DuraGuard™ - For Cooling Towers

DuraGuardCooling Towers are a very important part of many ch emical plants, power plants and process plants. Mechanical draft towers are widely used in industry which utilize fans to force or suck air through circulated water. Usually there are several problems in cooling towers as detailed below.

Corrosion

Cooling tower frames, water inlet & outlet pipes, f an assembly consists of top / bottom hub plate, hub spool, clamps, & taper bush are made of carbon steel. These components get corroded due to high humidity & warm conditions obtaining at coolin g tower systems. Also ozone and other polluting gases in the surrounding atmosphere is th e major cause of corrosion.

Microbiologically Induced Corrosion (MIC)

Cooling water system offers a favorable environment for the growth of microorganisms. Microbiological growth on wetted surface leads to f ormation of biofilms. These cause fouling. Microbiological fouling is the result of abundant g rowth of algae, fungi and bacteria on surfaces. MIC is the result of availability of organic & inor ganic nutrients, factors such as temperature, normal pH range and continuous aeration of the cool ing water. Wood used in cooling towers deteriorate due to chemical, biological & physical causes.

Duraguard video

Duraguard™ - Surface Protection System

Duraguard™ is a unique process. It uses Dimple’s four innovative chemicals in two-stage process as under:

Stage I: Cleaning

  • Duraclean: Surface preparatory agent

Stage II: Coating

  • Duramix 1: A Blend of Ceramic Ironite, Active Ceramic & Cem ent
  • Duramix 2: Water miscible modified Epoxy Resin
  • Duramix 3: Modified Epoxy Hardener

Detailed working of Duraguard™ System is described below:

Surface Preparation

This involved use of patented process technology (E uropean Patent No – EP 1888815B & Indian Patent No – 224346) of Duraclean (a specialized org anic polymer) as corrosion removal/inhibition.

Duraclean converts oxides on surface into docile fo rm. By this conversion, burr (oxides) on surface, if not docile oxide, can be cleaned below 50 microns. Growth of oxides is always in mathematical progression hence lesser the burr on s urface lesser is the rate of corrosion. Also bio & bi-metallic corrosion is controlled by Duraclean. Such method of surface preparation eliminates process like shot blasting, which is not eco-friend ly. Shot blasting embeds some oxides into mother metal, which later erupts from the surface a nd cracks the protective film built on top.

Protective Coating

Duraguard™ is a 3-pack system for providing complet e solution for long-lasting corrosion control and giving the surface effective chemical resistanc e. Two coats of Duraguard™ are given by mixing Duramix 1, Duramix 2, and Duramix 3 & water in predefined ratio.

  • The unique combination of surface preparation, ble nd of ceramic ironite, puff ceramic cement & modified epoxy gives complete resistance to chemi cals.
  • This coating also gives better corrosion, abrasion & UV resistance as compare to acid resistance paint.

Key Features of DuraGuard

  • Excellent Corrosion Resistance
  • Resistance to electricity
  • Excellent resistance to chemicals like H 2 SO 4 , NaCl, NaOH
  • High abrasion resistance
  • Welding can be done after coating
  • Excellent UV stability
  • Strong adhesion on many material of construction
  • Resistance to cathodic disbondment
  • Ability to withstand high temperature variation
  • Resistance to Microbiologically Induced Corrosion (MIC)
  • Providing effective moisture barrier
  • Resistance to development of pinholes
  • Monolithic coating
  • Anti-rodent properties

Properties of Duraguard™

Properties Test Standard Unit Limit Observation
Scratch Hardness with 1.5 Kg load IS 101 Part 3 / Sec. 2 Visual No such scratch to show bare metal Passes
Abrasion Resistance (CS17 wheel, 1 Kg load, 5 , 000 revolutions ASTM D 4060 Weight loss in grams 0.3 grams max. 0.0845
Impact resistance with 1.814 Kg load & 100.25 cm Height ASTM D 2794 Nm Minimum 2.8 4.448
Chemical resistance ASTM D 543 Visual Shall not show any sign of blistering, wrinkling & lifting of the film Passes
Adhesion ASTM D 4541 MPa   2.6
Corrosion accelerated Salt spray in solution of 5% NaCl, 0.26 gm/ltr CuCl 2 and pH 3.1 to 3.3 ASTM B 117 Hours 72 72
Salt spray test ASTM B 117 Hours 2,000 2,000
UV Resistance test   Hours 500 500

Comparison of DuraGuard with Epoxy Painting

Parameter Epoxy Paint Duraguard™
Salt spray test at 5% c onc entration of NaCl. 96 Hours 2,000 Hours
Corrosion accelerated Salt Spray (CASS) in solution of NaCl 5%, CuCl2 0.26 gm/ltr and pH 3.1 to 3.3 by Acetic Acid. Not specified 72 Hours
UV Resistance Not specified 500 Hours
Abrasion Resistance Not specified Weight loss of 0. 0845 grams after 5,000 rev. of CS17 wheel
Impact Resistance Not specified Withstand 4.448 Nm force
Acid / Alkali Resistance Up to 25% Concentration Gives resistance to 1.800 & 1.280 Sp. Gravity H 2 SO 4 At 60 O C for 24 Hours
Hard Drying 14 Hours 4 Hours
Overcoat time 12 Hours 3 Hours

Case Study of Cooling Tower in Power Plant

Based on the extensive trials and commercial applic ation in the cooling tower section of the power plant the results achieved by Duraguard™ clearly in dicates improvements as captured below

  • Duraguard™ gives 3 times protection life as comp ared to epoxy paint for steel structures, fans & water Inlet / outlet pipes in cooling tower.
  • Duraguard™ eliminates formation of microorganism like algae, fungi, bacteria for 3 years.
  • Life of wood fills is increased by Duraguard™ .

Duraguard™ Application Photos:

Condition of the pipe before Condition after treatm ent
Condition-of-the-pipe-before Condition-after-treatment
Condition of the hub spool before Condition after t reatment
Condition-of-the-hub-spool-before Condition-after-teatment
Condition of the Clamp before Condition after treat ment
Condition-of-the-Clamp-before Condition-after-treat
Condition of Hub Plate Condition after treatment
Condition-of-Hub-Plate Condition-after-treatment-5

Copyright 2020