Introduction & Overview of Plural Component Spray Technology

Introduction & Overview of Plural Component Spray Technology
Applying Plural Component Spray Presented By: Art Webb, Naval Research Laboratory Copyright 2010, Version 2

Learning Outcomes At the end of this webinar the student will be able to: Recognize the use of plural component application Define a high solids coating Identify plural component application systems available Recognize the methods for properly mixing material or coating components (e.g., Part A, Part B) Copyright 2010, Version 2

Why the Interest in Plural Component Application
Introduction & Overview of Plural Component Spray Technology Why the Interest in Plural Component Application Economics Environmental Compliance Application Readiness Safety Application Quality Economics Customers want coating systems to last longer in order to reduce maintenance cycles and maintenance costs. Customers want a coating system currently lasting 5-10 years to now last 12, 15, 20 years. Environmental Compliance Customers want to apply more environmentally friendlier coatings (lower VOCs, lower HAPs) to comply with regulations and reduce solvent waste. Application Readiness Customers want faster turnaround on coating jobs to get applications back in service more quickly- PC application allows for quicker film build in fewer passes and faster curing. Safety High solids applications use less or no solvent during application- reducing explosion risk in confined spaces such as tanks, wastewater manholes and other interior void areas. Application Quality Higher film builds, low sagging properties, better barrier protection, better corrosion protection Edge retention properties for better edge protection CAUTIONARY NOTE: Too high a film build can cause problems with adhesion (getting the coating to stick to the surface) due to poor wetting properties. Also, edges must be properly prepared (e.g., rounding corners, eliminating sharp edges according to specification requirements) for best coating performance. Copyright 2010, Version 2

High-Solids Coatings For our purposes, high-solids coatings are considered to be at least 90% solids Even though coatings are solvent- free, they are only about 98% solids when analyzed by heating. For the purposes of this webinar, high solids coatings will be considered to be solvent- free. Copyright 2010, Version 2

Various Names for A and B Components A Component B Component Base Catalyst Resin Amines Prepolymer Isocyanate Polyol Accelerator or Promoter Activator Designation of Components of Two- Package Coating Systems Component A is typically called the base, resin, or binder component Component B is typically called the co- reactant or curing agent Copyright 2010, Version 2

Plural Component Coatings
Characteristics of Plural Component Coatings Plural Component Coatings Types e.g., Epoxies / Polyurethanes / Polyureas Components of a Typical Epoxy Component (A): Resin or Base Component (B): Co-reactant or Curing Agent Curing Mechanism Reaction of Components A and B to form a chemically crosslinked protective film Coating Types Epoxies are the workhorse anticorrosion coatings for the general industry and the U.S. Navy. There are many variations (formulations) available based on service, environment, and length of time protection is needed. Aliphatic polyurethanes offer UV protection and flexible dry film characteristics. Curing Mechanism Although chemical crosslinking is the principle method of achieving the cured film, epoxies also experience a drying or solvent evaporation phase. If the solvents are not effectively evaporated from the film they will interfere with the chemical crosslinking process. Poor ventilation, excessive film build and applying a second coat too soon can cause incomplete removal of solvents. Curing is time and temperature dependent and may require additional time to achieve full cure to be placed into service. Copyright 2010, Version 2

Characteristics of Two Component Epoxies
Characteristics of Plural Component Coatings Characteristics of Two Component Epoxies Ratio Volume by ratio of Components A to B (i.e.. 1:1, 4:1) Induction Time (Sweat-in-Time) Time mixed components must stand to allow for initial chemical reaction prior to application Pot Life Time mixed components remain usable without affecting applied coating performance Ratio The ratio of a given product is critical to its formulated performance. Variations due to partial kitting or incomplete mixing will affect the intended properties of the applied coating. Check with the manufacturer for % off-ratios due to use of partial kits or incomplete mixing. Compare to plural component equipment degree of accuracy. Always verify that you are mixing the correct components. Never exceed off-ratio variances allowed by the manufacturer and the customer. Induction Time Not all products require induction time. Induction time is typically influenced by material temperature. The higher the temperature the shorter the induction time. When using plural component spray equipment check with the coating manufacturer for product suitability during pre-heating and static mixing. Pot Life Pot life shortens as material temperature increases. It is defined in terms of time, both in the container, as well as the spray hose. Always check with the manufacturer for induction time and pot life. Copyright 2010, Version 2

Characteristics of High Solids Epoxies
Characteristics of Plural Component Coatings Characteristics of High Solids Epoxies Solids by Volume Primer Characteristics Topcoat Characteristics Solids by Volume- referred to as 100% solids, typically 98% +/- 2% Primer Characteristics- formulated to provide good surface wetting characteristics Topcoat Characteristics- Formulated to provide high-build edge retention capability Copyright 2010, Version 2

Characteristics of High-Solids Epoxies
Characteristics of Plural Component Coatings Characteristics of High-Solids Epoxies Viscosity (resistance to flow) Generally twice that of solvent based epoxies Higher pressure required to pump and atomize Heating coating reduces viscosity Pot Life Measured in minutes vs. hours (ex °F) Exothermic reaction (heat generated by mixed components in container) Viscosity Higher viscosity and lack of solvent as a natural lubricant causes excessive drag on the higher solids epoxies as they move through a spray system. Material temperature at time of application is critical. Lower viscosities are achieved with warmer material temperatures. The extent of pre-heating will be governed by method of application. Pot Life Traditional solvent based epoxies may have a pot life of 4-6 hours at 77ºF Excessive pre-heating of components when “hotpotting” will increase the exothermic reaction and shorten the pot life. The larger the container of mixed material, the greater the exothermic reaction. Heated plural component systems reduce viscosity with minimal risk of exceeding pot life. Copyright 2010, Version 2

Characteristics of Polyurethane Coatings
Characteristics of Plural Component Coatings Characteristics of Polyurethane Coatings Polyurethane Coatings Advantages Limitations There are many types of polyurethane coatings used for plural component applications. Polyurethanes can be formulated for both protective and decorative purposes and can offer thin films, semi-rigid films, thick films, and flexible elastomers. Generally, polyurethanes exhibit excellent UV and color-retentive properties. Advantages of Urethane Coatings Color/ Gloss Retention Adhesion Acid/ Alkali Resistance Impact/ Abrasion Resistant Limitations of Urethane Coatings Cost Multi- Component Limited Pot life Moisture Sensitive During Cure Short Recoat Intervals Heat Resistance to 177ºC Contain Isocyanates Copyright 2010, Version 2

Characteristics of Moisture-Cured Urethane Coatings
Characteristics of Plural Component Coatings Characteristics of Moisture-Cured Urethane Coatings Moisture-Cured Urethane (MCU) Coatings Advantages Limitations Advantages of MCU Coatings Single Component Surface Tolerant Ease of Application- Depending on NCO Content Low Temperature Cure Tolerant of Dew on the Surface Chemical and Solvent Resistant Gloss Retention Limitation of MCU Coatings Package Stability May Out-Gas Copyright 2010, Version 2

Polyurethane Advantages
Characteristics of Plural Component Coatings Polyurethane Advantages Turn Around Time 100% Solid Ability to Apply During Winter Months Unique “Self-Inspecting” Property The advantages of polyurethane coatings are: Polyurethane coatings can be made to cure at virtually any given time by changing the amount of catalyst or the type of polyol in the formulation. Thus, fast-setting, one coat polyurethanes have a much faster turn around time than most coatings. One hundred percent polyurethane coatings are solvent free and have low toxicity levels. Due to the exothermic nature of the reaction between polyol and isocyanate, polyurethane coatings can cure at almost any ambient temperature. This means that polyurethane coatings can be applied even during the cold months of the year. One hundred percent polyurethane coatings feature a unique “self-inspecting” property; they fail almost immediately if they are incorrectly applied or if there is a problem with the surface preparation or the mixing ratio. Thus, polyurethane coatings can be inspected immediately after application and any defects in the coating will be visible. Copyright 2010, Version 2

Plural Component Application Process - Summary
Components A and B are power mixed/agitated separately Components are heated to reduce their viscosities and re-circulated uncombined from the reservoir to the mixer and back until the desired temperatures and viscosities have been reached and maintained Both components are pumped separately in their desired proportions (flow rates) toward the spray gun Components are combined in a manifold/mixer immediately before reaching the gun Copyright 2010, Version 2

Examples of Plural Component Spray Units
Above are examples of plural component spray units: Frame mounted unit Portable unit Mobile trailer unit. A B C Copyright 2010, Version 2

Heated Hose to Manifold
Plural Component Equipment Schematic Heater B Gun 1 “B” Heated Hose to Manifold 55 gal. “B” Supply Agitator and Elevator Mix Proportioner “A” To Catalyst (B) Inlet Gun 2 The above schematic shows the plural component system components. Heater A “A” Inlet “B” Inlet 30:1 Solvent Flush to Mix Manifold 55 gal. “A” Supply Agitator and Elevator To Resin (A) Inlet Copyright 2010, Version 2

System Components Feed system Pump/proportioning system Hoses
Heating system Mixing manifold system Spray gun Copyright 2010, Version 2

Feed System Feed Systems
Causes each component to flow to the inlet of its mechanical proportioning or metering pump May be a gravity or pressure feed system Front- end filter used to remove coarse particles that might clog tip Supply or feed system pressure should not exceed 25% of spraying pressure* * NOTE: If this percentage is exceeded then there is a possibility that the feed system will overpower the intake balls and check valves in the proportioner pump thus causing an incorrect mixing ratio. Pressure feed systems are most common Copyright 2010, Version 2

Feed Pumps Pressure Feed Systems
Pressurized containers or pumps push each component to the inlet of the proportioning pump Most commonly used, although more costly Less likely to introduce air into the system- air trapped in the system can cause major problems resulting in an incorrect mixing ratio or excess wear on pump The purpose of the feed system is to pump the material to the inlets of the proportioning pumps. This eliminates the possibility of air pockets in the system Proper priming is essential for the correct operation of all pumps and proportioner. Air trapped in the system can cause an incorrect mixing ratio and cavitations (pitting or damage) that will accelerate pump wear Copyright 2010, Version 2

Characteristics of Pump Systems
Available Spray Pressure Normal atomization/spray pressure Flow rate Compatibility of wetted parts with materials pumped Power source The available spray pressure is dependent on the plural component equipment. Normal atomization/ spray pressure used during application is between 2,500-5,000 psi. The recommended flow rate is dependant on the tip size and fluid pressure. The power source can be either air or electric. Copyright 2010, Version 2

Characteristics of Pump Systems - Impact on System
Feed pumps must be of a sufficient size Need sufficient spray pressure Feed pumps must be of a sufficient size to supply the proportioner when operated at its maximum volume output. In order to apply a coating properly, sufficient spray pressure is needed. The best pressure to spray at is the lowest possible pressure to get the job done. Copyright 2010, Version 2

Power Sources for Pumps
Air-powered supply pumps Hydraulic supply pumps Air-powered supply pump benefits: Readily available power source Easy to install Hydraulic supply pump benefits: More efficient than air- powered pumps Quieter operation Note: Air is the most common source of power for industrial/marine protective coatings Copyright 2010, Version 2

Photo of Proportioning (Metering) Pumps
Proportioning Capabilities The pump is the part of the equipment that moves the paint through the system. Pumps may be fixed, variable, adjustable ratio Pumps have ability to maintain volumetric ratio Pumps ratios (by volume) are most commonly 1:1 and 4:1 Filters constitute an essential element Fixed ratio is when the pump equipment is set to allow for a pre- set ratio. Some manufacturers make replacement parts so pumps can be modified for different ratios Check with your equipment manufacturer for the capabilities of the pump you use Courtesy of WIWA Courtesy of Graco, Inc. Copyright 2010, Version 2

Critical Nature of Mixing Ratio
Proper Ratio Check Ratio Off-Ratio Monitoring System The proper ratio is needed for proper curing. A plural component system ratio must always be checked before beginning work and after stoppages, as required. The mixing ratio should be within the manufacturers specified range A monitoring system is used to maintain the proper mixing ratio, as well as temperatures and pressures It is the responsibility of both tender and applicator to ensure the ratios are correct during spraying operations Copyright 2010, Version 2

Unit Control Panel Digital Heat Controls Digital Pressure Control
Cycle Counter PSI or Bar F° or C° Park “A” pump Target and Actual Temp Error Codes Stop Remote Mountable Controls - Up to 30.5 m As the plural component pump operator it is critical that you understand the codes and numbers on the unit you operate to avoid major problems. Some units manufactured outside of the USA will likely have gauges and control panels that use Celsius temperature numbers (Cº) instead of Fahrenheit numbers (Fº), or Bar instead of PSI Copyright 2010, Version 2

Heated/ Insulated Hoses
Heated hoses can be used to maintain heat but not to build heat, therefore the heating system must bring material to operating temperature before spraying. Job site conditions and requirements will dictate where to use insulated and heated hoses such as weather, distance from unit to work area, ambient temperature, and application time. Note: Using a hose that has too small a diameter will produce too much internal friction and may cause pressure drop at the pump Copyright 2010, Version 2

Portable Unit with Spray Hose
For mixed side, hose lengths should be relatively short (General industrial/marine applications recommends a maximum of 200 feet) A short whip hose of adequate diameter may be used to provide applicator flexibility Hose diameter varies with product applied, typically 3/8-1/2 inch for high viscosity coatings Color coded hoses are recommended for each different product sprayed to minimize problems/confusion at the work site Copyright 2010, Version 2

Heating System (In-line)
Drum and in-line heaters at the pump are used to heat the components to desired temperatures for application (consult manufacturers product data sheets or technical representative for recommendation) Each component is recirculated through an insulated hose from the pump to the manifold, usually with in-line heaters to maintain the elevated temperature It is necessary to stabilize the temperatures of the components before mixing them together to avoid an incorrect mixing ratio or inadequate mixing The heaters that are commonly used for epoxy coatings are explosion proof, high-mass heaters. These heaters are explosion proof because of their use with solvent based coatings. High-mass refers to the style of heating. The heating element heats up the metal core of the heater. The core has the fluid path wound around the core and the heat is transferred from the core to the paint as the material travels through the heater. Copyright 2010, Version 2

Coating Material Temperature Requirements
Too low a temperature will restrict flow Too low a temperature may also cause amine blush or amine bloom as it is sometimes called It is important to: Bring material up to the manufacturer’s recommended temperature prior to application Maintain proper temperature during application- monitor routinely every 5-10 minutes by recording temperature reading from the control panel located on the plural component equipment or by infrared gun Check temperature when adding new cold material to warm material already in the system Factor in adding “cold” material to the system and waiting for temperature of material to come up to required levels when planning a job Mix additional component A or B to the required temperature before adding to prevent an incorrect mixing ratio Copyright 2010, Version 2

Amine Blush on Steel Amine blush (formation of a milky substance on wet surface of amine- cured epoxies caused by reaction with carbon dioxide in the air and water in the air) must be removed before applying topcoat Copyright 2010, Version 2

Taking Material Temperature Using Infrared Gun
It is important to verify the temperature of the material for proper consistency and application every 5-10 minutes. One method to measure the temperature of the material is by using an infrared gun. Copyright 2010, Version 2

Critical Material Temperature Check Points
Storage Temperature Reservoir/supply container Pump Manifold Gun The following are critical check points for the material temperature: Storage temperature Reservoir/supply container Pump Manifold gun Copyright 2010, Version 2

Mixing Manifold System
The mix manifold is where the material components A & B are brought together to be mixed at proper ratio. Mixing Manifold System Can be mounted on the proportioning equipment or located remotely Joined to hoses (with shut- off valves) containing components A and B and purging/ clean- up solvent The static mixer uses baffles or injection to thoroughly mix components May be joined to two or more spray hoses Mixing manifold maintenance and care Copyright 2010, Version 2

Manifold Mixer Pre-heating, Proportioning, and Mixing Before Transfer to Gun Piston proportioning pump used Mixed components are pumped from machine mixer to gun Coatings with short pot life must be applied immediately After interrupting application, residual mixed coating must be cleaned from gun and lines with solvent to prevent damaging them Copyright 2010, Version 2

Mix Manifold System Mix Manifold Mix Manifold Assembly and Connections
Mixing Manifold Maintenance & Care The material is brought up to the mix valves and held there until the mixing unit is switched to spray. Once the mix manifold is turned to spray the materials are introduced into the mix chamber and into the static mixer. This is the “point of no return.” That is, now you have mixed material in the mix block, the static mixer, and the spray line so the operator must maintain awareness of the pot life and flush when appropriate. Most facilities store these manifolds detached from the machines. This means that proper reconnection is critical so that all hoses are hooked into the correct port. If the hoses are mismatched then the component ratio will be incorrect. Monitoring systems will not pick up this type of problem. Note the mixing manifold should be carefully handled since they are more difficult and more costly to replace than hoses. Copyright 2010, Version 2

Mixing Block (isolated)
Introduction & Overview of Plural Component Spray Technology Mixing Block (isolated) Heated Components Mixed at Remote Mix Manifold Piston proportioning pump used Individual components (parts A and B) mixed at manifold and pumped to gun Distance from manifold to gun may limit acceptable pot life After interrupting application, residual coating must be cleaned from manifold, spray hose, and gun with solvent to avoid damaging them In most cases when a mixing block is used, you only have to solvent clean from the mix block (after where A & B are mixed) to the gun on a daily basis. However, some equipment manufacturers may recommend a complete solvent clean weekly or at the end of a job or if materials are changed out. Copyright 2010, Version 2

Solvent Purge System Used to flush mixed components from manifold, spray hose, and gun Solvent Purge System Used to flush mixed components from manifold, spray hose, and gun Purged material must be collected in pail or other container for proper disposal Hazardous waste, such as solvents, must be tested, treated and disposed per applicable regulations. Copyright 2010, Version 2

Purging of Mixed Components After Interruption of Work
Mixed components must be solvent purged or flushed from the gun whenever application is interrupted for several minutes Purging of Mixed Components After Interruption of Work Mixed components must be solvent purged or flushed from the gun whenever application is interrupted for several minutes Follow the manufacturer’s recommendations for interruption time and solvent purging Purging here refers to flushing or cleaning equipment components when mixed coatings are present Filter solvent to avoid cross-contamination of solvent used in part A and part B lines. It is important not to mix these solvents! If part A solvent mixes with part B solvent trace contaminants from the resin and hardener could cause a chemical reaction in the lines Copyright 2010, Version 2

Equipment Clean-up Plural-component application equipment must be thoroughly cleaned after use, especially interiors of pumps, manifold, hoses, guns and tips Equipment Clean- up Plural- component application equipment must be thoroughly cleaned after use, especially interiors of pumps, manifold, hoses, guns, and tips Follow the cleaning instructions of the equipment manufacturer Use the cleaning solvent recommended by the coating supplier CRITICAL ISSUE- Typically in the field, not enough time is allowed for cleaning equipment. Please emphasize this with your supervisor and general foreman. Cutting corners here can be costly later Copyright 2010, Version 2

Cut-away of plural component impingement gun with component hoses joined at the tip Heated Components Mixed at Gun Tip (Polyurethanes and Polyureas) Piston proportioning pump used Individual components mixed at gun tip (impingement) Harder to monitor mix ratio Pot life can be very short (e.g., a few seconds) After interrupting application, only gun tip must receive mechanical or air purging Note: This type of mixing equipment is typically used for spraying polyurethanes and polyurea materials. Copyright 2010, Version 2

Airless Spray Gun When Spraying of Components From Gun Make Sure You Have: Proper Atomization Proper Spray Pattern Coating Thickness Solvent Purging of Residual Mixed Components Clean Equipment Good Applicator Communication Established Coating Repair Method We will explain these in more detail in the following slides. Copyright 2010, Version 2

Proper Atomization Atomization occurs in airless spraying when coating is forced under high pressure through tip orifice Proper Atomization Two factors may affect atomization - Fluid Pressure - Material Viscosity Excess fluid pressure may cause more bounce- back (overspray) and increased tip wear and line wear Low fluid flow may cause formation of tails (fingers) at ends of fan Use lowest practical fluid pressure to reduce overspray and for work in tight areas Insufficient atomization may be caused by: debris, clogged filters, clogged tips, tip wear, etc. You can’t just keep cranking up the pressure to get proper atomization. It is the last resort. Troubleshoot other areas first before cranking up the pressure. Copyright 2010, Version 2

Factors Affecting Spray Pattern Size
Size of tip orifice (typically to 0.021) Wear of tip Fan angle Distance of gun from substrate being painted Distance of gun from the substrate being painted (usually about 12 inches) is critical. If you are too close you will get flooding. If you are too far dry spray is most likely. Smaller tips and smaller fan sizes may be required in confined spaces, painting small objects, or when striping by spraying. Copyright 2010, Version 2

Tip Wear High solids coatings wear tips more rapidly than traditional solvent borne coatings As Tip Wears Away: The spray pattern will be distorted The fan width will decrease to form a rounder pattern resulting in thicker coating film application The thicker wet coating film has a greater tendency to sag Time used or changes in spray pattern usually dictates tip replacement Note- Distorted spray patterns are usually called fingers or tails by painters Copyright 2010, Version 2

Diagram of Changes in Airless Spray Pattern with Tip Wear
Choose tip size applicable to the product and type of area being painted. Consult the product data sheet or coating material technical service representative for recommended temperature, pressure and tip sizes. Make sure manufacturer’s representative know aspects of the job at hand, so recommendations given to you make sense. Copyright 2010, Version 2

Application Thickness
Theoretically, wet film thickness of high-solids coatings is the same as the dry film thickness Area with restricted working space can easily become coated with excessive film builds Application thickness should be measured using a wet film to determine if it will meet requirements when the coating dries. Excess film build should be avoided. It is important to provide adequate ambient temperature and ventilation for curing. To avoid excessive film builds use smaller tips and guns when practical to reduce coating thickness and improve accessibility. Proper training of applicators can also improve coating application in tight areas. Copyright 2010, Version 2

Matching of System Components
All system components should be properly matched for size and capacity The heating system should also match the components Clean, lubricate and otherwise maintain equipment parts for best service Never modify equipment without consulting with manufacturer Matching of System Components All system components (pumps, hoses, manifold, filters, and spray gun components) should be properly matched for size and capacity as recommended by the manufacturer The heating system should also match the components and be operated in accordance with manufacturer’s instructions Clean, lubricate and otherwise maintain equipment parts for best service. When equipment is not in use, cover it to protect it from dust and other contaminants. Do planned maintenance and part replacement as recommended by the manufacturer regardless of whether parts require replacement at the maintenance schedule. This will greatly reduce undesired equipment breakdown during operations when production is key Never modify equipment (e.g., fittings and connections) without consulting with manufacturer. Use equipment only as intended Copyright 2010, Version 2

Plan the Work Application team should be briefed about planned work before beginning it. The application team should be briefed about planned work before beginning it. For example: How many painters will be required to do the job? How far from the equipment is the coating project? This will determine how much hose is needed. Has thought been given to how much pressure is needed at the spray gun and how to get that pressure out to the coating project? How will heat be maintained throughout the lines as the material is pushed several hundred feet to the work site? How much material and solvent will be needed? Copyright 2010, Version 2

Summary In this Unit, we covered: Why industrial/marine customers are considering use of plural component spray technology to apply 100% solids coatings Brief introduction to high solids material Plural component application systems Mixing methods Copyright 2010, Version 2

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Introduction & Overview of Plural Component Spray Technology

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