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The HydroFLOW Limescale Control Device
How Limescale Buildup Affects Boiler Energy Costs
Estimated Household Savings from the Prevention of Limescale Buildup
Estimated Effectiveness of HydroFLOW Limescale Prevention Devices

By Motti Feldleit of the Water Quality Department of the Water Workers Association, June 2005



Introduction
This opinion was written at the request of Pazgas, which is examining the possibility of integrating HydroFLOW limescale prevention devices into gas water heating devices.

The opinion consists of the following sections:
  • A short review of the topic of limescale and its effect on
         heat exchangers
  • Theoretical background for the operation of HydroFLOW devices
  • Tests and impressions following the use of HydroFLOW devices
         in Israel
  • Opinion summary
  • Appendices


  • Limescale and its Effect on Heat Exchangers
    Limescale originates in the components of the water's carbonic rigidity - calcium carbonate (lime), magnesium carbonate, calcium sulfate, calcium phosphate and sediment formations. In Israel, the main limescale component is calcium carbonate and water generally has a high or medium hardness. The higher the PH level and temperature, the larger the quantity of limescale. Temperature has a great impact on limescale formation: for example, 80-degree water will leave six times more limescale than will 60-degree water. The settling of limescale on heating elements creates insulation that reduces their efficiency; it can even cause them to corrode, leading to direct damage.

    How Does the HydroFLOW Device Work?
    This limescale prevention method is based on the creation of randomly changing electric fields that are induced in the water and distributed throughout the pipe system. This leads to the formation of crystallized nuclei everywhere in the system. When the water is heated, the hard salts in the water (those which usually settle as limescale that builds up on the walls) grow as a suspension and are washed away with the water flow. The electric field that forms in the area of contact between the water and the pipe repels the limescale crystallized nuclei and prevents them from settling on the walls.

    The induction of the electric field is accomplished without intervention in the pipe system and is based on an accessory that is mounted around it. The electric field is transferred by the pipe system and water themselves. The impact of the process is continuous, independent of the water flow (yet the intensity of the field changes according to the intensity of the flow) and does not require the addition of chemicals.

    As a result of the high costs it had incurred from limescale damage to instant water heaters, British Gas conducted a long-range experiment in which it compared several limescale prevention devices. As part of the experiment, the method of action and structure of the devices were described. Only devices whose operation does not require the addition of chemicals to the water were tested. The experiment results revealed a clear advantage to the HydroFLOW devices: Systems in which they were installed became clogged after only 200 weeks or more, while all the systems treated by other devices became clogged within 40-100 weeks.

    HydroFLOW is different from other devices of its kind in terms of the following:
  • Its efficiency does not decrease in high temperatures.
  • It is also active when there is no flow in the system.
  • Its action is felt even at a distance from the area of the installation.


  • Enclosed with the opinion are the manufacturer's appendices, files and presentations describing the process and its effect according to the tests it conducted.

    Tests and Impressions Following the Use of HydroFLOW Devices in Israel
    WaterPath: The Water Association for the Beit Shean Valley:
    Contact person: Gadi Durchler
    A HydroFLOW device was installed in a pipeline, a water source with high hardness.
    At the beginning of 1996 a CUSTOM 26 device was installed in a 30" line. The device worked intermittently until November 2000. To meticulously test whether it was working, we opened a permanent window in two places. In the first window, we tested the limescale in two places: in the upper part of the pipe, there were no changes, probably because there is no water in this part of the pipe most of the time; in the lower part, we saw the following changes: at a distance of 1.2 km from the device, the data was identical to the measurements at the beginning, but there was no additional limescale.
    Below is data from the limescale thickness test conducted in the bottom part close to the device. Since the limescale settles in waves, we measured the limescale thickness in both the wide and narrow parts of the limescale wave (dimensions are in mm).

    Date April
    '96
    August
    '96
    June
    '97
    January
    '01
    March
    '04
    Thickness at the Peak of the Wave 76 55 40 36 43
    Thickness in the Narrow Part 40 30 24.5 32 41

    We can clearly see a decrease in the limescale thickness as long as the device is installed. We see an increase in the limescale thickness after the device is removed.

    Kibbutz Cabri:
    Contact person: Eitan Etzioni.
    Water is supplied to Kibbutz Cabri from the Cabri Springs. A CUSTOM 8" central device was installed in a system suffering from limescale damage due to high water hardness. The device is effective, the limescale deposits are brittle and wash through easily, crystallization was reported at the beginning of operation but it subsequently disappeared.

    Kibbutz Maabarot:
    Contact person: Akiva Doron
    A CUSTOM 8" device was effective in preventing deposits in heating elements and kettles.

    ELTA Ashdod:
    Contact person: Danny Arbel
    A CUSTOM 16" device was installed in a water spinning system in cooling towers. It was found to be effective, provided that the water quality is controlled, and that the towers are drained and fresh water is added on time. The conductivity and PH are continuously controlled.

    Okeanos, an Apartment Hotel at the Herzliya Marina:
    Contact person: Shlomo Gutman
    Three 6" units were installed there, as well as a separate unit for treating the boilers of 130 apartments (HydroFLOW C 60). Following installation, there is less limescale, and that which remains is brittle and washes through easily. Nonetheless, heating elements still burn out, and the reason for it is unclear.

    Dairy, Moshav Amka
    Following installation of a HydroFLOW HS 40 device, there was less limescale as well as a decreased incidence of algae in the drinking troughs (probably because it prevented the roughness that is formed by the limescale and which constitutes a breeding ground for algae). Note: The cowshed is not currently operating.

    Kibbutz Dalia, Central Hot Water Supply System:
    Contact person: Tuvia
    A new HydroFLOW HS 40 device was installed after a previous installation in the pen had made a positive impression. Here, too, it was reported that the device had prevented limescale and algae growth in the drinking troughs.

    The Israel Electric Company, Energy Center at the Haifa Power Station:
    Contact Person: David Lovaton
    Six 60C HydroFLOW 2" devices prevent limescale deposits.

    Moshav Regba, Water Supply System in Private Homes:
    Contact person: Amnon Eshel
    170 installed devices proved effective, putting an end to replacement of heating elements as well as blockages in showers.

    Summary and Instructions for Integrating the System
    As it was pointed out at the beginning, the theoretical background and the research carried out by British Gas Company indicate a device that can contribute greatly to the prevention of limescale in hot water systems. The test that was conducted by those in charge of water systems in Israel where HydroFLOW devices had been installed indicates virtually overall satisfaction: The devices prevent limescale and reduce the damage it causes, even under local conditions. All this makes it possible for us to recommend using this technology even in the hot water systems
    of Pazgas.

    Nevertheless, the limitations of the device and the users' impressions of it have led us to establish the following guidelines for installing it
    in Israel:
  • One should avoid installing the device in places where saline water
         without desalinization is used, such as places in the Arava. Due to the
         limitations of the device, its benefits there will apparently be limited.
  • One should focus on installations in which the water is especially
         hard. These are places where most of the water supply comes from
         drilling, and less from the national carrier. Nevertheless, the relatively
         high PH of the carrier water and its hardness justify installation of
         limescale prevention systems even in this water.