Fine droplets and, in severe cases, slugs of water ride out with the steam, carrying dissolved solids and treatment chemicals into steam lines, valves, turbines and process equipment. Causes include water level run too high, high total dissolved solids, foaming, oil contamination, and sudden load swings. Signs include wet steam, deposits on downstream equipment, water hammer and high conductivity in the condensate.
Getting carryover every morning on startup when the dryers all come on at once, the drum level jumps and we ship water.
Running the water level an inch lower and adding blowdown fixes more carryover than any piece of hardware.
Also heard as
- carry-over
- entrainment
Do not mix it up with
- Priming: Carryover is the general loss of water with steam; priming is the violent, slug-sized form of it caused by surging.
Related terms
Priming
Sudden surges that throw slugs of boiler water out with the steam.
Foaming
A stable layer of bubbles on the boiler water surface that makes level hard to read and carries water out with the steam.
TDS
Total dissolved solids: the concentration of dissolved minerals and salts in boiler water, held in range by blowdown.
Drum
A large cylindrical vessel in a watertube boiler where steam separates from water or where sediment collects.