam due to high levels of dissolved solids in the water;

  5. the selection, application and control of water treatment should be consistent with these recommendations.


The front tube sheet of this boiler has been torched out. Solid scale had embedded completely around the tubes and sheet. Photo Credit Jason B.  (click image)

View of the same boiler with tubes removed and the large amount of scale. Photo Credit Jason B.  (click image)

First off, proper blow downs by the engineer to prevent buildup is very important even if you are using a boiler treatment such as Terlyn LBS or other similar product. Blowing down while running does not necessarily remove all the buildup as most of the solids remain suspended. The removal of sediment or sludge, such as soft scale, mud, etc., can best be accomplished while stationary after the water has had time to settle.

Boiler Wash – Frequency & Procedure
In our smaller boilers, I would suggest that a boiler wash be done annually. In preparing the boiler for a wash, it is recommended to establish a procedure to cool it down prior to washing out. If you are washing out cold, I would recommend filling with water then warming the boiler and water to approx. 90 - 120 degrees. You can raise pressure if you like up to 20 pounds. This will help loosen any impacted debris or mud especially in the corners of the firebox / mud ring. On some locomotives that are heavily scaled, I will add a solution of scale remover to the water before heating. If you have access to a hot water pressure washer, the results are even better.

When the boiler is cooled the natural way, steam should be blown off and the water retained above the top of the crown sheet and allowed to stand until the temperature of the steel in the fire-box is reduced to about 90° F., after which time the water may be drained and the boiler washed. Remove all the plugs from the boiler if accessible. I would also remove the steam dome cover, the boiler check valves, water glass and fittings, try-cocks and the pressure gauge . Open or remove the blow down valves also. You need as much access to the interior of your boiler as possible.

Depending on the size of your plugs and other openings, you need to make a tool for blasting the debris out of the boiler. Your local hardware store should have adapters for a standard garden hose female fitting to a national pipe thread fitting. Utilize the NPT fitting to reduce to a ¼” or 3/16” copper pipe that you will use to wash the boiler. It helps to have two pipes: one straight and one bent at 90 degrees. Also I recommend having a ball valve so you can shut the water supply on and off at the hose adapter end. Once fitted up, determine a length that is suitable for the copper pipe that allows for the most effective reach, attach it to the hose fitting adapter and then pinch the other end so that you will have a nozzle that makes sufficient pressure to remove any debris or scale buildup in the boiler using just the pipe pressure of commercial or home water system. Now you are ready to connect to a water hose.

We begin by first washing the flues at the boiler check valve openings in front of the boiler and working our copper pipe by bending it in and washing to the rear. Be sure to get as much of the front tube sheet as possible also as this is an area that can have buildup especially on the lowest area. Next, enter through the steam dome and wash the top and front of the crown sheet, then between the rows of crown bars, if provided, and staybolts, directing the stream toward the back end of the crown sheet. After washing through the openings near the front end of the crown sheet (if applicable), continue washing through the openings, in order, toward the back end of the crown sheet, in such a manner as to work the mud and scale from the crown sheet toward the side and back legs of the boiler and thus prevent depositing it on the back ends of the flues.

Continue washing, using the openings in the boiler, by manipulating the copper pipe attachment on the hose, working from the front to the rear, to thoroughly wash the top of the boiler as well as all stays and the crown sheet.

Next wash the back end of the flues through the dome opening or other access and afterward the water space between the back head and the door sheet through the openings in the back head such as the removed trycocks and or water glass openings.

If washout plugs are provided in the front flue sheet, remove and wash through them, using the copper pipe nozzle of sufficient length to reach the back flue sheet. If the openings are among the flues, the nozzle should be bent and should be revolved as it is drawn from the back end toward the front.

Again, wash through the openings near the check valves at the front end of the boiler, using straight and angled nozzles. Then wash through the openings in the bottom of the barrel near the rear end, using the straight nozzle directly against the flues and reaching as far as possible in all directions. Both the straight and bent nozzles should now be used through the front opening in the bottom of the barrel, in the same manner as before, to clean the flues and the space between the flues and the barrel.

After washing the barrel completely, use the bent nozzle in the side and corner holes of the water legs, thoroughly clean the side sheets and finally clean off all scale and mud from the mud ring by means of straight nozzles in the corner holes. It should not be assumed that because the water runs clear from the boiler that it is clean and free from scale. Carefully examine all spaces with a light or a boroscope if you have access to one. If necessary, use a small pick, steel scraper, or other suitable tool in removing the accumulation of scale that remains. If your locomotive is light enough, have a friend assist you in turning it upside down for the removal of any large chunks of scale that may not have exited out the small openings but will pass through the steam dome. If there is still accumulation that will not exit, let it dry, and make an attachment to a shop vac that will allow you to remove most or all of what is left.

Now that you are done with the washout, turn your attention to the water glass, try cocks, steam gauge and boiler check valves. Clean these up including their passages to remove any scale buildup, soaking them in a de-scaling solution works best. Let the boiler air dry completely before replacing the fittings and plugs. I prefer to use a good steam rated pipe dope rather than Teflon tape but that is up to you the owner. Once you are finished the boiler is ready for its annual hydro test and should be ready for years of continued use with good maintenance practices.

A footnote of caution: If you suspect your boiler has never been washed, your first successful cleaning and subsequent ones may expose internal problems such as leaky tubes, stay-bolts, and possibly other aforementioned issues. Always hydro test your boiler after it has been cleaned so if there is a problem, it will be exposed.

The title of this article is not my idea. I wanted to call it "Care & Maintenance of Model Boilers". Instead, it's called "Your Mom Wants You To Wash Your Boiler". Sorry about that.

     
   
 
     

Written by By Jeff Badger
Shop Superintendent,
Georgetown Loop Railroad

 

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