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Weldon Engineers, India

Weldon Engineers, IndiaWeldon Engineers, IndiaWeldon Engineers, India
Weldon Engineers, India

Round FRP Cooling Tower

Rectangular FRP Cooling Tower

Electrostatic Scale Preventer - SCALE OFF

Non Chemical Water Treatment Equipment

Weldon Engineers, India
Home » FAQ


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 off?
It is a non-chemical online type scale preventer, 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 Scale off work?
Working of Scale off can be explained in the following 4 steps:

Adsorption of H+ ions by the special metal alloy core.
Q5. What are the advantages of Scale off?
Q6. What are the application areas of Scale off?
Q7. How does Scale off 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 off 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 off eliminate the existing scale in exchanger tubes?
Scale off 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 at per 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 off is a wise decision. (See home page to find out electricity saving with Scale off)

Q10. Calculations required arriving at a suitable model Scale off ?
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 off & doesn't it affect chemical composition of water?
Scale off 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 off and what is the pressure drop observed after installation?
It takes 1-2 days to install Scale off. This is mainly dependent on the geography of the site like the height of water line & size (diameter) of water line in which Scale off 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 off?
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 off is that at least 75% of the volume of water flowing in the cooling circuit must come in contact with Scale off 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 off 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 off, the Super Saturation Ratio (Sr) at Scale off 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 off unit is not working satisfactorily.

Q18. What after sales service do you provide?
Scale off 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 off. 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 Scale off concerned dept/company have to opt for a new Scale off.

Q20. Why do I need a Scale off 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 sc.

Frequently Asked Questions About Electrostatic Water Treatment

Q1. What is it?
Electrostatic water treatment is a method of conditioning water using the physical and electrochemical effects of electrostatic fields to cause the formation of tiny (colloidal) particles. Essentially it is a method of deposit control.

Q2. How does it work?
By applying dc voltage to a submerged electrode we form a local capacitor within the water, the piping system or treatment rack wall. Ions of calcium, magnesium and bicarbonates are brought together in the bulk solution to form colloidal particles which are then in a stable form not subject to plating out or forming deposits within areas subject to the full flow of treated water. These ions are moved from solution to suspension in the bulk water.  This change allows the water to dissolve existing scale deposits.

Q3. Does the electrostatic treatment system kill bacteria?
No, however the Electrostatic Scale-off system is bio-static. That is by changing the condition of the water, and allowing a natural rise in the pH and the presence of chlorine in municipal water supplies bacterial development is contained at or below industry standards.  Most bacterial prefer to live in an environment in which the pH is 8 or below.  Normally, the pH in a escale-off treated system will be above-8.5. 

Q4. Does the electrostatic treatment cause corrosion?
No. The electrostatic field cannot cause corrosion because there is no electron transfer as a result of the electrostatic treatment. Once scale, sludge and bacterial deposits are removed from the system, corrosion normally caused by these deposits will be controlled as well.

Q5. Do I need to continue testing my water?
Normally, the only water test required for a SCALE-OFF treated system is to monitor conductivity and pH.  This eliminates many other time consuming tests that are required with chemically treated applications. A computer simulation report shall be submitted after every water test reports for evaluating performance.

Q6. Can I eliminate tower bleed altogether?
No, While it is possible to operate cooling towers at higher levels of conductivity, continued bleed of the system is necessary to keep concentrations of particulate matter at appropriate levels. Water use and discharge fees will be reduced as a result of operating at higher conductivity levels. Except in special conditions the normal and proper operation of a tower will involve bleeding or blow down to maintain the water conductivity at between 3200 and 3800 ms/cm of conductivity.

Bleed off in cooling tower bottom : A bleed is set for following months:
Q7. Will old deposits of scale be removed?
Yes, old deposits will be loosened and dissolved slowly. In one case the SCALE-OFF system was responsible for removing over 60,000 pounds of scale that had developed in a cooling tower.  It had taken over 15 years for the scale to accumulate in this tower and it took only one operating season for the Electrostatic scale-off to remove these massive deposits.  However, if the deposit is sufficiently thick so that it can cause a loss of heat transfer efficiency or interfere with flow efficiency it should be cleaned before startup. We recommend starting with a clean system.

Q8. How much power does the electrostatic system use?
Not Much, the operation of the SCALE-OFF system consumes about the same power required to operate a 7 watt night light.  That consumption represents pennies per day of operating cost.

Q9. Are there any safety hazards in using an electrostatic treatment system?
No,  The SCALE-OFF system has been designed to provide the utmost protection to those who may work with this innovative fluid treatment process.  The finest materials and manufacturing techniques are employed to build our products.  The potential for hazardous shock is less than one would normally experience working with a typical household appliance.

Q10. Can Chemical treatments be eliminated or reduced?
Yes, in most cases the chemical treatments used to control scale, bio-fouling and corrosion are eliminated.  Since cooling towers are massive air scrubbers, the total elimination of chemical additives may be related to the location of the tower, local water quality and the condition of the tower and related equipment.

The elimination of chemical additives for boiler applications and other process water treatment is dependent upon many other variables. While total elimination may not be possible a dramatic reduction of chemical requirements for treating these applications is the normal.

Why do I need the Electrostatic scale-off System?
The most important reason is because of the increased cost of fuel and water. It is becoming increasingly important to maintain scale-free equipment systems to minimize energy loss. Scale buildup on heat transfer surfaces can reduce heat transfer by 20% or more, cutting efficiency by more than 25%.

The Electrostatic scale-off is also 100% environmentally friendly and meets all EPA requirements. The Electrostatic scale-off System will prevent scale buildup, maintaining clean surfaces for maximum thermal transfer in heating or cooling systems.

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