Total dissolved solids. In practice it is estimated from electrical conductivity, read with a meter on a cooled sample in microsiemens per centimeter and converted to ppm. Each boiler has a maximum TDS set by its pressure, design and steam purity needs, and blowdown is adjusted to stay just under it, since running lower wastes treated hot water and running higher invites foaming and carryover.
TDS is at 4,200 and the limit's 3,500, open the continuous blowdown a quarter turn and recheck in an hour.
Cool the sample before reading conductivity, or the meter reads high and you blow down good water.
Also heard as
- total dissolved solids
Related terms
Blowdown
Draining some boiler water on purpose to remove concentrated dissolved solids and settled sludge.
Cycles of concentration
How many times more concentrated dissolved solids are in the boiler water than in the feedwater.
Foaming
A stable layer of bubbles on the boiler water surface that makes level hard to read and carries water out with the steam.
Carryover
Boiler water and the solids dissolved in it leaving with the steam instead of staying in the boiler.