Although all steam boilers must be blowndown to control TDS, excess blowdown results in wasted thermal energy and boiler water treatment chemicals.
See Blowdown for a discussion about TDS and measurement.
Blowdown Control Measures
TDS recommendation is according to boiler operating pressure. For boilers operating up to 300 psi, the typical limit recommendation is 3,500 ppm. As the boiler pressure increases, the TDS recommendation drops to a smaller number.
If boiler blowdown is according to a time or visual-check basis, monitor boiler water with a TDS measurement system
Use a continuous TDS Meter to monitor boiler water and blowdown only when TDS limits are reached
Often the boiler TDS level can be much higher than thesteam system can tolerate. If this is the case, install a steam trap or sample cooler off the steam header, near the boiler, and measure the TDS content of the condensate. Blowdown only when the TDS carryover to the steam system reaches the pre-determined limit.
Install a blowdown heat recovery system