Module 12 · Maintenance and Troubleshooting3 min read
Diagnosing Carryover and Water Hammer
Wet steam and banging pipes are symptoms with several possible causes, some in the boiler and some far from it. A few observations, made at the right time and place, separate them.
You'll learn
- Tell boiler carryover from distribution wetness
- Find the cause of carryover
- Classify water hammer by when it happens
- Apply the fix for each cause
Before this: Priming and carryover, Water hammer
BeginnerThe idea in plain words, and where you meet it. No maths.
Where is the water coming from?
Water in the steam either leaves the boiler with it (carryover) or condenses in the pipes on the way (distribution wetness). The quickest test is conductivity: condensate from a separator or drip leg near the boiler with high conductivity contains boiler water — carryover. Clean, low-conductivity condensate means the water condensed in the pipe.
IntermediateThe formula, its units, and a worked example on real plant numbers.
Causes of carryover
| Observation | Likely cause | Check |
|---|---|---|
| Carryover with high boiler TDS | Foaming from dissolved solids | TDS against limit; blowdown control |
| Carryover after a sudden demand surge | Priming: pressure drop swells the water | Load swings; a valve opened quickly; boiler undersized for peaks |
| Carryover with high water level | Level set too high or level control fault | Gauge glass and control set points |
| Carryover with oil or organics in the condensate | Contaminated returns foaming | Condensate source; conductivity or oil monitor |
| Carryover at low pressure | Steam velocity too high in the steam space | Operating well below design pressure |
ExpertThe fine print: where the simple model breaks, and what it costs.
Water hammer: listen to when it happens
| When | Likely cause | Fix |
|---|---|---|
| At start-up | Condensate lying in mains not drained during warm-up | Slow warm-up, open drains, adequate drip legs |
| When a valve opens | Water pushed at steam velocity into a bend or closed end | Drain before opening; open slowly |
| At heat exchanger outlets | Condensate lifted or backed up; stall | Trap and drain arrangement; pump-trap where stalled |
| In condensate return lines | Flash steam meeting colder condensate | Size returns for flash; avoid mixing high-pressure discharge into cold lines |
| On sagging or unsupported lines | Water pockets at low points | Supports, slope and drip legs |
Key takeaways
- High-conductivity condensate near the boiler means carryover; clean condensate means pipe condensation.
- Carryover comes from high TDS, sudden demand, high level, contamination or low pressure.
- Classify water hammer by when it happens; the timing points to the cause.
- Fix causes at the source — water chemistry, drainage, operation — not only with hardware.