Is improper nozzle material costing your time and money?

PVDF Plastics Material for Nozzle 

PVDF nozzle material for food, chemical etching and electronic industries

Key IssuesNozzles are mechanical devices that are used to control thefluid flow characteristics when they enter or leave anenclosed pipe or chamber, through an orifice. The variousfluid flow characteristics that need to be controlled are massand rate of fluid flow, direction, shape, pressure and thespeed of the fluid. Nozzle are also used for dispensingvarious media such as powder, steam, abrasives, adhesive,water chemical, coolants, coating, ink, lubricants.They may look simple enough, but spray nozzles are highlyengineered precision components that can wear over time orsuffer damage during normal operations or even cleaning.There are several factors to influence or shorten the nozzleoperating life, sometimes more than one at the same time :1) Erosion/ Wear : Nozzle wear is indicated by an increase innozzle capacity and by a change in the spray pattern, in whichthe distribution (uniformity of spray pattern) deteriorates andincreases drop size. Choice of a wear resistant material ofconstruction increases nozzle life. Because many single fluidnozzles are used to meter flows, worn nozzles result inexcessive liquid usage.2) Corrosion : spray nozzle material can break down due tothe chemical properties of the sprayed material or theenvirontment. The effect is similar to that caused by erosionand wear, with possible additional damage to the outsidesurfaces of the spray nozzle. Corrosion is material related andcaused by chemical attack. There is a very wide range ofmaterials from which nozzle can be made and the properselection of the nozzle material will minimise problems.

3) Exposure to high temperature : Melting orsoftening of nozzle material establishes maximumtemperature limits. However, these limits must bereduced when corrosion, erosion, oxidation orchemical attack are also present in the givenapplication4) Caking/ bearding : build‐up of material on theinside, on the outer edges or near the orifice iscaused by liquid evaporation. A layer of driedsolids remains and obstructs the orifice or internalflow passages.5) Clogging : unwanted solid particles can block theinside of the orifice. Flow is restricted and spraypattern uniformity disturbed.6) Accidental damage : damage to a nozzle orificecan occur if a spray nozzle is dropped or scratchedduring installation, operation or cleaning7) Improper re‐assembly : some spray nozzlesrequire careful re‐assembly after cleaning toensure that internal components, such as gasket,o‐rings and valves, are properly aligned. Improperre‐assembly causes leaking and inefficient sprayperformance.

Selecting MaterialImproved reliability, proper performance and maximum wear life of a spray nozzle often begin with thecorrect material selection. Corrosion and erosion caused by abrasive wear are the most common factors thatcould lead to degradation of a nozzle’s performance. It is important to select the right nozzle materialdepending on the environmental conditions of the given process. Spray nozzles are generally made of suchmaterials as bronze, stainless steel, or plastic.Brass (Bronze) is the easiest material for nozzle manufacturers to work with and is a common material, butbronze nozzles have insufficient resistance to abrasion at middle/high pressure, and limited resistance tocorrosion by corrosive chemicals.Due to its relatively high abrasion and corrosion resistance, stainless steel is widely employed in nozzlemanufacture. When the liquid to be sprayed or the surrounding atmosphere is corrosive however, spraynozzles made of SUS316 or SUS31L stainless steel, both of which have more resistance to corrosion, are moresuitable.Relatively few types of spray nozzles are manufactured from plastic. Plastic nozzles are useful for sprayingchemicals that corrode metal nozzles too quickly. Unlike metal, plastic materials do not display corrosionrates. That is the corrosion of plastic materials is dependent totally on the material’s chemical resistancerather than an oxide layer, so the material is either completely resistant to a chemical or it deteriorates.Thermoplastics deteriorates is indicated by material softening, discoloration, charring, embrittlement, stresscracking, swelling, dissolving and other effects.

stainless steel and bronze nozzle PVDF plastic nozzle

LEFT: Stainless steel full cone nozzle. RIGHT: samenozzle after spraying with limestone slurry. Theerosion and corrosion occurred in less than 2weeks, demonstrating the need for choosing thecorrect nozzle material to suit the conditions.

Ceramic : Highly resistant to abrasive and provides superior wear resistance in abrasive applications and highpressure. Ceramics have excellent corrosion resistance except in very high pH environments.Polyacetal POM (Polyoxymethylen) : Provide good resistance to alkalis, susceptible to high concentrated acids.Can be used in temperature +90 °C exhibits a high thermal stability and high resistance to hydrolysis. POM showsgood sliding properties and high resistance to wear and tear because of the strength and smooth surface. Thereis a very low risk of stress cracks.Polyvinyldene fluoride (PVDF) : Excellent resistance to strong acid and alkalis, good resistance to wear, resistmany reagents and high temperatures (up to 130°C), susceptible to high temperature above water boiling incombination with concentrated sulphuric and nitric acids. Preferred in industrial spraying applications.Stainless steel : Good resistance to chemicals and provide average wear resistanceBrass  (bronze)  :   Average  resistance  to  most  chemistry  and  poor  wear  resistance,  susceptible  to  corrosion especially with fertilisersPEEK :  is used to replace metals in harsh environments. This highest performance engineered thermoplastic offers excellent resistance to wear, chemicals, fatigue and high temperatures up to 320°F (160°C).

COMPARATIVE WEAR TEST Test Medium : 2.5 % kaolin in water

Wear Test

PVDF Nozzles PVDF (polyvinyldene fluoride), thedurable yet economical fluoroplastic that stands upto wear, heat, and corrosion.PVDF Nozzle for Food IndustryIn general, foods are not corrosive, but consumablefoods like sauces and fruits can have pH rangesbetween 2.0 and 3.5, this can be very aggressiveenvironment over time. PVDF plastics componentsare often machined and used in the processing ofcranberry, hot sauces, alcoholic beverages, limejuices and a few other relatively common foods. Theabrasion resistance of PVDF and its ability to besterilized with various chemicals and steam alsoadds to the attractiveness of this material for food,dairy and beverage applications.PVDF is an extremely pure polymer, physiologicallynon toxic, and meets the european directive90/128/EEC relating plastic material to contact withfoodstuffs. It is particular suitable for high purityapplications handling hot and cold water in thesemiconductor, and pharmaceuticals industries.

Most nozzle are constructed of stainless steel, butsome are made of plastic material such as POM,PVDF, PEEK.

PVDF Nozzle for Etching and Electronic IndustryPVDF nozzles are especially suited to the spraying ofacids during etching operations. And their high thermalstability makes them ideal for high temperaturestripping operations. For spraying corrosive fluids or foroperation in corrosive environtments. PCB (printedcircuoit board) manufacturers are looking for nozzles toincrease product yield. Nozzle made from PVDF materialoffer consistent spray patterns along with superiorchemical resistance, capable of effectively spraying avariety of chloride, acid, basses, oxidizing agent andammonia base etchants, these chemical resistancenozzles can withstand temperatures up to 300 °F at 100psi (149 °C at 7 bar).

Application

PVDF is an outstanding choice as a nozzle material for many reasons:Chemical resistancePVDF is typically resistant to: most acids salts andweak bases, halogens and halogenated solvents,alcohols, oxidants, De‐ionized water, UV and nuclearradiation.Temperature rangePVDF can be used at temperatures as high as 285° F(140°C) depending on the chemical environmentand operating pressures of the system. Like mostfluoropolymers PVDF is inherently flame retardant.Abrasion resistancePVDF is one of the most abrasion resistantfluoropolymers. In abrasion tests PVDF ranks withthe best plastics and in most nozzle applications itwill outlast many metals, PVC and PTFE.Mechanical strengthPVDF is one of the most rigid fluoropolymers.PVDF's exceptional tensile strength allows nozzleconstruction without the thick sections normallyassociated with plastics, while allowing operatingpressures normally available only with metallicmaterials.FDA acceptancePVDF is accepted by the FDA for use in a broadrange of food and pharmaceutical applicationswhere stainless steel was once the only choice.

ConclusionPVDF PROPERTIES DATA SHEETStructure : CrystallineSpecific density : 1.77Water absorption rate (%): 0.03Elongation  at break (%): 50Tensile strength (psi): 5.800Compression strength (psi): 10.000Flexural strength (psi): 7.800Flexural modulus (psi): 260.000Impact (Izod ft. lbs/in): 6.6Hardness: R95Deflection temperature (deg. F)‐@ 66 psi: 300 (150 deg.C)‐@ 264 psi: 190 (90 deg. C)

Utilization temperature (deg. F)‐min: ‐40 (‐30 deg.C)‐max: 310 (150 deg. C)

Melting point (deg. F): 340  (170 deg. C)Coefficient of expansion: 0.000022Arc resistance : 60Dielectrical strength (kV/mm): 22UV resistance : GoodChemical resistance : Excellent

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www.sugison.comwww.grahamika.indonetwork.co.idnozzle for candy filler  PT YUPI INDONESIA

material from pvdf (polyvinyldenfluoride)machining by PT. Maxima Sukses