Using the Strengite Process to Clean a Heavily Fouled Glycol System at The British Museum
The condense chilled water system at the British Museum was treated with antifreeze to protect the system from freezing damage. Regretably the antifreeze had become acidified by bacteria and became highly corrosive. Acidified glycols are well known for having corrosion rates up to nearly 1000 times greater than normal. Severe damage to pipework can occur in short time periods. In most regions, antifreeze is not allowed to be discharged to drain. Expensive tankering way of the system water to disposal is required. The lost glycol has to be replaced at the end of the cleaning. This is both costly and has a large carbon foot print of three kilos of CO2 released per kilo of antifreeze added. Cleaning of corroded closed loops treated with antifreeze is more costly and difficult than cleaning standard closed loop systems.
A Low Oxygen Corrosive Environment
The British Museum condensor system contained 10.3% monoethylene glycol. The system volume was 10,400 litres. The system pH varied between 5.6 to 6.1 depending upon where sampled. The system was left under acidic conditions for approximately one year. Severe corrosion had occurred in spite of a low oxygen enviroment being present. Samples taken from the system would initially appear clear with a slight black tinge but when left for a few hours, the presence of oxygen in the air changed the oxidization state of the dissolved iron and the samples turned an opaque orange/brown colour. The magority of the pipework was made of iron and steel.
Cleaning Up the System Without Discharge or loss of Glycol
The Strengite Process was used to clean this system without discharge. The antifreeze within the system was not lost. The cleaned up system water was pH adjusted to between pH 8.1 and had a final iron level of below 0.2 ppm. The final copper level was below 0.2 ppm.
It is possible to directly calculate the amount of corrosion removed by a Strengite Process clean. Approximately 48 kg of rusts were removed by this cleaning. This equates to an iron level of 3345 ppm iron released during the clean. Traditional cleaning methods rarely go above 1000 ppm iron and would have required three cleanings to achieve this result. The Strengite Process achieved this in a single clean. Approximately 312,000 litres of water consumption and pollution were avoided.
The entire cleaning and removal of contaminants took aproximately 10 days.
The Strengite Process successfully recovered 1071 kg of antifreeze and prevented 3.2 tons of CO2 emissions. Additionally it avoided a large tanker based disposal cost. It avoided consuming and pollution 312,000 litres of water. The Strengite Process clean removed many times more rust than alternative cleaning methods. It suppressed iron solubility post cleaning even when rust deposits still remained within the system.
The Strengite Process is a better way to clean closed loop systems.
The Strengite Process is a patented process. The technology, equipment and products for the Strengite Process are only available to licenced and trained water treatment specialists who operate to a high standard and skill level.
The Dawn of Effective Buffer Tank Cleaning With Zero Discharge: A Case Study of Using the Strengite Process to Clean a 90,000 Litre Buffer Vessel
The cleaning of large buffer tanks is notably difficult due to the inability to achieve rapid water velocities across metal surfaces. Physical cleaning, filling, and emptying vessels provides marginal cleaning at best and consumes signficiant amounts of water. Mill scales created during metal fabrication are not removed. Chemical cleaning is more effective but typically requires the consumption and pollution of ten times the volume of the buffer vessel. Buffer vessel cleaning tends to be time consuming with cleaning times of two to five weeks not uncommon.
A New Way Forward
A 90,000 litre steel buffer vessel was installed at County Hall, Leicester as part of a district heating system. Prior to being put into use, the Strengite System was used to clean the vessel without any discharge. This saved and avoiding polluting 900,000 litres of water. Approximately 17 kg of rusts were removed by the cleaning. Cleaning times were equal to or shorter than alternative methods. All flash rusting issues were avoided. Over 1 ton of CO2 emmissions were avoided.
The Strengite Cleaning
Initally 200 litres of Strengite C1 cleaner was added and circulated for three days. The water was unheated (March temperatures). After three days, the pH had risen to 5.4 indicating that approximately 95% of the cleaner had reacted with 17 kg of iron oxides (equivalent to a dissolved iron level of 500 ppm).
The Strengite equipment was then set up and the precipitation phase of the cleaning begun where the dissolved contaminants are forced out of solution and separated by filtration. The Strengite equipment is designed to enable rapid and easy changing of filter bags and avoid water loss.
During the initial precipitation phase, 50 filter bags (1 micron) were used over two and a half days. This was then followed by the polishing phase where a further 96 filter bags (1 micron) were used. The resulting water was found to have dissolved iron levels below 0.5 ppm (the limit of detection of the on site field test kit) and was completely clear.
The entire cleaning and removal of contaminants took 10 day working days. Notably no flash rusting was observed during the removal of the cleaner and is a design feature of the Strengite Process. There was no discharge. The filter bags consumed during the cleaning were cleaned off-site for reuse in future using a process that also avoids discharge.
The Strengite Process offers a better way to clean buffer vessels that not only avoids discharge and protects the environment, but which also delivers effective vessel preparation to enable decades of trouble free use.
Strengite Process Equipment
Case Study of Using the Strengite Process to Clean a Heavily Rusted Glycol System Without Creating Discharge
Antifreeze water mixtures containing monoethylene or propylene glycols are widely used to prevent freezing in closed loop systems. These mixtures are not corrosive to system metals provided that a suitable corrosion inhibitor package is maintained and bacteria growth is prevented. Typically, a minimum concentration of glycol above 25% is maintained to prevent the growth of bacteria. In the event that the glycol concentration falls below 25% or biocide levels are not maintained, bacteria growth can rapidly occur and acidify the glycol. When this happens, corrosion rates approaching thousand times above previous corrosion rates can occur. Severe damage to pipework can occur in short periods of time.
In most regions, waste antifreeze is not allowed to be discharged to drain. Additionally, acidified glycol dissolves copper. In most regions, the discharge limit of copper is 3 ppm. Very little copper has to dissolved before the system glycol mixture violates copper discharge rules. System copper levels many times above the discharge limit are not unusual. Expensive tankering way of the system water to disposal is required. The lost glycol has to be replaced at the end of the cleaning. This is both costly and has a carbon foot print of three kilos of CO2 released per kilo of antifreeze added.
To make matters worse, the disposed glycol/water mixture often still has most of the original glycol present and represents a loss of resources. Current closed loop methods require the flushing out of systems with fresh water that is approximately ten times the system volume at the end of chemical cleaning. This is to remove all traces of the released corrosion productsand cleaners. The total loss of the glycol is unavoidable.
Cleaning of corroded closed loops suffering from degraded antifreezes is expensive, more difficult, and has a much greater negative environmental impact than cleaning standard closed loops systems.
The Strengite Process was developed to enable the cleaning of corroded closed loop systems without discharge. The process is a significantly departure from current cleaning technologies. The Strengite Process, like current chemical based cleaning chemistry, first dissolves corrosion deposits, but instead of discharging the resulting mixture to drain, the new process is able to modify the chemistry to precipitate the dissolved contaminants. The precipitation and filtration out of the contaminants takes places within specially designed equipment to prevent the release of solids throughout the system. The large numbers of fine particles created during precipitation have a vast surface area, absorb oils and greases, and lead to their removal from the system water. The system water at the end of the Strengite Process has exceedingly low levels of dissolved metals such as iron and copper - often below 0.1 ppm. The cleaned up water still contains some cleaner residuals but by addition of specially formulated corrosion inhibitor products, fully functional corrosion inhibitor packages that offer excellent corrosion protection are assembled.
The cleaning system uses the same physical and operational approaches that standard closed loop cleaning uses except water is not discharged to drain but rather cleaned up and returned to the system.
The Strengite Process’s chemistry is targeted towards dissolving and then precipitating dissolved corrosion deposits. It does not effect ions such as molybdate. This is highly useful. Molybdate represents most of the chemical cost of many corrosion inhibitors and also has a finite supply. By leaving molybdate untouched, the Strengite Process opens the door to infinite cycling of molybdate within closed loop systems even if they are repeatedly cleaned.
The Strengite Process chemistry creates conditions that cause the solubility of ions such as copper and iron to fall to near zero even if corrosion inhibitors such as molybdate/nitrite are present within the system. Many will be familiar with the problem of installers doing further work on systems after what was supposed to be completion. The resulting contamination often raises copper and iron levels beyond specification limits. Up to now, the only solution has been to dump the system and start again. The Strengite Process enables the removal of the unwanted copper and iron ions, avoids discharge, and leaves the corrosion inhibitor system intact. There is no need to retreat the system with corrosion inhibitors.
A System with Extreme Fouling
At Specsaver’s Headquarters in Whitely, England, the chilled water system contained four percent monoethylene glycol. It had become acidified and serious corrosion had occurred. The system volume was 2350 litres. Only the risers of the three story building were iron piping with the rest of the pipework largely plastic pipe. All of the 141 fan coil units were heavily fouled to the point that little cooling of the building was possible in spite of a new chiller being installed only a few months previously.
The system water carried a heavy load of rust with a total iron level of 4500 ppm. Filtering through 1 micron bag filters did little to reduce the iron load.
A New Way Forward: Cleaning the Impossible with No Discharge
The Strengite Process was used to clean this system without discharge. The antifreeze within the system was not lost. The cleaned up system water was pH adjusted to between 8.5 to 9.0 and had a iron level of below 1 ppm.
Approximately 38.7 kg of rusts were removed by the cleaning. This equates to an iron level of 11,914 ppm iron released during the clean. Traditional cleaning methods rarely go above 1000 ppm iron and would have required twelve cleanings to achieve this result. The Strengite Process achieved this in a single clean. 282,000 litres of water consumption and pollution were avoided.
X-ray analysis of the pipework indicated that approximately 43 kg of iron had corroded from the pipework. Sixty five percent of the rust was removed by the cleaning. Spalding from incomplely cleaned surfaces usually leads to problematic high dissolved iron levels. This did not occur because the Strengite chemistry surpresses iron solubility. Iron levels remained below 1 ppm even when sediment remained in the system water.
The entire cleaning and removal of contaminants took aproximately three weeks and included cleaning and flushing all the fan coil units and strainers which were very heavily fouled.
A by-pass filter was installed on the system to remove corrosion deposits as they erode from pipe walls over time. The iron level continues to remain low months after the cleaning.
The Fate of the Collected Waste
The contaminants removed from the system were collected on filter bags. These bags could have been simply disposed of to the normal rubbish, but the decision was made to clean them up. The bags were washed and made available for reuse in future cleanings. This created a few hundred litres of water waste which contained all the removed system contaminants. The water waste was allowed to settle.
This produced a large layer of clear water that was drawn off and pH adjusted prior to discharge. The mucky bottom water was mixed with cement and allowed to further settle. The result was clear water on the top of the hard settled solids. The clear water was drawn off and pH adjusted prior to discharge. All the discharge water was tested for copper and found to have below 0.1 ppm total and soluble copper. The resulting dry solids were disposed of as cement waste at the local tip. Overall, compared to the volume of discharge water that standard chemical cleaning would have created, a reduction of greater than 99.99% in waste volume was achieved.
New Tools for Our Industry
The Whitely fouled glycol system was one of the most fouled closed loop systems that any of us had ever encountered. It represents an extreme example of closed loop cleaning. If current chemical cleaning methods had been used, the works would have failed. The level of fouling would have been too much to clean in any practical way. Iron transport and return to high levels of soluble iron would have fouled the newly installed chillers. There would have been little alternative but to re-pipe all or part of the system at considerable cost. Instead the Strengite Technology enabled the system clean-up in a straightforward manner while avoiding the creation of large amounts of costly to dispose of waste. All the original system glycol was preserved and able to be reused.
The Strengite technology has been used on other less difficult systems such as large buffer vessels and other building closed loop systems. Millions of litres of polluted water waste have already been avoided by use of the technology.
Strengite Process Equipment
A Case Study of Using the Strengite Process to Precommissioning Clean Two Closed Loop Systems at Astra Zeneca Macclesfield
Precommission cleaning of closed loop systems is necessary to insure short and long term smooth system operation. Failure to correctly clean systems can lead to fouling of heat exchange surfaces, poor valve operation, higher energy costs, and a wide range of other problems. Good precommissioning cleaning should remove debris, oils/greases, corrosion films such as rust, and mill scale created during pipe formation. The standard method for precommission cleaning of closed loop systems is to introduce a cleaner and circulate for a period of time. This solubilises oils/greases and strips any corrosion/mill scale from the pipework. The resulting solution is then flushed to drain using a continious fill and drain method. Typically at least ten times the system volume is flushed to drain to completly the removal of the released contaminants. The process of cleaning causes metal ions such as copper, lead (from solders), and zinc to be dissolved, and transferred to the waste water. The discharge limit for copper and zinc is normally only 3 ppm. The process of cleaning closed loop systems virtually always breaks discharge regulations by many times over. It is not unusual for closed loop cleaning to create dissolved metal levels of over 1000 ppm. Closed loop cleaning is the largest source of toxic heavy metals to the sewage system. Alternative closed loop cleaning methods that do not create discharge rely solely on water velocity and filtration to remove corrosion films/deposits. They do not use chemical cleaners to clean pipe work surfaces. These methods are incapable of removing any corrosion or mill scale from pipework. This often leads to problems when systems become operational.
A Challenging Cleaning Requirement
Astra Zenica at Macclesfield installed an extension to their syringe filling line. This required extending both the chilled water and the low temperature hot water systems. The production area lacked a flushing water supply or a flushing drain. Additionally a cleaning process that could be operated without mess or disruption was required. The systems needed to be cleaned to a high specfication. All corrosion products, mill scale, oils and greases needed to be removed. The combined volume of both systems was between 2000 to 3000 litres. Cleaning the system using any of the standard or alternative closed loop cleaning methods would have been either impossible, or would have failed to clean the system sufficiently.
The Strengite Process: High Quality Closed Loop Cleaning Without Discharge
The extensions to the chilled and heating systems were connected together and cleaned as one system. The Strengite Process was used to clean the combined water system as it could deliver a high quality precommissioning clean that removed corrosion deposits, mill scale, oils and greases without discharge. Strengite C5 cleaner was introduced to the system and circulated for several days for cleaning action to occur. After this, the Strengite equipment was set up on a side stream to the system. Strengite’s Pink Purity product was then injected within the Strengite equipment to cause dissolved contaminants such as iron and copper to come out of solution. These were then directly removed by simple filtration within the Strengite equipment. Multiple water passes were made through the Strengite equipment with a further precipitation polishing product added to aid removal of fine contaminant particles. The system water was then pH adjusted to 7.6. A specially designed corrosion inhibitor product which builds upon the ions that remain in solution at the end of the Strengite cleaning was then added. Final water samples taken 10 days after the clean had iron levels of 1.8 ppm ppm total iron and 0.7 ppm soluble iron. The copper levels were < 0.2 ppm total and < 0.2 ppm soluble copper. Throughout the entire Strengite cleaning process there was no consumption or discharge of water. In total 20,000 to 30,000 litres of water supply and pollution was avoided.
Soluble metals become insoluble and are removed on filter bags.
The Strengite Process offers a more sustainable way to clean closed loop systems without water consumption or pollution. The Strengite Process is a patented process. The technology, equipment and products for the Strengite Process are only available to licenced and trained water treatment specialists who operate to a high standard and skill level.
Strengite equipment used to clean the system.
Removing Soluble Iron from Closed Loops: A Case Study of Using the Strengite Process to Remove Soluble and Total Iron from a Live Chilled Water Systems
It is not unusual for closed loop systems to become fouled with excessive soluble and insoluble iron and copper. This can be caused by system deteriation, changes to the systems, or bacteria infection. All negatively effect the system operation and increase the energy to run the system. The standard solution is to flush the system out with fresh water until the water is clear of soluble and insoluble metals. This means losing all the chemical treatment within the system. Typically it will require a water supply and drainage capable of replacing the system volume ten times over. This is both wastes clean fresh water and creates water pollution. Closed loop flushing is considered to be the largest source of heavy metals such as copper, lead, and zinc to the sewage system. In many areas, the discharge will require a discharge permit.
A Chilled Circuit with Excessive Iron Levels
Heckfield Place in Bothey Spa, Hampshire had a chilled water circuit that was fouled with excessive levels of soluble and total iron. The site needed to clean this system, but lacked a water supply and drainage that could be used to flush the circuit. The chilled water system had a volume of 2000 litres. Iron levels were 100 ppm total iron and 41 ppm soluble iron. Copper levels were 0.6 ppm total copper and 0.3 soluble copper. The site did not want to undertake a clean of the metal surfaces within the chilled water system.
Left bottle was the starting sample. Middle sample was taken during the cleaning, and the right bottle was the final sample.
Removing Soluble Metals without Discharge
The Strengite Process was used to clean up the water within the chilled water systems without discharge and without taking the systems off line. This was achieve by operating the Strengite Process so that approximately four to six system volumes were passed through the Strengite equipment. The Strengite Process caused the soluble iron and copper to come out of solution so that they could be removed on filter bags.
After operating the Strengite Process on the system water, the chilled water system had final iron levels of 0.8 ppm total iron and < 0.2 ppm soluble iron. Copper levels were < 0.2 ppm (the limit of detection). No water was lost during the cleaning. The system remained in operation throughout the cleaning. The use of the Strengite Process for cleaning up the chilled water system avoided consuming and polluting approximately 20,000 litres of water.
The Strengite Process does not impact closed loop corrosion inhibitors such as nitrite and molybdate. The system water at Heckfield had a molybdate level of 20 ppm at the start of the process. It was unchanged at 20 ppm at the end of the cleaning.
The Strengite Process offers a more sustainable way to remove excessive iron and copper from closed loop systems.
Soluble metals become insoluble and are removed on filter bags.
The Strengite Process is a patented process. The technology, equipment and products for the Strengite Process are only available to licenced and trained water treatment specialists who operate to a high standard and skill level.
Strengite equipment used to clean the system.