Conductivity Excursion and Wet Steam After a Contractor Closes the Continuous Blowdown

Mechanism: carryover from high dissolved solids.

• Without continuous blowdown, dissolved solids concentrate. At high TDS the water surface forms a stable foam blanket instead of cleanly separating steam.
• The gauge glass reads high because the foam blanket sits above the true water line. The level controller is chasing a false level, which is why it hunts. The 'higher level' is not extra water in the drum.
• The ragged, wet plume is steam carrying foam and droplets. The same carryover puts solids into the header, traps and any downstream equipment.
• The water hammer is slug water reaching a low point or trap; traps cycling open on water load is a classic symptom.

Rule these out before you assume TDS is the only cause:

1. A genuine high level - feedwater valve leaking by, bypass cracked open, or level control failure. Blow the gauge glass down and confirm the true level.
2. Oil or organics in the condensate return - a leaking heat exchanger or process contamination foams at normal conductivity too. Sample the return.
3. A softener passing brine during regeneration backwash into the feedwater, which would explain a fast conductivity jump better than solids concentration alone. Check the softener program and the make-up conductivity trend.
4. A real load drop that reduced firing while feedwater was still catching up.

Order matters - you are trying to remove dissolved solids without taking the level away from yourself.

1. Reduce firing rate / load first, so there is thermal and level margin for what follows.
2. Blow the gauge glass down and confirm the true level. Do this before and repeatedly during the cleanup. The glass is now your only trustworthy level instrument if the control is hunting on foam.
3. Open the surface blowdown gradually, not wide open from a dead-closed position. Pipe thermal shock and a sudden level collapse are both real. Bring it to a throttled position and use it as the primary control - target conductivity at or below 3,500 on a properly cooled sample (hot samples flash and read high).
4. Supplement with short, frequent bottom blows - roughly 10-15 seconds each, several times over the cleanup, rather than one long blow. Long blows dump the level and stress the mud drum; short blows move sludge and exchange drum water without collapsing the level.
5. Watch the glass between blows. If the level approaches the low alarm, stop, let the feedwater recover, then resume. Never leave a blowdown unattended.
6. If foam is severe, reducing firing rate plus a vendor-recommended antifoam slug can collapse the blanket so you can see and control the level.
7. Fix the source last, but fix it: repair and tag the continuous blowdown valve, verify the softener, and re-sample the condensate for oil.

• Log conductivity readings, sample times and method, blowdown valve position, duration and frequency of every blow, and the level at each step.
• Trend the data rather than reading it shift by shift; look for the conductivity curve inflecting at a specific time, which points at the contractor's work window.
• Treat contractor work on the boiler water side as a change that must be tracked: tag and lock the continuous blowdown valve normal position, require a documented post-work check that all valves are returned to their operating positions, and add a sign-off before the contractor leaves.
• Notify the water-treatment vendor to verify the softener and the chemical program against the actual make-up and return ratio.
• Check the header and traps for debris and water-logged sections after the carryover, and sample steam condensate for solids to confirm the carryover has stopped.
• Report the event to the chief engineer with the timeline and the corrective actions, since wet steam and water hammer in the header are reportable-quality events at most plants.