Presentation on theme: "Power Washing and Overcoating is Effective and Much Less Expensive than Sandblasting and Completely Repainting a Bridge by Wayne Senick, Technical Director."— Presentation transcript:
1 Power Washing and Overcoating is Effective and Much Less Expensive than Sandblasting and Completely Repainting a BridgebyWayne Senick, Technical DirectorandCraig Ballinger, P.E.Termarust TechnologiesAbrasive BlastedHigh Pressure Water Cleaned
2 Advantages of Abrasive Blasting and High Pressure Water Cleaning Removal Of Lead based paintPrepare surface for zinc based coatingCosmeticsHPWCEffectively cleans structure critical crevice corroded connectionsCost effectively removes Non Visible contaminantsProvides a stable substrate for over coatingPotential for at least 50% project cost savings
3 1 yr old 3 coat zinc epoxy urethane over pack rust These Crevice corroded connections were not washed before coating to remove the active salts, not chemically treated to neutralize the active corrosion causing chemistries and were then sealed - which created an oxygen concentration cell and failure occurred1 yr old 3 coat zinc epoxy urethane over pack rust
4 Crevice Corroded Connection Washed before Abrasive Blasting and Coating to remove the active saltschemically treated with HR CSA penetrant to neutralize the active corrosion causing chemistriessealed up with a top coat based on HR CSA* neutralization chemistryCoating failure has not occur in 18 years*HR CSA (High Ratio Co-Polymerized Calcium Sulfonate)Crevice Corroded connections treated with an HR CSA* corrosion control coating on the High Level Bridge Edmonton, Alberta, Canada after 18 years the crevice corrosion has been stopped
5 Pack rust and Crevice corrosion can overstress structural connections
6 This structure has coating failure in the joints and connections, caused by severe crevice corrosion and pack rust, but the coating on the flat surfaces is relatively intact
7 Grit recycling unit and air mover with bag house Typical Recycling Equipment and Negative Air Containment used in Abrasive Blasting and Lead Removal OperationsGrit recycling unit and air mover with bag houseTwo complete negative air grit recycling systems with air compressors hooked in a train to be towed down the bridge as the containment movedTwo example of negative air containments
8 Water Collection, Containment and Surface Preparation Equipment for HPWC Lead Removal Project Shrink wrapped water tight ultra-light water collection containment7000 PSI 6 Gallon per minute hot Water HPWC Unit with salt remover injectorMovable flow thru tap system to contain paint chips and liquid waterPSI HPWC Units and Injector for Soluble Salt Remover
9 Complete Water Recycling and Filtration System on 100,000 square foot Bridge Project Pressure pumps to supply head pressure of 15 PSI for wash pumpsFresh and filtered water storageSettling Tank, Skimmer and Feed Pumps for Filter SystemWater passes thru 5 and 1 micron particle filters before going to storage for re use
10 Typical High Pressure Water Cleaning Surface Preparation Sequence with Adhesion Testing and Testing for Non–Visible ContaminantsHigh Pressure Water Cleaning using 5000 PSI, zero degree rotating tip, a 4 inch stand off distanceRemoval of black oxides by hand or power tool cleaningAdhesion Testing using a Hydraulic Pull-off tester, 300 PSI minimum for over coating, 300 hundred tests per 100,000 sq ft. Photo courtesy Ministry Transport OntarioTesting for Non Visible Contaminants before coating application
11 Where are the costsRemoval of lead based coatings by abrasive blasting and ultra high pressure water jetting micronizes the lead dust which makes it breathable and absorbable by plants.The containment for abrasive blasting is heavier and more expensive to construct because of the weight of the abrasive and the need for negative air pressure to facilitate environmental protectionThe surface needs to be washed to mitigate salts and the water must be collected. The washing step must be done, the water must be removed, and containment dried before blasting can take placeThe equipment required to contain, abrasive blast, collect and recycle the abrasive is much more expensive to buy and operate than a high pressure water cleaning system.
12 Adhesion of Remaining Substrate If stressed by HPWC (High Pressure Water Cleaning) at a minimum 5000 PSI with a zero degree rotating tip at a maximum 4 inch stand off distance specified, adhesion testing in the field has shown that this surface preparation method consistently will produce adhesion values over 300 PSI for the remaining coating.The owner should specify a minimum adhesion value no less than 300 PSI and adhesion testing must be done before coating is applied.The number of adhesion tests should be written into the specification. For example: a minimum of 300 tests per 100,000 square feet or whatever the engineer deems necessary based on the condition of the existing prepared substrateField experience has shown a hydraulic pull off tester meeting ASTM D4541delivered the most consistent results
13 Test Site Photos and Adhesion Test Log Sheets Site 24, Photo IM000824, 825 PSISite 33, Photo IM00833, 450 PSI
14 Test Site Photos and Adhesion Test Log Sheets Site 163, Photo IM001000, 720 PSISite 179, Photo IM001022, 340 PSI
15 Cost Savings Case Histories Rail Bridge 260,000 square feet Total removal of lead based coating systemNegative air containmentCollection, recycling or disposal of abrasiveStandard 3 coat zinc epoxy urethane coatingBid price 7.6 millionNo warranty providedHigh pressure water cleaning and over coatingCollecting the lead paint and recycling the waterHigh performance single coat HR CSA coating systemBid price $4.3 million5 year warranty including crevice corroded joints and connectionsCost Saving including a 5 year warranty = $3.3 million
16 Contractors Actual Cost Savings Analysis as Proposed to Owner Abrasive Blasting - 3 Coat Zinc System vs High Pressure Water Cleaning - HR CSA Coating SystemSpecifiedAir and dust impenetrable enclosureAlternativeFlow through tarps will trap paint chips and liquid water Cost savingMechanical ventilation system to protect workers sufficient to achieve a negative air environment within the enclosureNot required – no lead dust generated Cost savingExhaust ventilation system to provide filtration of the exhaust airWeekly instrument testing to verify airflow and negative pressure inside containmentNot required – no pressurized containment Cost savingAir lock entry wallNot required – no lead dust to contain Cost saving
17 Cost Savings “Continued” SpecifiedCleaning and securing of containment at the end of workdayAlternativeNot required – no lead dust to blow around Cost savingDaily assessment of visual emissionsNot required - no lead dust generated Cost savingFull time or part time high volume ambient air monitoringNot required – no lead dust generated Cost savingPackaging, storage, transportation, and disposal of waste generated by the projectReduction of generated solid waste, approximately 1300 tons.in addition, no waste solvent, paint cans or catalyzed paint to dispose of Cost saving
18 Cost Savings “Continued” Specified – coating systemStripe coat zinc1st layer zinc2nd layer epoxy3rd layer k urethaneAlternativePenetration for joints and connectionsCaulk coat + spot primePlus 1 layer wet on wet, instead of threeSeparate coats with curing time Cost savingSpecifiedCaulkingSealing of joints included in coating operation Cost savingSpecified – surface preparationSSPC-SP10 near white blasting andSSPC-SP7 brush-off blastingNot required Cost savingMeasure the surface profile of blast cleaned surfacesNot required – coating not profile sensitive Cost saving
19 Cost Savings “Continued” SpecifiedSpecified time restriction between cleaning and paintingAlternativeNot required – flash rust not an issue Cost savingContainment during coating applicationContainment not required for purpose of environmental protection or for a safe working environment.As coating is not hazardous, will contain overspray with flow through tarps. Cost savingSpecified – recoat timeApply each coat after previous coat has been allowed to dryAll successive coats can be applied wet on wet Cost savingSpecified – caulkingCaulking shall be applied to crevices not sealed, after the application of the second intermediate layer.Manufacturer’s note – Caulking must be allowed to cure for 5 – 8 days at 23ºC and 50% R.H.Caulk not required Cost savingWarranty 2 years or 5 years – separate price5 year warranty included Cost saving
21 Time Value of Money Example of one Owner’s use of the cost savings from HPWC are as follows:Cost saving will be invested during the 5 year warranty period ( shown on chart )On going maintenance program will be funded with earned interestAfter the 5 year warranty period the saved capital can now be used to fund another project
22 Case History Highway Bridge 100,000 square feet Total removal of lead based systemNegative air containmentCollection, recycling or disposal of abrasiveStandard 3 coat zinc epoxy urethane coatingBid price 3.5 millionNo coating system performance warranty availableHigh pressure water cleaning and over coatingCollecting the lead and recycling the waterHigh performance single coat HR CSA coating systemBid price 1.2 million5 year warranty including crevice corroded joints and connectionsCost Saving including a 5 year warranty 2.3 million dollars
23 Example Specification Surface Preparation SURFACE PREPARATION AND CLEANING:High Pressure Water Cleaning - The structure (or the portions of it to be coated) are to be cleaned using a 7,000 psi 6 Gal/Min hot water HP WC (high-pressure water cleaning)– with a zero degree rotating tip (at a maximum of a 4” standoff distance) to a (SSPC –SP12 WJ4- NV2 ) to remove loose paint and loose rust (SSPC SP2 &SP3 hand or power tool cleaning maybe used in inaccessible areas or when water cleaning is not possible). In some cases after HP WC there are areas of tightly adhered black oxide which was not removed. This tightly adhered black oxide even though it meets the WJ4 standard (and the active corrosion under it) is highly contaminated with Chloride &/or Sulfates &/or Nitrates and if allowed to remain, will result in delamination of the black oxide substrate and the coating which has adhered to it and must be removed.Crevice Corroded Joints and ConnectionsWhen using a 7,000 psi 6 Gal/Min hot water HPWC (high-pressure water cleaning) with a zero degree rotating tip (at a maximum of a “4” standoff distance) to a (SSPC –SP12 WJ4- NV2) The jet must be focused right on the crevice corroded joints and connections to flush them thoroughly. In addition to properly clean the joints and connections a soluble salt remover must be incorporated into the wash water. A minimum 100:1 solution of Chlor*Rid (manufactured by CHLOR*RID International (USA) or (CDN) or equivalent is required to remove as much salt from the joint as possible. This is mandatory when preparing crevice corroded joints and connections for treatment with the HR CSA Penetrant/Sealer and HR CSA Primer/Topcoat System.NV (Non Visible Contaminants) When it is expected (and/or confirmed by testing) that the surface of the steel is contaminated with soluble salts (Chlorides &/or Sulfates &/or Nitrates) – the HP WC (high pressure water cleaning) should be finished with or incorporated into the wash water initially a 100:1 solution of Chlor*Rid (manufactured by CHLOR*RID International (USA) or (CDN) or equivalent to remove those salts. (Just washing with water is not adequate because the salts are chemically & polar attracted to steel) [For additional information on this topic please access chlor-rid’s website]DRYING: It is required that even if the joints and connections look dry - that they be blown dry withclean, DRY, oil free, high pressure ( 100 psi) compressed air.
24 Example Specification Key Points Testing to determine whether or not wash water is hazardousIf water is hazardous - establish a collection and recycling or disposal systemCollection of any hazardous material including paint chipsDo adhesion test to verify surface preparation has been done correctlyDo testing to determine non visible contaminants have been removed to acceptable levels
25 ConclusionHigh Pressure Water Cleaning and a HR CSA coating system is a cost effective alternative to Abrasive Blasting especially on structures with structure critical crevice corroded and pack rusted joints and connectionsIn most cases washing is now specified for all painting projects for removal of non-visible contaminantsThe condition of the existing coating is not an issue as the HPWC surface preparation will remove any coating not suitable for over coating as proven by adhesion testing done in the fieldThe cost saving can be used to fund other projects or invested to fund the long term maintenance of the structure especially for private owners and toll authorities.
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