Getting the Most out of Airless Spray
如何最有效的使用无气喷涂机--未完待续防腐蚀论坛 @chris1986 原创翻译
paintapplication using airlesse quipmentis, and has been for many years, the methodof choice for large industrial painting projects. Although the industry is awareof the differences in the equipment from various suppliers, some of the basicsof airless application common to all equipment manufacturers are not being effectivelycommunicated to applicators. It is important to the quality and economics of theproject that everyone understands and pays attention to these basics.
无气喷涂机涂装在大型涂装工程领域已经应用多年，然而一些涂装操作中的常识却因制造商和施工者的沟通不良而被忽略。这些知识的了解对于项目中的所有成员至关重要。
Thereare four areas that demand better attention by applicators and paintmanufac-turers. These are:
1) Wornspray tips,
2)Excessive application pressure,
3)Proper tip selection, and
4)Variability in applied film thicknesses.
操作技巧关注以下四点：
1）喷嘴磨损
2）操作压力过大
3）合适喷嘴的选择
4）涂膜厚度的多样性
Anumber of factors, including tip selection, application pressure and appliedthickness variability can affect the quality of an airless spray applicationjob.
许多原因，其中包括喷嘴的选择，操作压力、涂层厚度变化等以上几点都会对无气喷涂质量产生影响。
WornSpray Tips
喷嘴磨损：
Nothingwill waste more paint in less time than a worn spray tip. Most specificationsrequire the painter to apply the coating to a minimum dry filmthickness (DFT). Worn tips increase the average DFT by affecting the
uniformityof the applied paint film. Worn tips also affect quality.
在短时间内没有什么比使用磨损的喷嘴涂装更浪费涂料了。大部分技术指标要求涂层达到最小干膜厚度（DFT：minmum dry film thickness：最小干膜厚度）。使用磨损的喷嘴会使涂装后漆膜的平均DFT升高，也会对质量产生影响。
Atip is completely worn out if the spray pattern is round. The easiest way tounder-stand the dynamics of a tip is to think of the round pattern being theresult of spraying the paint through a circular hole. A proper spray patternis elongated. This isachieved by squeezing the metal on two opposing sides ofthe circular opening. The more it is squeezed, the flatter the fan, hence the widerthe spray pattern.
若喷涂出的图像是圆形，那说明喷嘴已经完全磨损了，其可简单的理解为：涂料通过一个圆形孔洞喷射形成的圆形图案。一个正常喷涂后所应形成的图形是细长方形，这是涂料对金属片上的两个位置相对的圆孔施压所形成的，施压越大，扇形面越平，因此喷涂出的图形会越宽。
Inactuality, there are two little “wings” of metal that are used to “squeeze” thefan.The spray pattern becomes rounder and rounder as these pieces of metal areworn away by the abrasive action of the pigments in the paint. As the openingbecomes rounder, the paint is deposited on the sur-face too quickly to control,and the resultant application is usually unacceptable. However, long beforethe “wings” are com-pletely worn away, the tip or nozzle will stop depositing auniform amount of paint across the entire fan width. The amount ofpaint in the center of the fan increases. If the fan is not uniform, appliedDFT variability increas-es and more paint is needed to achieve the minimum DFT.
实际上，这有两个金属小“翅膀”用来“挤压”扇面。喷嘴中的金属件被涂料中的颜料所磨损，其磨损的越厉害，喷射出的图形会越圆。当喷嘴中的圆孔变得更圆时，涂料就会很快的堆积在表面而变的难以控制，此时涂层的判定结果就是不合格了。然而，早在“翅膀”着穿之前，喷嘴就会阻止沉积的油漆从整个宽度的扇面下统一流淌下来。此时处在扇面中心的油漆量更多了。假若扇形不是统一的，则表明操作的DFT多样性升高，此时若想达到最小DFT，需要使用更多的涂料.
Thephoto at left shows satisfactory drip from a new spray tip, while the photo atright shows a drip pat-
ternindicating that the spray tip is worn.
Courtesyof Gary Tinklenberg, Corrosion Control Consultants & Labs, Inc.
左边的照片为合格的新喷嘴中漆滴 的图形。 右边为已磨损的喷嘴所喷出漆滴的图形。--腐蚀控制协会、实验室提供。
Thereis a very simple test to determine if a spray tip is worn. Take a piece ofcard-board (or any smooth surface) and mount it in a vertical position. Holdingthe spray gun as steady as possible and in a position to create a horizontalpattern on the surface, apply a short burst of paint.Obviously this will result in an excessive amount of paint beingapplied, and the paint will drip or run down the surface. Examine the drippattern. If the drips are all uniform, evenly spaced and of equal length, thetip is satisfactory. If the drips are longer in the center of the pat-tern, thetip is worn and should be replaced.
这有一个很简单的试验来检查喷嘴是否磨损。拿一块纸板（或是任何表面平整的物体），将其垂直竖立。手持喷枪平稳的向纸板表面上喷一阵，显然此时过量的油漆会从纸板表面滴下或流淌。检查滴痕，若滴痕是统一、等间距且等长，则喷嘴为合格。若图形中心位置的滴痕长于其他位置的，则说明此喷嘴 已磨损该被更换了。
Thisvery simple test should be performed at least daily.Why is it that something soeasy and cost-effective is not part of many profes-sional painters’ routines?The answer is sim-ple. Sometimes the true cost of a job is for-gotten. Too muchimportance is placed on the cost of equipment rather than on the cost of paintand labor to apply it.
这个简单试验应至少每天操作一次。 这个方法如此简单且节省成本，为什么不能成为大多数油漆专家每天的例行工作？答案很简单：有时我们遗忘了工作成本，太多关于设备成本这类重要的事需要关注而往往忽视了涂料成本和工人操作规范。
First let’s consider the cost of paint. Once thesurface is blasted, it generally needs to be painted as quickly as possible.However,worn spray tips can easily result in an average applied DFT of 25microns (1 mil) greater than a coating film applied with new tips.
首先来考虑涂料成本。一旦表面喷砂完毕，通常要尽快的喷涂，然而，使用磨损的喷嘴会比新喷嘴喷出的平均DFT厚25微米/ml，
Thisproblem can result in the application of as much as an extra gallon (3.8liters) of paint to every 500–800 square feet (46–74square meters) of surfacearea, depending on the volume solids of the paint and the configuration of thesurface. The cost of wasting this much paint could certainly pay for a new tip.
此问题在施工中会对结果产生影响。根据油漆的固形物百分比和表面配置，这个问题会导致每喷涂500 - 800平方英尺(46 - 74平方米)的面积,要额外多用1加仑(3.8升)的油漆，被浪费的这些油漆的成本都可以用来买一个新的喷嘴了。
ExcessiveApplication Pressure
过大的操作压力
Mostapplicators are aware that low pres-sure in spray equipment can causeprob-lems, but they are not aware or do not believe that high pressures canalso cause problems. It is rare to see applicators adjusting spray pressures asa matter of routine, even when starting a new project with a new paint. But toomuch pressure can be costly and can affect quality.
大多数操作员都知道低压喷涂操作会导致问题,但他们并不知道或不相信高压也会导致问题。很少有见到操作员把每天调整喷涂压力当做例行工作来做。 即使在用一种新涂料开始一个新项目时，也没人调整过喷涂压力。但是使用过多的压力会使成本高昂且会影响质量。
Thetail pattern in this photo is a result of too little applicationpressure.--Courtesy of Gary Tinklenberg, Corrosion Control Consultants &Labs, Inc
图片中的类似尾部的图像是因操作压力过小造成的。--腐蚀控制咨询、实验室。
The proper pressure is affected by sever-al variables, includingtemperature, paint vis-cosity, batch-to-batch variability, hose length, andresistance to flow. Since it is impossible to know the consequences of allthese variables each time paint is applied, a simple field method is needed toarrive at the proper pressure. If there is insufficient pressure, the spraypattern will result in “tails” (Fig. 3). A “tail” pattern is evidence of an incompletefan. In other words, as the spray gun is moved through a normal stroke, thereis a line of paint at the top and bottom of the spray pattern that is separat-edfrom the rest of the pattern. If tails are present, the pressure must beincreased to the point where the tails disappear.
合适的压力会受诸多方面的影响，其中包括气温、涂料粘度、批次变化、管路长度、流体阻力。鉴于每次喷涂时不可能知道是哪些变量所造成的结果，所以需要一个简单的现场试验来判断压力是否合适。若气压不足，则喷出的图像参照图3。这个“尾部”图形是非完整扇形的一部分或者说是一个体现。也就是说，当喷枪沿着正常的移动路线喷涂时，在图像的顶部和底部会出现一条漆线且与图像的其他部分单独分离出来。若这个尾部图像出现，则喷涂压力一定要提高到直到尾部图像消失为止。
Againthe question must be asked: why is something so simple not a part of a typicalpainter’s daily routine? There are several rea-sons, but the most important isthat the consequences of higher than necessary pressures are not completelyunderstood.
这个问题肯定还会被问到：这些试验如此简单为什么却不能被油漆专家们每天操作？原因很多，其中最重要的原因是高压较之必要的压力所造成的结果不被大家完全理解。
One ofthe important characteristics tout-ed by the manufacturersof airless spray equipment is its improved transfer efficiency compared toconventional spray, as noted in“On the Differences Among Spray Systems, ”JPCL , July, 1999. Transferefficiency refers to the percentage of sprayed paint that actually sticks tothe surface. However, transfer efficiency is reduced by excessive pressure. Thepaint has excess energy when it reaches the surface, causing it to bounce offrather than stick to the surface. Excessive pressure wastes paint and increasestip wear, the problems of which have already been discussed.
受到制造商热捧之一的无气喷涂设备，其较之传统的手动喷涂改良了涂料传输效率。其正如JPCL在1999年7月所提出的的“
喷淋系统之间的差异”一点。传输效率指的是实际雾化的涂料粘附在工件表面的百分比。然而过高的操作压力却会使传输效率降低，当雾化的涂料抵达工件表面因涂料能量过剩导致其从工件表面反弹出来而不会被粘附。现已被证实：压力过大会造成涂料浪费且加快喷嘴磨损速率。 Highspray pressure also increases the prevalence of dry spray by partially dryingthe paint droplets before they reach the sur-face. Dry spray, in turn, canresult in poor film formation because the coating will not be smooth andcontinuous. When this hap-pens, the dry spray needs to be sanded out,and a new layer of coating applied. The cost can be very high.
高喷涂压力也会提高干喷的风险，在漆滴到达工件表面前使涂料变干。干喷，会因涂层不平整且不连续而造成涂层过薄等诸多问题，造成的成本代价也相当高。修整干喷缺陷需要用砂纸打磨并且涂覆上一层新的涂层。代价确实是太高了！
Settingthe proper pressure seems so easy, but it is so often ignored. An applica-torcan simply turn the pump to the maxi-mum pressure and spray. It will work — notideally — but it will work. Dry spray is one of the most common coating defectsencountered with spray application, and it is one of the simplest things tocorrect.
设置合适的操作压力看似容易，但却经常被大家所忽视，喷涂操作员可简单的将泵压调至最大之后喷涂。这样做可行—虽不是很理想—但确实有效果。干喷是喷涂操作中最常见的涂膜缺陷之一，同时也是最容易纠正的缺陷。
ProperTip Selection
选择合适的喷嘴
Theproper tip is determined by the viscosi-ty of the material, the size of theobject to be painted and sometimes the particle size of the raw materials usedto produce the paint.
喷嘴的选择依据原料的粘度，被喷涂物件的尺寸和用于生产涂料所使用原料的颗粒大小。
However,before proper tip selection can be discussed, it is necessary to discuss howtip sizes are designated. There are two important characteristics to airlesstips. The first is the orifice size of the tip. This repre-sents the diameterof the hole if it were a perfect circle; thus, the larger the orifice, thelarger the hole in the tip. The second is fan width. Different manufacturersuse different methods of denoting fan width. In some cases the fan width isdesignated by the angle of the material as it exits the tip. A 20-degree fan isquite narrow, while an 80-degree fan results in a wide pattern. A tip designatedas 4-19 would be one with a 40-degree fan and a 0.019 thousands of an inchorifice.
然而，在讨论怎么选择合适喷嘴之前，有必要先讨论下喷嘴的设计。无气喷嘴有2个特点，分别是：1.喷嘴的孔口尺寸。假设它是一个完美的圆形的话，孔口尺寸就可以洞口的直径来表示。因此，孔口越大，喷嘴的洞口就越大。2.扇形面宽度。不同制造商使用不同方法来表示扇形面宽度。某些情况下扇形面宽度依据原料从喷嘴喷出的角度来设计的。一个角度为20度的扇形面太窄，但角度为80度的又太宽。喷嘴设计：4-19其意思为：，40度的扇面，喷嘴孔口0.019英寸。
One ofthe first rules in tip selection is that the thinner (lower viscosity) thematerial that is to be applied, the smaller the orifice size needed. Accordingto equipment manu-facturers, the best rule is to use the widest fan and thesmallest orifice size that is prac-tical.
选择喷嘴方法不二法则是：涂料原料越细，则选择越小尺寸的孔口。设备制造商实践证明喷嘴选择最好的方法是使用最宽的扇面和最小的孔口尺寸。 
It isessential to select the proper tip for the viscosity of the paint being used,the area of surface being
coatedand the particle size of the raw materials used to produce the paint. Courtesyof Graco Inc.
根据即将涂装的表面、用于生产涂料的原料的颗粒大小和所用的涂料粘性而选择一个合适的喷嘴是非常重要的。
Thesize of the object being painted must also be considered when selecting a tip.On a project in a fabrication shop, for instance, a crew was painting steelcomponents fabri-cated from 3-inch by 3-inch (7.5-cm by 7.5-cm) angle iron.They were using a 50-degree fan. When asked why, their response was verysimple: “It’s what we always use, and besides it’s all we got.” This tipresulted in the use of about two gallons (7.5 litres) of paint and about 10minutes of labor per component. But most of the paint was being sprayed intothe air due to the length of the spray pattern. Obviously, reducing the fanwidth to a 10- or 20-degree fan could have reduced paint waste and consumptionby at least half. (It is interesting to note that, in this case, thefabrication shop could have further reduced its waste and saved money by usingconventional application methods. The cost of the paint wasted by usingair-less spray was more than the cost of the additional labor required by theuse of con-ventional equipment.)
选择喷嘴时，被涂装物品的尺寸也需要考虑。举例说明：建造车间实施过的一个项目。一组人员正在喷涂3*3 英寸（7.5*7.5cm）的焊接的钢构件。他们当时用的是50度的扇面，当我问为什么这么用时？他们回答的很简单：我们一直是这么用的而且我们也是这么学的。结果每个组件用了大约2加仑(7.5公升)的涂料、10分钟的人工涂装。但大部分的涂料因喷幅长度而喷到了空气中。显然，减少10-20度的喷幅就可以减少涂料浪费，并且至少能少消耗一半的涂料。（有趣的是组装车间因使用传统的手工操作涂装，减少了浪费节省了金钱。使用无气喷涂浪费的涂料比需要额外劳动力用传统的手工设备操作还要多。）
Finally,sometimes the paint itself has par-ticles of sufficient size that require spraytips with a minimum opening size. Opening size is different from orifice size.The actual opening of an airless tip is in the shape of an eye. The orificesize is the width of the eye (the x direction). The height of the eyedetermines the fan width. The smaller the height of the eye, the longer the fanpattern will be. Think of it as simply squeezing the same size round pattern aspreviously described. Sometimes, it is possible to solve plugging problems dueto particles in the paint simply by reducing the fan width, since the openingdid not have to be “squeezed” as tight. Given the same size orifice, the narrowerthe fan is, the larger the actual opening.
最后，有时涂料本身的微粒占有一定的空间，这时就需要喷嘴上附带一个最小的开口尺寸。开口尺寸和喷嘴直径不同。无气喷嘴的实际开口尺寸和眼睛的形状相同，喷嘴直径相当于眼睛的宽度（确定*方向）。眼睛的高度确定了喷幅的宽度。眼睛的高度越小，喷幅越长。联想一下前面所述：只对相同尺寸的圆形图案施压。这样做有时可能会解决堵塞的问题：因为仅仅是涂料的微粒也会减少喷幅的宽度，也因为开口本无必要被“挤”的那么紧。具有相同尺寸的喷嘴，喷幅越窄，实际的开口越大。
Variabilityin Applied Film Thicknesses
涂膜厚度的多样性
Airlessspray frequently results in coatings applied with more variation in thicknessthan allowed in product data sheets. This prob-lem can be addressed in twoways. First, users must become aware of normal film thickness variation;second, the product data sheets must list achievable limits.
Today’scoatings are being formulated to lower volatile organic compound (VOC)con-tent. This often results in higher volume solids. At the same time,information on film-thickness tolerance on product data sheets has notnecessarily changed.
Thisexample provides a good explana-tion. A project stipulated that the material beapplied in accordance with the manufac-turer’s product data sheet, requiringthe 65% volume solids coating to be applied at 40–65 microns (1.5–2.5 mils)DFT. The owner assumed these were a minimum and maximum and insisted that theapplicator meet this “requirement.” This was a very large project and the onlypractical way to apply the coating was with airless equip-ment. With theairless equipment used, the minimum applied DFT to achieve hiding of the surfacewas actually 50 microns (2 mils). Therefore, 50 microns became the minimum, not40 microns (1.5 mils). At 65% volume solids, the minimum applied WFT would be75 microns (3 mils). Using 75 microns as minimal WFT and a variation of 50 micronsWFT, the overall range is computed as 75 to 175 microns (3 to 7mils), or 125±50 microns (5 ±2 mils).Thus, the expected applied variation in DFT based on65% volume solids is 50 to 115 microns (2 to 4.5 mils), where DFT=% vol-umesolids x WFT.
Areading of 125 microns (5 mils) would be common given complicated shapes. Thisis the best that can be expected! Even under the best of conditions, anapplicator cannot apply coatings to a maximum vari-ability of only 10 microns(0.5 mils) DFT from the average, as was required by this example. Thisconclusion is based on a review of lab data both from paint compa-nies and from independent labs.
Coatingsmanufacturers and owners must realize that while the percent solids by vol-umeof paints has been increasing, the abili-ty of applicators to maintain ±50microns WFT — at best — has not changed. Manufacturers must provide realisticthick-ness ranges on product data sheets and owners must have realisticexpectations for the ranges in the field. Increased volume solids also meansthat coating application by airless spray has become more exacting andapplicators must be aware.
Conclusion
Thequality and economy of airless spray application can be improved by attention tothe equipment and properly setting the
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