So Why Did MY Munchkin Leak?

Perry_5

Sure enough...

The above is a good general answer. Why do you ask?

I try not to get into advanced engineering & science in a forum like this.

Dealing with the operation of boilers and heat exchangers - their degradation - and how to prevent that degradation is what I do. My key job is to find the degradation before it affects plant operation, to identify why the degradation is occurring, to do a failure analysis if it occurs, and to determine if it is reasonable to prevent it from happening again.

I just normally work on a larger scale than home heating boilers and have a large budget in comparison.

Of the HX's I take care of just in the plant I am at I have at least the following list of tubing: Steel, 304 SS, 316 SS, 439 SS, SeaCure, Copper, 90/10 CopperNickle, Admiralty Brass, and Inconel. I probably left a few off the list as I am working from memory. I also have worked with Hastelloy and AL6XN at other plants or positions (and a few other oddballs).

I've crawled through boilers since a kid (home and small business coal boilers). Most of my adult life I've crawled through boilers that are many stories tall. Want to see a boiler fireball. Some of the plants I've worked in have rotating swirling burner fireballs 75 ft across and 200 ft high. Some of those boilers have SS superheater pendents in them (Imagine 2600 PSI, 1050F steam... The boiler tubes and main steam pipes glow dull red if you turn the lights off).

I am not sure I can describe how fouled, scaled, etc I've seen both boiler tubes and HX tubes. I certainly would not even begin to list all of the failure mechanism I've personally seen - not to mention the ones I've studied (I actually go to multi-day seminars on the failure mechanisms of HX materials as part of my job). You would probably surprise me if you can show me something in a home boiler that I have not seen before.

As an example of scale: this past fall we replaced 4 Feedwater Heaters. They each cost an average of $3/4 Million + installation cost of several Million for the 4 (total installed cost for these 4 was in the range of $5-6 Million). I controlled the specifications for all parts of those HXs (tubes, tube supports, shell, head, nozzles, etc). My FW Heaters cost about $75,000 more than the lower cost industry standard material ones. But mine will not have a whole series of problems that most FW heaters have (and that our old ones had) - and they should last at least twice as long -if not 3 times as long as normal. Spending an extra 10% on purchase to eliminate problems is quite acceptable at the corporate level (I did have to justify and go through "Challenge" Boards for all of my upgrades in materials and fabrication processes).

Because of my broad materials failure expertise - I can be asked to help people dealing with pipe and other component failures (pumps, valves, etc).

However, back to the engineering and science I try to avoid on this forum. Of course there are exceptions and really strange situations. Also, of course - every now and then someone shows me something I did not know. I do not claim to be a metallurgist, or an advanced metals physicist or chemist. I am not. I am a "practical" working failure and failure prevention engineer; and I am trying to help on this forum by explaining why these materials and boiler tubes fail.

Have a great day,

Perry

Perry_5

One exception I should mention on the hot spot

Proper boiler design does not expose boiler tubes to direct flame - or even very near flame. Boiler tubes should only deal with hot gases and radiant energy.

Obviously, if someone mis-designs a boiler; or misadjust a burner to where direct flame contact (or very near flame contact) occurs then you can indeed have a hot spot melt a tube.

Just like I can take a cutting torch and cut a tube full of water (and even cut it underwater too).

Perry

Wayne_29

Never mind the science

Does anybody actually install Munchkins anymore?

GREG LAUER

consiter this

Pressure really should not matter. All or the components should be rated for a pressure that high. I would be more worried about flow. If the pump is oversized or is cavitating can be an issue. lets take this one futher though. if install is copper and the joints were not reamed and the pump is oversized the rate at which the copper will pit will increase turbulace in the pipe from to much flow and un reamed joints will tear up a system fast. if it is sized properly it will still happen but at a lower pace. if the holes are withing 3 ft of a joint I would look into this. We had several systems that had pinholes and also had dilectric nipples or unions and we did not know what it was from till a guy from copper develpment came in and gave us a class on copper and everything you can do to screw up a install. I recommend having this guy give you a class if you have never seen it you will learn the way you solder is wrong. Contact the copper development association for details. if the pipe has little fishers in a "j" shape where the pinhole is this would be your problem. I t can also be caused by reducing or expanding the pipesize to much in to short of a distance.

tim smith

I still go with under deposit corrosion. Seen it on quite a few

now. Not always failing yetttt. But definate signs of corrosion.