Tube Leaks in Brand New Boilers?
Tube Leaks in Brand New Boilers?
(OP)
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?





RE: Tube Leaks in Brand New Boilers?
RE: Tube Leaks in Brand New Boilers?
RE: Tube Leaks in Brand New Boilers?
RE: Tube Leaks in Brand New Boilers?
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!"
RE: Tube Leaks in Brand New Boilers?
RE: Tube Leaks in Brand New Boilers?
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.
RE: Tube Leaks in Brand New Boilers?
RE: Tube Leaks in Brand New Boilers?
RE: Tube Leaks in Brand New Boilers?
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?
RE: Tube Leaks in Brand New Boilers?
RE: Tube Leaks in Brand New Boilers?
After you re-roll the tube, did you hydro test the boiler before putting it back in service?
RE: Tube Leaks in Brand New Boilers?
RE: Tube Leaks in Brand New Boilers?
RE: Tube Leaks in Brand New Boilers?
What you have not told us is where about were these tubes leaking on the tube sheet?
RE: Tube Leaks in Brand New Boilers?
"Nobody expects the Spanish Inquisition!"
RE: Tube Leaks in Brand New Boilers?
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!
RE: Tube Leaks in Brand New Boilers?
"Nobody expects the Spanish Inquisition!"