Tube Leaks in Brand New Boilers?

[MechItHappen]

Just wondering if it is common for scotch marine fire tube boilers to have tube leaks within the first one-two years of operation. Is there a typical timeframe where you would expect the first tube leaks to occur? Would it be more of an operational fault (short cycling or thermal shocks?) or more likely a fault in the manufacturing of the boiler?

 

[pkaiser]

Have the same question. Who is the manufacturer? I'm having the same issue on a brand new boiler with only 833 hrs run time. 12 leaks originally 4th pass front and back and that went downhill quickly. I know that it was not operational or chemical addition issues.

 

[chicopee]

Is this a two or four pass boiler? Who is the manufacturer? where was it manufactured and tested? does it have a National board number are the tubes leaking at the front or rear tubesheet? did you open up the boiler and looked at the conditions of the tube surfaces? Unless you tell us more about the boiler as with the above questions and more from other responders, we can not give you some reasonable explanation .

 

[bpv66]

Almost all of the tube leaks that I have seen on newer boilers are due to poor water chemistry.

 

[davefitz]

Most boilers follow a similar statistical leak profile- the first year of leaks may be due to manufacturing defects, the intermediate 2-6 yr may be due to incorrect operation, then corrosion, fatigue and creep start their inevitable toll.

Leaks in the 1-2 year period sound like incorrect operation or a grossly mal-designed boiler. You might be starting up or operating the boiler incorrectly. If the boiler is from a no-name fly-by night company, then it might have been grossly mal-designed.

"Nobody expects the Spanish Inquisition!"

 

[pkaiser]

York-Shipley 4 pass dryback. Only 833 hrs of operation on it. Manufactured and tested in York, PA at their facility. We had a metallic banging sound coming from the burner front. Sounded like the division plate between the 3rd and 4th pass. Had the Prime open it up and found phosphate all over the 4th pass tubes. Opened the rear and found the same thing in the 4th pass but opposite side. My staff and 2 independent water treatment companies have been doing the chemistry on theses boilers since startup in March 2015 and all have the same readings and results to verify correct chemistry. Operational logs are complete and in good order. We have left all the boilers warm and run them up several times a day to keep them warm during the acceptance phase of the project. The majority of my staff are ex navy with years of boiler operations and repair experience. None of us have ever seen leaking tubes this bad in new boilers especially in the 4th pass. They tried to hand re-roll the tubes and could not get them all to seal, the Prime then started mechanically re-rolling tubes and this created more leaks that they were chasing in the 3rd and 4th passes. They ended up re-rolling the entire 4th pass front and back and leaks shifted to 3rd pass. there are 264 tubes in this boiler and the 4th pass has 80 tubes so they have re-rolled almost 200 tube ends. I definitely think this was a manufacturing defect and we are in discussions but I'm out of my swim lane on this one. I have over 35 years of experience in operations, repair, and administration of boilers and utility systems and can't remember a time I've ever heard of this many leaks upfront in the first 6 months. 1 or 2 tube end leaks weeping yes but chemical running out and covering the tube sheet no. We are having the Prime open the other 2 once we get this one back in service due to banging on those also and to look for tube issues on those. Thanks for everyone's input.

 

[chicopee]

You would have been better off to seal weld the tube ends.
On the water side, was there any scale on the tubes? Also is the firing rate within the specification? It is possible that scale on the tubes could have cause the leaks during the max. firing rate. It is also possible that the firing rate is excessive for this FT boiler. From my experience, I have seen scale (since feedwater came from a nearby river) was on the on the waterside of the tubes cause the tube ends to leak when the boiler was retrofitted with a NG burner rated at twice the acceptable firing rate.

 

[pkaiser]

There is no scale evidence on the tubes and we use soft water currently for makeup at 0 hardness. DA is producing 0 ppm of dissolve oxygen. We will be shifting to RO water once I have the sensors needed to allow chemical addition, in place. Burners are 10:1 turndown and firing rates have been averaging 20-60% range during the acceptance period. System is equipped with FGR also.

 

[chicopee]

Did pkaiser highjack MechITHappen's post?

 

[gerhardl]

Maybe pkaiser and MechITHappens should have an internal discussion and report back to the thread?

Anyway, for both cases, with no experience in boiler construction and operation (but lots in valves, piping and steam engineering), I wonder why this discussion concentrates on chemical and operational features, and not manufacturing failure.

In my opinion, any mechanical device, even if tested OK, should not misbehave in the degree described here. Any qualified repair or improvement should not shuffle the problem around, instead of giving improvement. The discussion seems to mainly eliminate false operation and wrong feeding water quality.

Anyway, when something is wrong, it does not necessary indicate only one wrong factor.

Questions:
Is this an unknown problem for the factory or systematic fault for several boilers?
If happening for several: for same model, different models, bound to certain production dates, constructions, workers, welding, materials etc. etc. Systematic fault?
If this is a 'one off' construction, what is different, some factors mentioned above? Flow for fluid and heating medium?
The heating/cooling of the tubes (and sealing material/surfaces) with shrinking and expanding seems (on suspicion based on discussion above) to contribute to the leakage (note: no detailed knowledge on construction by me). Checking details on sealing surfaces and fastening details and expansion/crimping forces and distribution related to material strength?

 

[pkaiser]

Sorry everyone. I guess I did.

 

[cmsvessel]

Just to confirm that when you say tube leaking, you mean between the tube and tube sheet.
After you re-roll the tube, did you hydro test the boiler before putting it back in service?

 

[pkaiser]

You are correct. Leaks at the tube sheet. We conducted a hydro that was witnessed by a licensed inspector and accepted as suitable for service.

 

[MechItHappen]

Another point that was brought to my attention was to monitor the stack temperature. There is some literature that indicates condensation could form in the stack below 250F and accumulate on the tubes. We ran large scotch marine boilers during the summer at extremely low firing rates since our summer boiler was out of service. In retrospect, probably should have locked low fire at 10 or 15% and deal with the extra cycles per hour.

 

[chicopee]

If it were condensation then you have no tube leaks. I have to concur with you that during humid summers condensation could be a problem at low firing rates as I have seen a WT boiler developing condensation within its economizer and this condensation took the appearance of dark molasses.
What you have not told us is where about were these tubes leaking on the tube sheet?

 

[davefitz]

I have heard that one issue with packaged boilers is damage due to shipping shocks. It probably would be prudent to specify that accelerometers be added to the boiler prior to shipping, so that a record of shipping loads ( eg , dropping the boiler while unloading from a ship)can be maintained, and damage apportioned to the shipping company.

"Nobody expects the Spanish Inquisition!"

 

[pmover]

this is written from firsthand experience with boilers of this type.
i have seen several instances of this occuring. since most of these locations were exposed to cooler climates (New Mexico), condensation was also a problem resulting from cooling of exhaust gases below dewpoint temperature.
the only explanation i can offer is that the thermal cycles (boiler cycling on/off) allow the tube expansion to be greater than the boiler shell/tubesheet. afterall, the hot gases are flowing through the tubes with cooler water outside of tubes. this possibly causes flexing or bowing of the tubesheet at the various passes. as the thermal cycles are high (?) and the constant on/off operation allows the tube(s) to become unseated from the tubesheet and thus leak. the remedy is simply to get the tube roller out and re-seal the tubes a little more snugly than initially accomplished.
condensation would most often be seen at the outlet of the last pass. possibly,
with regards to the condensation, the boiler may be oversized for the application. your post about fixing the firing rate at minimum position may help with this in keeping the boiler exhaust temp operating above dewpoint temperature and keep the boiler operating at longer periods (reduce on/off cycles).
as a last thought, if the boiler is mounted on a skid, check the bolts at the rear of the skid where the boiler shell/framework/footing attaches. if these bolts are tight, inquire with the mfg about loosening these to allow the boiler to flex/grow when in operation. i recall a location where the operator observed these bolts being "loose", so he tightened them. not a good idea as the boiler needs to grow thermally.
good luck!

 

[davefitz]

pmover has a point. If the holes are slotted , that usually means the bolts should be loose, to allow for thermal growth.

"Nobody expects the Spanish Inquisition!"