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Clean Corn Stove Tubes Improve Corn Stove Efficiency

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  • amaizingcorn
    Model 7100 has Firetubes . Fire, Flames, or hot gasses enter the inside of the pipes or heat exchanger tubes. Room air flows across the outside of the pipes.
    Message 1 of 1 , Nov 15, 2006
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      Model 7100 has "Firetubes". Fire, Flames, or hot gasses enter the
      inside of the pipes or heat exchanger tubes. Room air flows across
      the outside of the pipes.

      Model 2100 & 4100 has "Airtubes" similiar to "Watertubes". Room air
      flows inside the tubes. Fire, flames or hot gasses flow outside the
      tubes.

      How important are clean tubes? Note the statement below that soot has
      many times the insulating characteristics of insulation material. Be
      grateful for airtubes rather than watertubes. How would one clean
      mineral deposits off the tubes of a water boiler?

      Are You Keeping Customers' Boiler Tubes Clean?
      00/05/0000 by Steve Spielmann
      There are two types of tubular boilers: firetube and watertube. In
      the watertube boiler, water is carried in the tubes and heated until
      it becomes high pressure steam. In most areas, watertube boiler
      plants must have licensed stationary engineers on hand at all times,
      and maintenance is usually performed by in-house personnel.
      In the firetube boiler, water surrounds the tubes and hot gasses
      travel through them. This results in soot and scale deposits
      accumulating within the tubes. No matter what fuel is used, the tubes
      need to be cleaned regularly. If they aren't, boiler efficiency is
      sacrificed and fuel wasted. Soot actually has five times the
      insulating capacity of asbestos.


      For example, a 18-in. coating of soot can accumulate in a firetube
      boiler in just two weeks, resulting in a heat loss of 47% and an
      increase in fuel consumption of 812%. As the layer of soot builds up,
      the stack temperature rises. For every 40F rise in stack temperature,
      boiler efficiency is reduced by 1%. That's a pretty good argument for
      regular tube cleaning.
      Some Firetube Cleaning History
      Over the years, several methods have been developed for cleaning
      boiler firetubes. Twenty-plus years ago, one popular method was the
      use of soot blowers: steel tubes fitted with blowing nozzles that
      were mounted on the tube sheet of the boiler. They were mounted in a
      way that allowed nozzles to be maneuvered to blow steam or air
      through each tube.
      Soot was simply blown out through the smoke stack and into the
      atmosphere — a practice that is frowned upon today. Today, soot
      blowers are used mainly in large power utility boilers where the
      smoke stacks are equipped with scrubbers and other environmental
      devices.
      Another tube cleaning method practiced by some boiler technicians was
      washing out the tubes using a fire hose. One can imagine the mess
      this left behind. Yes, the tubes were cleaned, but the boiler room
      was left with a layer of black mud on the floor. It took longer to
      clean the floor than the tubes.
      In most cases, tube cleaning was strictly a manual operation
      requiring a great deal of time, labor, mess, and inconvenience.
      Brushes fastened to long, heavy metal rods were manually pushed and
      pulled through the soot laden boiler tubes, resulting in clouds of
      soot filling the air and settling on every surface in the room.
      The backbreaking effort went on for hours, followed by the immense
      task of individually vacuuming each tube and cleaning up the boiler
      room.
      Now for Watertubes
      Most watertube boilers have tubes in a more or less vertical
      position. Though some have straight tubes, which can be cleaned as
      described above, most watertube boiler tubes have bends in them,
      making them more difficult to clean.
      In addition, where firetube boilers commonly have only soot and ash
      to be removed, watertubes commonly have scale deposits that adhere
      stubbornly to the tubes.
      The amount and nature of the scale are determined by the water
      quality and the effectiveness of water treatment. Scale is formed
      when water is heated and suspended solids in the water precipitate
      out onto the heating surfaces. A well-managed water treatment program
      is essential to minimizing scale deposits.
      Early watertube cleaning devices used cylindrical air motors fitted
      with complicated cutter heads fastened to the end of a heavy
      compressed air hose. The entire motor/cutter assembly was then fed
      manually through the tubes and cleaning was performed dry, followed
      by a flushing with a water hose. Each air motor was good for only a
      narrow range of tube sizes, so if the user had many tube sizes to
      clean, he had to have multiple air motors, which drove up the cost.
      Good News: There are Better Ways
      Over the years, great strides have been made in tube-cleaning
      technology. Equipment is now available that enables one operator to
      perform two tasks at once in a fraction of the time.
      For firetubes with soot deposits, there are machines that
      mechanically drive brushes or scrapers through the tubes, requiring
      almost no human effort. These machines are, in turn, connected to
      powerful vacuums that draw the loosened soot from the tubes
      simultaneously, leaving the tubes, boiler room, and operator
      completely clean.
      Some firetube boilers develop scale deposits. This is particularly
      true with waste heat boilers and boilers fired on lesser quality
      fuels. Some of the worst waste heat boilers are found at hospitals
      where medical waste is burned in incinerators and a boiler is used to
      capture the subsequent heat generated. In many cases, a straight
      brushing action isn't sufficient, and rotary equipment must be used.
      Manually fed rotary systems are available that incorporate
      simultaneous vacuuming as well. Many of these systems were based on
      designs originally intended for condenser and chiller tube cleaning,
      and they work extremely well on scaled boiler tubes.
      There is also equipment now available with more powerful air motors
      that drive flexible shafts fitted with a wide variety of cleaning
      tools. The flexible shaft is sheathed in a water-tight casing that
      transports water right to the cleaning tool. This allows tubes to be
      cleaned and flushed in a single operation.
      About Chemical Cleaning
      Chemical cleaning has been used on boilers for many years and is
      still periodically needed to clean the waterside of firetube boilers.
      Chemicals effectively remove calcium carbonate and other scales that
      adhere to heating surfaces. However, this method should only be
      performed when deemed necessary by technicians trained and equipped
      to do the work safely. Chemical cleaning presents the following
      challenges:
      • Cost - chemicals are expensive
      • Safety - chemicals present potential danger to personnel and
      equipment
      • Environmental concerns - what if there is a spill?
      • Time - chemical cleaning can add up to a week to an outage.
      Considering these challenges, it's important to know when a boiler
      needs chemical cleaning. It's worse to chemically clean a boiler that
      doesn't need it than to not clean one that does. Improving water
      chemistry and start-up practices can extend the time between
      cleanings.
      Efficiency Testing
      Every boiler maintenance program should include regular efficiency
      testing because such tests reveal trends that indicate it's time to
      clean the boiler. For example, an increase in stack temperature
      frequently signals soot or scale build up. An electronic combustion
      efficiency tester should be considered standard for the maintenance
      program. They are absolutely essential for tuning the burner
      properly. Many models of testers are available today with
      capabilities to measure and/or calculate net stack temperature,
      oxygen, carbon monoxide, carbon dioxide, nitrous oxide, excess air,
      and other values.
      Regular boiler maintenance that includes thorough cleaning of the
      boiler tubes will result in lower operating costs and fuel
      consumption, greater efficiency and longer heating system life.
      Steve Spielmann is the customer service and technical manager at
      Goodway Technologies Corp., Stamford, CT. He has been in the HVAC
      maintenance business for more than 27 years. He can be reached via e-
      mail at: sspielmann@...
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