January 23, 2017
replacing it with fresh makeup water with lower levels of TDS, thereby lowering the overall TDS in the boiler.
Typical Installation (See timed‐sampling drawing)
A. Required components
Conductivity probe and mounting cross should be installed as close to the skimmer port as possible in a 1” fully ported line with no bends or restrictions. An isolation valve should be installed upstream of the conductivity probe for ease of probe removal and maintenance.
2) A flush valve (1/4 turn ball valve) should be installed on the bottom leg of the 1” mounting cross for sediment removal and probe cleaning.
3) The throttling valve should be installed between 6” and 3’ downstream of the conductivity probe to prevent steam flashing across the probe.
4) The blowdown valve should be located far enough downstream of the throttling valve to distance it from high temperature areas. Many blowdown valves feature thermal cutoff switches that can be triggered by high ambient temperatures.
Automated Blowdown Cost Justification
hat is the most common “objection” to the purchase of an automatic boiler blowdown system?
Right, it costs too much! Here’s a suggestion to help overcome that objection. Analyze the operation and come up with the payback figure.
Take the following example:
A process boiler producing 100,000 pounds per hour of steam: The operator has been told to maintain chlorides at 18‐22 ppm. His records show that he averages 20 ppm, which is pretty good for manual blowdown.
However, automatic blowdown could bring the average up to 21 ppm without exceeding 22. This would reduce the blowdown by 5% (21‐20) / 20 = .05 or 5%
Typically, 20 ppm results from 10 cycles of concentration. The blowdown required to maintain 10 cycles is 10,000 lbs/hr (100,000 / 10 = 10,000)
If the 10,000 lbs/hr is reduced by 5%, that’s a savings of 500 lbs/hr. 500 lbs/hr at 400 BTU/lb is 200,000 BTU/hr. A gallon of oil is about 100,000 BTU, so the oil consumption will reduce by 2 gal/hr. At a dollar a gallon, that’s a $2 savings every hour!
If an automatic blowdown system costs $1300, it will take 650 hours (or 27 days) to pay for the system!!! ($1300 / $2 per hr = 650 hours); (650 hours / 24 = 27 days)
This was all based on zero condensate return. If there is 50% return, the payback period doubles in 54 days. That’s still a very short payback period. Of course, the savings continue after the payback period.
Comments will be approved before showing up.
March 02, 2021
March 01, 2021
February 08, 2021