Automatic surface skimmer control systems allow more control over your boiler's conductivity and reduce levels of solids and particulates in your boiler water. They are set on a timer to take a sample of water 3" to 6" within the boiler level. The sample is compared to the setpoint on a specified time schedule, and if its conductivity is too high a blowdown valve opens and stays open until the sample drops below the conductivity setpoint.
Why It Makes Sense
Different boiler systems allow for slightly different levels of control, but having a skimmer installed makes sense for most in terms of water treatment and energy savings. Surface skimmers reduce particles and suspended solids in boiler water, and having them operate only when necessary saves on energy and fuel consumption. Automatic surface skimmer control systems are very efficient because they optimize surface blowdown rates while reducing the solid content of your boiler water.
Automatic surface skimmer control systems also provide a way to keep conductivity at its proper rate. By having more consistent control over chemical treatments, you can save money and manpower. In fact, with internal treatment chemicals at proper levels, you use fewer chemicals to adjust the levels and spend less time testing and calibrating your measurements.
Proof of Savings
Say the installation of an automatic blowdown control system reduces your blowdown rate from 8% to 6%. If your boiler efficiency is at 80% with your fuel valued at $8.00 per million Btus, your total water, sewage and treatment costs are around $0.004 per gallon. Your initial boiler feedwater is 108,696 lb/hr and the final is at 06.383 lb/hr, so your makeup water savings would be 2,312 lb/hr.
Enthalpy of boiler water would be 28 Btu/lb, which gives you an energy savings of 310.5 Btu/lb. That adds up to an annual fuel savings of $62,886 and annual water and chemical savings of $9,714. Your total cost savings per year would be $72,600, which is quite a savings for most boiler users.