Carry-over After a Change of Water Treatment Supplier

The most likely cause is carry-over driven by high boiler water TDS. The measured TDS of 4200 ppm exceeds the stated limit of 3500 ppm, and halving the blowdown frequency would allow dissolved solids to concentrate. High TDS raises the surface tension and foaminess of the boiler water, so steam leaving the drum entrains droplets, which shows up as wet steam, droplets in the header sight glass, and traps passing more than normal. The feedwater hardness of 0.5 ppm does not contradict this; it is within the contractor's target and indicates the softener is working, but softness does not control TDS. The key distinction is that hardness control prevents scale, while blowdown controls dissolved solids and suspended matter. The change in oxygen scavenger dose is less likely to be the cause, though an excess of some volatile treatments can contribute to foaming. The evidence points to inadequate blowdown as the primary cause, with the possibility of organic contamination from the laundry's own return condensate or process water that should also be checked.

In the next hour I would increase blowdown, using the continuous blowdown to bring TDS down gradually and the bottom blowdown in short, controlled bursts to remove sludge from the low points. I would not dump a large volume at once, because a sudden drop in water level and pressure can cause thermal stress and unstable firing. I would test boiler water TDS, alkalinity, and chloride, and test condensate for contamination, because condensate return can carry organics or salts from the laundry process. I would check the steam separators and the drum internals if accessible, and verify the continuous blowdown valve is actually open and not plugged. I would also confirm the blowdown schedule in writing with the new contractor and compare it with the boiler manufacturer's recommended limits and the previous contractor's records. To confirm the diagnosis, I would look for a fall in TDS and a simultaneous improvement in steam dryness and trap behaviour after blowdown, and I would check whether the problem recurs as TDS climbs again.

I would explain that feedwater hardness and boiler water TDS measure different things. Soft feedwater prevents scale on the heating surfaces, but it does not remove the dissolved solids that enter with the feedwater and concentrate as steam is produced. Those solids must leave via blowdown, and the measured TDS of 4200 ppm shows they are not leaving fast enough. Wet steam is not just a quality problem: carry-over can deposit solids in superheaters, steam lines, and traps, cause water hammer, and contaminate the laundry product. My recommendation is to keep the boiler on line only while TDS is brought back within limit under a controlled blowdown regime, with increased testing frequency, and to require the contractor to justify the reduced blowdown in writing against the boiler manufacturer's limits. If TDS cannot be controlled, the boiler should be taken off line rather than run continuously above the limit. The decision should be recorded and escalated to the plant manager, not settled between the operator and the laundry manager.