Assuring Good Results with Plural-Component Spray023-30)BasicTraining_4-15.pdfost plural-component...

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BasicTraining

Most plural-component spray op-erators are familiar with using and maintaining positive dis-placement pumps. A positive

displacement, or fixed ratio pump, traps a fixed amount of fluid inside the pump body and discharges it down a high-pressure paint hose. This is a reciprocating style of positive displacement and is used in the ma-jority of two-component (2K) airless spray equipment. Electronic variable ratio (EVR) pumps are a more advanced technology but they require more operational and maintenance knowledge. This article will provide informa-tion about eliminating some potential prob-lems when using EVR pumps.

Assuring Good Results with Plural-Component Spray

Building a Better MousetrapIn an effort to promote what some original equipment manufacturers view as industry progress and 21st-century thinking, spray equipment manufacturers have enlisted the services of their engineering departments to come up with new ways of designing protective coating application equipment. These ideas include, but are not limited to, more precise analytics such as measuring the gallons per minute (GPMs) dispensed, temperature deviations and pressure imbal-ances. For the contracting companies that employ personnel with an understanding of electronic dosing and metering these ideas certainly have a home within the industry. One might go as far as to say that in the

By Caleb Meacham, Solutions Consultant-WIWA LP

Workers applying plural-component spray coating to pipe exterior.Photos courtesy of WIWA LP

24 JPCL April 2015 / paintsquare.com

future, the directors and general managers who are responsible for hiring personnel into their organizations may use this as a measuring stick to decide who is consid-ered for a position and who isn’t. But at this point in time, suffice it to say that these applicators are, respectfully, few and far between. What the original equipment manufactur-ers fail to realize however, is that applica-tors have one primary goal: to transfer the coating from its storage container into the spray system and then onto the surface,

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Plural-component shop application.

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as quickly and as efficiently as possible. When an applicator has spent weeks, and in some cases months, familiarizing him or herself with the equipment that they have at their disposal and are then introduced to a different unit that calculates every aspect of the application right down to the hose sizes, it can be very intimidating and the results counterproductive. There may come a time when the majority of protective coating applicators who apply coatings with plural-component spray, will be using more of the EVR-style equipment that relies on dosing and meter-ing assemblies to determine and maintain mix ratios, but we are not there yet.

Out There in the FieldHaving been a field service technician myself, I understand the frustration that can come from premature equipment failure and lost production. Negligence on the part of the pump operator can not only cause a slowdown in production but can also cost the owner of the equipment a lot of money to repair. Regardless of the system being used, there are several tech-niques that can, and should, be implement-ed to ensure that the equipment continues to perform at its maximum capability. The first is that applicators must direct attention to the conditioning (bringing to

the appropriate temperature) of the coating before it’s transferred to the mix manifold, whether it’s mixed locally at the pump or remotely at the end of a hose bundle.

Hot & ColdRegardless of pump type, when material is introduced into the fluid section that has

not been heated to the optimal tempera-ture (i.e., the temperature specified in the product data sheet) pumps will be working much harder to move the material out to the mix manifold and the operator will need to turn up the pressure at the air mainte-nance unit in order to get the two com-ponents to atomize properly at the spray

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Coating applied to secondary containment and run-off.


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gun. This practice can cause excessive wear on the packings which will ultimately cause them to wear out faster, requiring replacement. On a fixed ratio system, improperly heat-ed material can put the main fluid pumps at risk of cavitation and premature packing degradation. Improperly heated material will hinder the dosing/metering valve’s ability to perform correctly. With an electronic variable ratio (EVR) system, improperly heated material will hinder the dosing/metering valve’s ability to perform correctly. Heat becomes a ma-jor factor in this situation due to the much smaller fluid passages inside the dosing/metering valve housing. If cold material is forced into these chambers not only will the integrity of the coating come into question but if the system is functioning correctly it will continuously shut down to prevent an off-ratio mix, costing the owner time, production, and in many cases, the added wear can result in preventable repair costs. Whether the system is being fed by transfer pumps pulling material of out 55- gallon drums or by feed hoppers mounted on the cart of the unit, proper conditioning is paramount and must never be rushed. In the same vein, additional heating components such as drum band heaters, heat blankets and hose bundle heat can be just as important if high levels of production are to be achieved. Most plural-component systems come equipped with inline paint heaters to assist in bring-ing temperatures up at the pump before the operator throws the switch into spray mode.

These heaters are a must when applying any 100%-solids material. If an applicator is running a hose bundle from the pump to a remote mix manifold, simply insulating the hoses without running either hot-water-jacketed hoses or an electrical heat trace ribbon inside the bundle will be detrimental to successful application. The

temperature decrease that takes place when the material travels from the pump to the mix manifold, especially when the hoses are resting on a cold concrete floor, can add up to 10 degrees, not to mention temperature loss due to ambient condi-tions and the temperature of the material in the supply containers. To combat this

Protective coating being applied to control box panels.


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problem, the applicator can run recircula-tion lines from the mix manifold back to the pump which will create a closed loop. The material travels in a circular pattern and will maintain its temperature all the way out to the spray gun. This is not only important in cold weather climates but also when the equipment is used outdoors if the

temperature is below 70 F . When cold material introduced into the spray system is not given ample time to heat up (particularly when it’s mixing with material already in the process of being warmed), it will shock the system, creating cold patches in the pumps and hoses and will potentially throw the system off

ratio. This is especially dangerous if the applicator is in the middle of a project. The material must be thoroughly heated in the storage container (drum or hopper). If the operator knows that he is going to empty a drum before finishing the project, another drum should be heated and agitat-ed before the first drum empties so that once the feed pump has been repositioned into the new drum, the transition will be as seamless as possible. If the feed system used is a hopper and the levels inside are permitted to drop to the bottom, any new material that is loaded which has not been preheated, will force the applicator to bump up the spray pressures and create more wear and tear on the fluid sections. The type of production is inconsequential. If the heat is insufficient, it can create sev-eral problems. Regardless of whether the system is an EVR or a traditional positive displacement unit, heat is the operator’s best friend. The evolution of EVR-style application systems has been both unique and discon-certing in that while the technology offers much more in the way of data logging and analytics, it can also invite reluctance from potential owners and operators. Measuring and displaying gallons dispensed, average spray pressures, material temperatures and error messages can be useful, but the operator must be trained in collecting the data and sharing it with colleagues. The idea that all of this information can be logged and filed away is a tremendous resource for those looking to calculate exact amounts of material applied and work stoppages but the fact of the matter is that many applicators in the field are still shying away from this technology either because they aren’t ready for it or because they simply don’t need it and do not wish to pay the added expense to obtain it. Those who are using it or have experiment-ed with it have reported concerns to man-ufacturers of this equipment, asking for



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more user-friendly systems. This is not limited to traditional epoxy and urethane applications but has crossed over into the application of intumescent fireproofing products as well.

ConclusionAgain, the goal of the applicator is to transfer the material from the storage container onto the substrate in as little time as possible, performing a quality job with as few hiccups as possible. As stated above, there may come a time when EVR spray systems are commonplace in the field, but because of the inconsistencies with dosing and metering along with over-engineering, there is a good chance that we will continue to see more in the way of fixed ratio systems that only ask the operator to feed air to the system and regu-late its pressure manually without any electronic interference. It’s been said that there is a time and place for everything under the sun, but old fashion simplicity is the most valuable commodity in this industry, especially regarding high produc-tion plural-component spray equipment and each OEM with a product or service to offer should be prepared to align themselves with what their customer desires, not the other way around.

About the AuthorCaleb Meacham has been involved in the designation, sale and repair of airless spray equipment including plural-component systems, since 2005. He has directed operations in spray departments and overseen maintenance schedules in repair fa-cilities before coming to his current

position as a Solutions Consultant for WIWA LP. He lives in Dallas, Texas.

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