Monday, January 10, 2011 1:38 PM
Knowledge Center


Q1. What is Hard Water?

When water is referred to as 'hard' this simply means, that it contains more minerals than ordinary water. These are especially the minerals calcium and magnesium. The degree of hardness of the water increases when more calcium and magnesium particles are dissolved.

Magnesium and calcium are positively charged ions. Because of their presence, other positively charged ions will dissolve less easily in hard water than in water that does not contain calcium and magnesium.

Q2. What do you mean by scale?

Water has many dissolved solids in it. The salts of calcium and magnesium are called the hard salts. These salts precipitate with the increase in temperature and leave a white deposit on the surface of the exchanger tubes. This white salt deposit is termed as scale, which acts as an insulator and prevents the transfer of heat.

Q3. Why Scale Guard?

It is a non-chemical online type scale preventor, which does not require any chemical. It works with a combination of adsorption, turbulence & galvanic action. Inner core converts the hardness salts into colloidal particles. Absolutely no recurring, operating and maintenance cost are involved.

Q4. How does Scale Guard work?

Working of Scale Guard can be explained in the following 4 steps:

  • Adsorption of H+ ions by the special metal alloy core.
  • There is an increase in the pH value in the next layer of water.
  • With the increase in pH the solubility of water goes down.
  • When the solubility of water goes down the precipitation of hardness salts of Calcium and Magnesium begins.
  • This precipitation is broken down into colloidal particles due to turbulence.
  • These colloidal particles are very small in size about 0.01µ to 0.05µ. They remain suspended in the water in an interform. The water can thus pass through the system over the heat exchange surfaces, without depositing lime scale.

Q5. What are the advantages of Scale Guard?

  • Prevention of scale and removal of existing scale.
  • No extra electricity consumption.
  • Saves energy due to no scale formation.
  • No chemicals required, hence no recurring cost.
  • No corrosion risk.
  • No extra manpower required for maintenance.
  • No pollution.
  • 5 years replacement warranty.
  • Comprehensive after sales service.

Q6. What are the application areas of Scale Guard?

  • Air-conditioning plants: for condenser and chiller units
  • Cold storage and refrigeration
  • DG sets: water-cooled DG sets also face-scaling problem
  • Injection moulding machines
  • Heat Exchangers
  • Evaporating condensers
  • Dye-casting machines
  • Compressors
  • Vacuum pumps

Q7. How does Scale Guard conserve energy?

Water has many dissolved hardness salts of calcium and magnesium in the form of carbonates and bicarbonates. These salts precipitate with the increase in temperature and form scale deposits inside the exchanger tubes. This scale acts as an insulator and prevents the proper transfer of heat. As water flows through the Scale Guard a combination of pressure changes, turbulence and galvanic action causes the dissolved scaling salts to be precipitated as fine (colloidal) particles. These colloidal particles remain suspended in water in an interform. The water can thus pass through the system and over the heat exchange surfaces without depositing lime scale. Hence upto 10% of the electricity can be conserved through the prevention of scale formation.

Q8. How does scale guard eliminate the existing scale in exchanger tubes?

Scale Guard breaks the hardness salts of Calcium and Magnesium into fine colloidal particles of size 0.01 to 0.05µ. These colloidal particles while flowing over the surface of the exchanger tubes erode the existing scale particles. Hence, the layer of scale diminishes with the passage of time.

Q9. How does it save electricity and how much?

We have an electricity savings chart wherein we do the calculations according to the plant capacity, working hours/day/year and electricity charges @ ../kW say for example client has 150 TR A.C. plant. After calculations we found out that he can save electricity worth Rs.1, 53,000/- annually, which is a good saving. So investment in Scale Guard is a wise decision. (See home page to find out electricity saving with Scale Guard)

Q10. Calculations required arriving at a suitable model guard

We have a model selection chart wherein we calculate the flow rate according to the capacity of the condensers etc. With the help of flow rate we determine the pipe size, length, weight and select the model.

Q11. When do you say the water is soft or hard depending upon ppm of the salts?

Hard water is water that contains dissolved hardness minerals above 1 grains per gallon (GPG). GPG is a weight measurement, which is equal to 17.1 ppm (parts per million). Hence if the hardness minerals like calcium, magnesium and manganese is less than 17.1 ppm in water then the water is soft otherwise hard.

Q12. What is the process involved in a chemical water treatment system?

A chemical treatment system like water softening involves the interchange of one hard ion (calcium) for another soft ion of like charge (sodium) in the resin. Hard water is passed through a bed of resins containing sodium ions, which are exchanged with calcium ions in water. Thus the water is softened.

Q13. How does adsorption of H+ ions from water occur in scale guard & doesn’t it affect chemical composition of water?

Scale Guard has a special metal alloy core, which has an overall negative charge. The water molecule has got one H+ ion and one OH- ion. The H+ ion owing to its positive nature is attracted towards the core, which is negatively charged. Hence we say that the H+ ions are adsorbed on the surface of the core.

On the contrary we also have an alternate layer of OH- ions. In this layer of water, the pH goes up and the water becomes alkaline since pH=1/ log [H+]. This sudden increase in pH causes the precipitation of Calcium and Magnesium carbonate salts. Once the precipitation has taken place, the core brings the pH to normal by releasing the H+ ions. Hence we say that the chemistry of water is unaltered when the water leaves the Scale Guard.

Q14. What’s the time taken to install Scale Guard and what is the pressure drop observed after installation?

It takes 1-2 days to install Scale Guard. This is mainly dependent on the geography of the site like the height of water line & size (dia.) of water line in which Scale Guard is to be installed. However, if it’s a project then the time required to drain the water from the pipelines is saved, which normally takes 5-6 hrs. The pressure drop is minimal say 1-2 psi after the installation of Scale Guard, which is negligible.

Q15. Describe the role of condenser, compressor and Pump in the cooling circuit. Criteria required for installing scale guard.

A central air conditioning system that needs to cool and dehumidify uses a condenser, evaporator coil, and refrigerant piping to operate. The refrigerant is compressed in the compressor and run through a series of tubes inside the condenser to remove as much heat as possible, then piped to an evaporator coil as a warm liquid. Expansion of the compressed liquid causes it to cool, and as the air passes over the coil, heat is extracted. The cool liquid becomes a cool gas as it gathers heat from the air, and is drawn back to the compressor to start the procedure again. The pump is only meant to force the water from cooling tower to the condenser and back to cooling tower.

The criteria required for installing Scale Guard is that at least 75% of the volume of water flowing in the cooling circuit must come in contact with Scale Guard to be able to be treated.

Q16. Explain Reverse Osmosis.

To understand Reverse osmosis let understand the term osmosis. Osmosis is the "movement of a solvent through a semi permeable membrane (as of a living cell) into a solution of higher solute concentration that tends to equalize the concentrations of solute on the two sides of the membrane. In reverse osmosis, the idea is to use the membrane to act like an extremely fine filter to create drinkable water from salty (or otherwise contaminated) water. The salty water is put on one side of the membrane and pressure is applied to stop, and then reverse, the osmotic process. It generally takes a lot of pressure and is fairly slow but the water is pure.

Q17. Where should the sample water for testing should be collected from & how computer simulations help you in arriving at the quality of water?

Sample water has to be collected from the site itself. The computer simulation Helps in checking the performance of scale Guard unit. Once the complete analysis of raw and recirculated water are fed into computer, the programme gives the behavior of water at different stages. For the perfect working of Scale Guard, the Super Saturation Ratio (Sr) at Scale Guard should be higher than Sr at condenser. Calculated Hardness (Hc) in cooling tower should be equal to actual hardness (Ha) in an ideal condition with a margin of 10 ppm. When Hc-Ha>+20 ppm we can< observe that the Scale Guard unit is not working satisfactorily.

Q18. What after sales service do you provide?

Scale Guard technical advisors are trained and continually informed about the results obtained in various applications. This entails analyzing the water periodically and making visual inspections of the plant which is being protected by Scale Guard. Should adjustments be necessary the appropriate measures will be taken together with the customer.

Q19. Will the equipment rust or perform abnormally with time?

Equipment would not rust as it is made from special stainless steel. We have already taken a five year replacement warranty. After five years if there is disruption in the smooth working of SG concerned dept/company have to opt for a new Scale Guard.

Q 20. Why do I need a Scale Guard as I have already installed a water softener?

For raw water generally softening plant is used to reduce the hardness, but this hardness increases in the re-circulating water due to evaporation and heat exchange that takes place in the circuit of the cooling tower
It is essential to treat re-circulating water as this is the water which goes to the chillers/condensers
The condenser is the heart of a chiller’s mechanical system so we need to protect them at any cost.

Q21. If I can use the water for drinking, why this cannot be used for AC plant

For drinking purposes, water need to be clear and bacteria free, while hardness can be upto 600ppm. In case of centrally AC plant water hardness should not be 10 ppm i.e why water treatment is necessary, even or drinking/corporation water to avoid scale formation

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