fluid controls - graco · definitions, examples, and explanations comprise the learning module...

Fluid Controls

Concept and Theory Training

321-038 Rev. B Fluid Controls 10/15/99 9:32 AM Page i

Introduction ...........................................1Overview...............................................................1How to Use this Module..........................................1

Purpose and Types of Fluid Controls in a Fluid Handling System .....................3

Learning Objectives ................................................3Purpose of Fluid Controls........................................3Types of Fluid Controls ...........................................3

Contaminant Control ..............................4Learning Objectives ................................................4Types of Contaminants............................................4Measuring Contaminant Particle Size.....................5Filtration Devices...................................................5

Viscosity Control ..................................12Learning Objectives ..............................................12Viscosity Control Purpose and Methods..................12Relationship Between Temperature and Viscosity.....13Benefits of Using Heat to Control Viscosity ............14Heater Selection Factors ........................................15Types of Heaters....................................................17Designing a Heated Circulating System:General Recommendations ....................................20

Suspension Control ..............................28Learning Objectives ..............................................28Suspension Control Purpose and Methods ..............28Agitators...............................................................29Calculating Circulation Flow Rate .......................32

Pressure Control...................................36Learning Objectives ..............................................36Pressure Control Purpose and Methods ..................36Pulsation Dampeners (Surge Tanks, Suppressors) .....36Fluid Regulators ...................................................37Back Pressure Fluid Regulators..............................38Pressure Relief Valves ............................................39Run Away Valves .................................................40

Flow Control.........................................42Learning Objectives ..............................................42Flow Control Purpose and Methods.......................42Selecting a Flow Control Device............................42On/Off Valves.......................................................43Adjustable Valves ..................................................45Combination Valves ..............................................46

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Table of Contents

Graco, Inc.P.O. Box 1441Minneapolis, MN 55440-1441

©1998, 1995 Graco Inc. Form No. 321-038 Rev. B 5/98 Printed in U.S.A.

Below is a listing of trademarks usedin this document:Graco trademarksVis-con2™

Airgard™

321-038 Rev. B Fluid Controls 10/15/99 9:32 AM Page ii

Introduction

Welcome to Fluid Controls, a learning module in Graco’s concept and theory sales training series. Yourunderstanding of the information in this module provides the basis for further study on specific Gracoproducts. Your ability to successfully promote and sell Graco products depends in part on how well youlearn the basics and then apply this knowledge to addressing your customers’ needs.

While this curriculum best fits the requirements of Graco and distributor sales people, it will also benefit anyone whose job function depends on knowledge of Graco’s products.

OverviewTo be effective in the marketplace, Graco and distributor sales people must have a basic understandingof how to achieve fluid control in a system, including how to control contaminants, viscosity, suspen-sion, pressure, and flow. This module, Fluid Controls, introduces these concepts and shows how theyrelate to the day-to-day world of Graco product selection, recommendation, and sales.

This module assumes participants have a basic understanding of terms and concepts related to fluidproperties and characteristics, expressions of measurement, fluid types, and how to move fluids from a fluid container into and through a fluid handling system.

How to Use this ModuleThe basic concept and theory curriculum consists of a series of self-study modules. As the term self-study implies, you work through the materials on your own at a comfortable pace. Plan sufficient time(approximately 30 minutes) to complete at least one section of a module in a working session.

This module combines a variety of features to make the learning process convenient and productive:

• Learning objectives

• Text

• Charts, illustrations

• Progress checks

• Additional resources

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Learning objectives

Each section of material offers a set of learning objectives. Read the objectives and use them to guide you to the most important concepts. After you finish each section and before you complete the progress check, reread the objectives to confirm that you understand the key concepts.

Text

Definitions, examples, and explanations comprise the learning module text. Read it carefully andreturn for review if necessary.

Charts, illustrations

An important element of any instruction is visualizing the concepts. This module contains graphicsand illustrations to enhance the text material and aid your learning. Where appropriate, the modulealso contains charts that help you organize or summarize information.

Progress checks

Progress checks are self-tests that provide reinforcement and confirm your understanding of important topics. After completing each section of the module, return to review the objectives,and then work through each of the progress check items. Upon completion, check your answersagainst those provided. If you answered any items incorrectly, return to the text and reread the pertinent information.

Additional resources

This module may refer you to other documents or sources that expand on the concepts covered in the module. The reference will include the name of the source and how you can obtain it.

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Purpose and Types of Fluid Controls in a Fluid Handling SystemLearning ObjectivesIn any fluid handling system, three phases occur. In phase one, the fluid is moved from the supply con-tainer into a pump. In phase two, the pump moves the fluid into the system. In phase three, either thepump or a number of other devices control the fluid moving through the system to meet the customer’sor the fluid’s requirements for cleanliness, flow, pressure, and application quality. This module focuseson how to control the fluid to meet your customer’s or the fluid’s requirements.

After completing this section, you will be able to:

• Explain the purpose of controlling fluids in a fluid handling system.

• Name the five major types of fluid controls and categorize them into two main categories.

Purpose of Fluid ControlsYou may recommend controls to help prevent problems or to resolve problems due to variables in the fluid being moved, the customer’s environment, or the system itself. Ideally, you will anticipate the challenges that may occur in a particular system and put appropriate controls in place before the system begins running. If a system is already in place, you will need to analyze the problems the customer is experiencing and recommend controls to resolve those problems.

Types of Fluid ControlsWithin a fluid handling system, we can divide types of controls into two main categories: fluid conditioning controls and physical fluid controls.

Fluid conditioning controls are those controls that impact a fluid’s chemistry or chemical condition.Fluid conditioning controls include:

• Contaminant control

• Viscosity control

• Suspension control

Physical fluid controls are those controls that impact a fluid’s movement through the system. Physicalfluid controls include:

• Pressure control

• Flow control

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Contaminant Control

Learning ObjectivesContaminants in a system can cause a variety of problems that may result in a finished product thatdoes not meet your customer’s requirements. Contaminants are the single largest source of problems in any fluid handling system. The primary means for controlling contaminants in a system is throughthe use of filtration devices. This section discusses types of contaminants often found in fluid handlingsystems and how to control or eliminate those contaminants. After completing this section, you will be able to:

• Explain the purpose of controlling contaminants in a fluid handling system.

• Describe the types of contaminants found in fluids.

• Recognize the terms used to measure contaminant size and filter size.

• List and describe four types of fluid filtration devices.

Types of Contaminants

Water, Oil, and Non-compatible Fluids

When unwanted water, oil, or a non-compatible fluid mixes with a fluid or materials in a system it can cause contamination that results in an undesirable application quality. Contamination most oftenoccurs as the result of a system that is not properly flushed.

Dirt

When dirt particles accumulate in a fluid handling system, they can cause wear to regulators andvalves, gun wear, plugged tips, and imperfections in the finished product. Dirt in the system can also cause premature pump and air motor wear. We define dirt as solid particle contaminants such as dust, soil, dried paint, rust, metal chips, or thread sealing compound.

Air

In many fluid systems, air is the primary contaminant. It can cause aeration, cavitation, and fluid changes.

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Measuring Contaminant Particle SizeWe measure contaminant particles in micrometers (abbreviated as microns), or millionths of a meter.The degree of filtration is expressed in terms of the size, in microns, of the smallest particle that willnot pass through the filter. You may also hear filtration size referred to as mesh, which refers to therating of screen wire. For example, a 30 mesh screen is approximately 500 microns. Conversion tablesare available to help you convert between the two measurements.

For most industrial applications, 50-100 micron filter elements are adequate. For finer filtration, 5-20micron filter elements are available. Typical filter size ratings for air are 5-40 microns, for paint 150-250 microns, and for sealants or adhesives 1000-3000 microns.

See the Filtration section of the Graco Industrial Fluid Handling Products catalog for more informa-tion on the relative size of micronic particles and wire screen data for filters.

Filtration DevicesA variety of filtration devices are available that can be divided into four basic categories:• Pre-filters• Filters that protect the pump inlet• Pump outlet filters that protect downstream components• Hose, gun, and tip filters

Pre-filters

Pre-filters are designed to filter impurities at material supply. Pre-filters can range from 2000-micronto 500-micron for a variety of materials. They are typically the largest micron size filters in a system,used to catch the largest impurities.

Figure 1 Pre-filters are the largest micron size filters in a system, used tocatch the largest impurities.

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Filters That Protect the Pump Inlet

Filters that protect the pump inlet are designed to prevent larger objects from entering and possiblydamaging the pump. These filters are typically of a smaller micron size than pre-filters, and may rangein size from 1000 micron to 250 micron. The most common are in-line ‘Y’ strainers, such as thoseplaced between a feed pump and a proportioning pump, or on an inlet siphon tube.

Figure 2 In-line ‘Y’ strainers are a type of filter designed to prevent largerobjects from entering and possibly damaging the pump.

Pump Outlet Filters That Protect Downstream Components

Pump outlet filters (element type filters) that protect downstream components are designed to captureimpurities exiting the pump. These filters are typically the finest filters in the system. They also havethe most surface area to prevent plugging. See Figure 3 for an example showing in-line ‘Y’ strainersused as pump inlet filters and manifold filters on the pump outlets.

Figure 3 In-line ‘Y’ strainers and manifold filters are designed to controlcontaminants in a fluid handling system.

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Manifold filters

‘Y’ line strainers


Another example of a pump outlet filter is an alert- or indicator-type filter, pictured in Figure 4. Thesefilters have an indicator flag on top that pops up when the valve in the filter element is pushed off itsseat due to contamination. The flag indicates that the filter is in need of maintenance.

Figure 4 Alert- or indicator-type filters have a flag that pops up when thefilter is in need of maintenance.

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Clean Needs maintenance


Hose, Gun, and Tip Filters

Hose, gun, and tip filters are used to catch impurities that originate after the pump. The are usuallyabout 150 micron size filters. Finer size filters may cause frequent plugging. You will achieve bestresults when both the pump outlet filter and gun or tip filter are the same size. These filters protect the finish from contamination and prevent spray tips from plugging.

Figure 5 Hose, gun, and tip filters are used to catch impurities that originate after the pump.

In a system with multiple filters, as you move from the supply container to the applicator the filters’size should be progressively finer (smaller micron size).

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Tip filter

Manifoldfilter

Gun inlet filter

Inline whip hose filter


Progress Check

Directions: After answering the following questions, compare your answers with those provided in theanswer key following this progress check. If you respond to any items incorrectly, return to the text andreview the appropriate topics.

1. Why might you recommend equipment to control the fluid in a fluid handling system? (Select allthat apply.)a. To help prevent or resolve problems that may occur due to variables in the fluid being moved,

the customer’s environment, or the system itself.b. To help the pump move the fluid into the system.c. To meet the customer’s requirements for application quality.d. To meet the fluid’s requirements for cleanliness, flow, or pressure.

2. List each of the five major types of fluid controls under its appropriate category.Fluid Conditioning Controls Physical Fluid Controls

___________________________________ ______________________________________

___________________________________ ______________________________________

___________________________________ ______________________________________

3. Why might you recommend equipment for controlling contaminants in a fluid handling system?(Select all that apply.)a. To avoid a finished product with an undesirable application quality.b. To impact the amount of material used on a product.c. To avoid wear to hoses or tubing, to avoid gun wear, or to avoid plugged tips.d. To help prevent settling out of particles or solids found in some fluids.

4. What types of contaminants are commonly found in fluids?

_____________________________________________________________________________

_____________________________________________________________________________

5. Which of the following are terms used to describe the measurement of contaminant particle sizeor to rate screen wire for filtration devices?a. Millimeters (milicons)b. Micrometers (microns)c. Meshd. Element

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For items 6 through 9, match the filtration device with its description.

Filtration Devicea. Pre-filtersb. Filters that protect the pump inletc. Pump outlet filters that protect downstream componentsd. Hose, gun, and tip filters

Description

___ 6. These filters are designed to capture impurities exiting the pump. They are typically thefinest filters in the system.

___ 7. These filters are designed to prevent larger objects from entering and possibly damaging the pump. The most common are in-line ‘Y’ strainers.

___ 8. These filters are used to catch impurities that originate after the pump. You will achieve best results when these filters are the same size as the pump outlet filter.

___ 9. These filters are designed to filter impurities at the material supply. They are typically thelargest micron size filters in a system, used to catch the largest impurities.

10. In a system with multiple filters, as you move from the supply container to the applicator the filters’ size should be which of the following?a. Progressively coarser (larger micron size)b. Progressively finer (smaller micron size)c. The same size throughout

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Answers to Progress Check1. a, c, d. You might recommend equipment to control the fluid in a fluid handling system to meet

the customer’s or the fluid’s requirements for cleanliness, flow, pressure, and application quality.You might also recommend fluid control equipment to help prevent or resolve problems that mayoccur due to variables in the fluid being moved, the customer’s environment, or the system itself.

2.Fluid Conditioning Controls Physical Fluid Controls

Contaminant Control Pressure Control

Viscosity Control Flow Control

Suspension Control

3. a, c. You might recommend equipment for controlling contaminants in a fluid handling system to avoid wear to hoses or tubing, to avoid gun wear, to avoid plugged tips, and to avoid an undesir-able application quality.

4. Types of contaminants found in fluids include water, oil, and non-compatible fluids, as well as dirt and air.

5. b, c. Micrometers (abbreviated as microns) and mesh are terms used to measure contaminant particle size and to rate screen wire for filtration devices.

6. c. Pump outlet filters that protect downstream components (element type filters) are designed to capture impurities exiting the pump. They are typically the finest filters in the system.

7. b. Filters that protect the pump inlet are designed to prevent larger objects from entering and possibly damaging the pump. The most common are in-line ‘Y’ strainers.

8. d. Hose, gun, and tip filters are used to catch impurities that originate after the pump. You willachieve best results when these filters are the same size as the pump outlet filter.

9. a. Pre-filters are designed to filter impurities at the material supply. They are typically the largestmicron size filters in a system, used to catch the largest impurities.

10. b. In a system with multiple filters, as you move from the supply container to the applicator the filters’ size should be progressively finer (smaller micron size).

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Viscosity Control

Learning ObjectivesViscosity control is one of the fluid conditioning control methods available to help your customerimpact the quality or amount of material used on a product. This section focuses on controlling viscosity with heat. After completing this section, you will be able to:

• Explain the purpose of controlling viscosity in a fluid handling system.

• List the three factors that impact viscosity.

• Explain the relationship between temperature and viscosity.

• List several benefits of using heat to control viscosity.

• Identify five performance factors to consider in selecting a heater.

• Identify several installation factors to consider in selecting a heater.

• Define specific heat and list the approximate specific heat for water or water-borne paints and forsolvent-borne paints.

• Calculate the size heater needed for a specific application.

• List and describe four types of heaters.

• Recognize some of the key material issues and equipment issues that can impact the design of a heated circulating system.

Viscosity Control Purpose and MethodsBy controlling viscosity, your customer can impact the quality or amount of the material used on aproduct. Temperature, solvents, and shear all impact viscosity; by minimizing changes in these, you can minimize changes in viscosity. To maintain the proper viscosity of a material, keep shear stress to a minimum and keep containers closed to the atmosphere to prevent evaporation.

To intentionally change viscosity, you can heat or add solvents. However, material manufacturers arethe experts on the composition and formulation of the paints, sealants and other materials they manu-facture. Material manufacturers may not guarantee the quality or performance of a product that hasbeen altered. Therefore, make sure you consult with the material manufacturer before using heat orsolvent to reduce the viscosity of a fluid.

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Relationship Between Temperature and ViscosityHeat reduces viscosity by causing the fluid molecules to move apart, causing the fluid to become thinner. Heat also helps solvents dissolve or disperse pigments and binders. Materials commonlyheated include:

• Adhesives

• Sealants

• Paints and coatings, including standard enamels, oil paints, lacquers, and varnishes

The impact of heat on a material can vary, depending on the type of material and its solids content.Figure 6 illustrates the effect of heat on the viscosity of a typical high solids paint and a typical enamel paint.

Figure 6 High solids materials are temperature sensitive and will vary inviscosity with only a small change in temperature.

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Benefits of Using Heat to Control ViscosityThere are several benefits of using heat to control viscosity. These benefits will often lower your customer’s expenses or increase productivity.

Using Heat to Control Viscosity in Spray Systems

When heat is used to control viscosity in spray systems, less spray energy is required to atomize,resulting in:• improved transfer efficiency• lower atomization pressures• reduced waste disposal costs• improved finish quality

Using Heat to Control Viscosity in Sealant and Adhesive Systems

In sealant and adhesive systems, the benefits of using heat to control viscosity include:• less pressure required to apply materials• more consistent flow rate at the applicator• reducing viscosity may make it possible to pump and apply materials that would otherwise

be too viscous

Solids By Volume are Not Reduced or Diluted

Another benefit of using heat to control viscosity is that solids by volume are not reduced or diluted (as they are when solvents are used to control viscosity). This means:• volatile organic compound (VOC) requirements are maintained• your customer may be able to apply more coating per pass or reduce the number of passes per

part, reducing labor or increasing production rates• there is less of a chance for “sags” or “runs”

Fluid Viscosity Remains Consistent in Heated Systems

Heated systems are usually closed circulating systems, systems in which the coating material is con-stantly circulated (pumped) through the system. In these systems, the fluid viscosity within the systemremains consistent even if the ambient temperature changes in the application environment. Heatingsystems may also be in-line heating systems that modify the temperature of the material on the way tothe applicator. These in-line (also called dead end) heating systems cannot maintain the same level oftemperature control that circulating systems can.

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Heater Selection FactorsA variety of heaters are available to control the viscosity of a material within a system. To select theheater most appropriate for your customer’s application, you need to consider several factors. Thesefactors can be grouped into three categories: heater performance factors, installation factors, and selection factors.

Heater Performance Factors

The first set of factors you need to consider are related to the heater’s ability to perform. Make sure youanswer these questions before selecting a heater:

CapacityWhat is the heater’s ability to raise temperature with a constant flow rate? For example, can it raisetemperature 30 degrees? 60 degrees?

OvershootWhen you turn off the flow, how high does the fluid temperature go? For example, for certain high-solids materials, a 10 degree overshoot may not be acceptable. Some materials can cure or “bake;” so it is important to check with the material manufacturer.

Cycling TemperatureWhat is the change in fluid temperature with a constant flow rate? For most temperature sensitivematerials, cycling temperature should be less than 5 degrees.

Maximum TemperatureWhat is the maximum temperature the heater is capable of producing?

Pressure DropHow much does the fluid pressure drop through the heater? Minimizing pressure drop across theheater is a good objective.

Installation Factors

You also need to consider what requirements exist for installing the heater. Make sure you know the answer to these questions:

What voltage is available?What safety codes must it comply with?What is its working pressure?Is the material compatible with the heater’s wetted parts?

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Selection Factors

Finally, you need to know the specific heat of the material moving through the system and use thatinformation to calculate the appropriate size heater for your customer’s application.

Specific Heat

Specific heat is the amount of energy required to raise the temperature of one pound of material by one degree Fahrenheit. The specific heat of water and water-borne paints is approximately 1.0. Thespecific heat of a solvent-borne paint is about 0.5. This means that a solvent-borne paint requiresapproximately one-half the amount of energy to raise its temperature as does water or a water-bornepaint. The specific heat of sealants and adhesives varies widely with the materials and fillers used.Check with the material manufacturer for accurate information regarding specific heat.

Calculating Heater Size

You can calculate the size heater you need for an application by using the guideline that, for solvent-borne paints, 70 watts will raise the temperature of a one gallon-per-minute system by one degreeFahrenheit.

For example, consider a 0.5 U.S. gpm (1.9 l/min) system in which a solvent-borne paint needs to beheated to 120˚F (49˚C). The average temperature of the paint is 70˚F (21˚C), so the heater must raisethe temperature 50˚F (28˚C). You would use the following formula to calculate the heater capacity:

Wattage required = 140 x S.H. x ˚F rise x gpm.

(Wattage required = 66 x S.H. x ˚C rise x l/min.)

Use a specific heat (S.H.) of 1.0 for water or water-borne paints and a specific heat of 0.5 for oil or solvent-borne paints. Check with the manufacturer for the exact specific heat of a material.

In the above example, a heater with a capacity of 1750 watts is required.

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Types of HeatersDepending on your customer’s application, you may need to select more than one type of heater.

Supply Heaters

A supply heater is a device that heats the material supply container. In applications where the environ-ment is cold, the material may need to be pre-heated to allow it to flow into the supply pump. Drumheaters (also called band heaters) are common types of supply heaters.

Figure 7 Drum heaters (left) and band heaters (right) heat the supply container.

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Heated Ram Plates (Platens) in Ram Systems

In ram systems, heated platens are used to help pump certain types of materials. These materials typi-cally must be heated to reduce their viscosity so they can flow and be pumped at the available pressure.Platens may also be used to melt a material from a solid to a liquid.

Figure 8 Heated platens are used in ram systems.

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Heated platen


In-line Heaters

In-line heaters are heaters placed directly in the pumping line. They are termed “high mass” or oven-type heaters. The temperature of the heater block is set and maintained much the same as an oven.Fluid running through the lines will reach this temperature if left in the heater long enough.

Figure 9 The Graco Vis-con2 heater is an example of an in-line heater.

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Line (Pipe) Heaters

Heated hose and heat tracing are examples of line heaters. Heated hose is appropriate for applica-tions where the material must maintain a certain temperature to the dispensing device and flexi-bility is required, such as to a spray gun. Heated hoses are only applicable for non-flammable fluids.Flammable fluids require insulated circulating lines. Heat tracing is appropriate for fixed sections ofmetal piping.

Figure 10 Heated hose is one method of maintaining a certain temperature material to a dispensing device.

Designing a Heated Circulating System: General RecommendationsBefore designing a heated circulating system, review these general recommendations and determineany additional information you need from either your customer or the material manufacturer.

Material Issues

Not all materials can be heated. Also, the amount of heat required to impact viscosity varies by material. If you plan to use heat to control viscosity, contact the material manufacturer first.

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Consider the set point temperature of the material and the heater’s set point accuracy. The set pointtemperature is the temperature, recommended by the material manufacturer, at which a material spraysor moves most efficiently. The thermostat on a heater is fixed at the set point temperature for thematerial being moved, but actual temperature may vary from that set point.

The amount of variation from the set point determines the heater’s set point accuracy. If a wide variationin temperature occurs, the viscosity of the fluid in the system will also vary. This variation in viscositymay cause fluctuations in the flow rate and coverage and result in an inconsistent finish on the productbeing sprayed. It is important to remember that, because high solids materials are temperature sensi-tive, they vary greatly in viscosity with only a small change in temperature.

Heat materials within the ranges specified by the material manufacturer. And, heat materials to the lowest temperature required—below the boiling point of the lowest boiling point solvent. If heat is above the boiling point of material solvents, liquid viscosity may not be reduced as expected. Thismeans that heating a material to higher temperatures would use more energy and could cause a poorfinish due to solvent loss.

To maintain the most consistent viscosity, circulation is preferred. A no-flow, dead-end conditioncan cure or bake the material in the heater, which could cause pressure loss, inconsistent viscosity,poor heat transfer and, ultimately, complete plugging. Cleaning baked materials out of a heater is a very difficult task.

Equipment Issues

Configure the return line to flow back into the pump foot valve. To avoid heating the material in thedrum, do not return the material to the supply container. Heating the material in the drum may causesolvent loss and poor finish quality.

To avoid system rupture, provide a means for the fluid to expand by:

• Using flexible hose between the heater and the gun

• Properly sizing the accumulator after the heater

• Setting the pressure relief valve at the maximum working pressure of the system

Install heaters on the drop lines to the guns, rather than on the main circulating loop. A heater’scapacity may not be able to handle the flow in the main circulating line.

Install the heater as close to the gun as possible, to avoid losing heat between the heater and the gun.

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Use a temperature rise versus flow rate chart to select a heater. Temperature rise is the differencebetween the temperature of the material as it enters the heater and its outlet temperature. Operateheaters at lowest possible temperature for maximum heater life. The chart in Figure 11 compares maximum temperature rise to flow rate for a Graco Vis-con2 heater.

Figure 11 Shaded area of chart indicates continuous operation capabilityof one Graco Vis-con2 heater. Use multiple heaters if customer require-ments exceed chart guidelines.

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Progress Check


1. What is the purpose of controlling viscosity in a fluid handling system?

_____________________________________________________________________________

_____________________________________________________________________________

2. Which of the following are factors that impact viscosity?a. Particlesb. Solventsc. Temperatured. Compatibilitye. Shear

3. Heat reduces viscosity by causing the fluid molecules to move together, causing the fluid tobecome thinner.a. Trueb. False

4. When heat is used to control viscosity in a fluid system, less spray energy is required to atomize,resulting in which of the following benefits? (Select all that apply.)a. More consistent flow rate at the applicatorb. Improved transfer efficiencyc. Improved finish qualityd. Greater possibility of applying materials that would otherwise be too viscouse. Less pressure required to apply materials

5. List five performance factors to consider when selecting a heater.

_____________________________________________________________________________

_____________________________________________________________________________

_____________________________________________________________________________

_____________________________________________________________________________

_____________________________________________________________________________

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6. Which of the following are installation factors to consider when selecting a heater?a. What is the specific heat of the material?b. What safety codes does it comply with?c. What is its working pressure?d. What is its ability to raise temperature?e. What voltage is available?

7. Define specific heat and list the specific heat for water or water-borne paints and for solvent-borne paints.

_____________________________________________________________________________

_____________________________________________________________________________

_____________________________________________________________________________

_____________________________________________________________________________

_____________________________________________________________________________

8. Calculate the heater capacity required for a 1.0 U.S. gpm (3.785 l/min) system in which a solvent-borne paint needs to be heated to 100˚F (38˚C) from an average temperature of 70˚F (21˚C).

_____________________________________________________________________________

_____________________________________________________________________________

_____________________________________________________________________________

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For items 9 through 12, match the heater type with its description.

Heater Typea. Supply heatersb. Heated ram platesc. In-line heatersd. Line (pipe) heaters

Description

___ 9. These heaters are used in ram systems to help pump certain types of materials. These materials typically must be heated to reduce their viscosity so they can flow and be pumpedat the available temperature.

___10. These heaters are placed directly in the pumping line. They are termed “high mass,”oven type heaters.

___11. Drum heaters (also called band heaters) are examples of these heaters.

___12. Heated hose and heat tracing are examples of these heaters.

13. Before designing a heated circulating system, you should be aware of some general recommenda-tions that may impact the system design. List two material recommendations and two equipmentrecommendations.

Material Recommendations

_____________________________________________________________________________

_____________________________________________________________________________

Equipment Recommendations

_____________________________________________________________________________

_____________________________________________________________________________

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Answers to Progress Check1. By controlling viscosity, your customer can impact the quality or amount of the material used

on a product.

2. b, c, e. Solvents, temperature, and shear all impact viscosity; by minimizing changes in these,you can minimize changes in viscosity.

3. b. False. Heat reduces viscosity by causing the fluid molecules to move apart, causing the fluid to become thinner.

4. a, b, c, d, e. All of the benefits listed may result when heat is used to control viscosity in a fluid system.

5. List five performance factors to consider when selecting a heater.

Capacity

Overshoot

Cycling temperature

Maximum temperature

Pressure drop

6. b, c, e. Installation factors to consider when selecting a heater include: What safety codes does itcomply with? What is its working pressure? What voltage is available?

7. Specific heat is the amount of energy required to raise the temperature of one pound of material byone degree Fahrenheit. The specific heat of water and water-borne paints is 1.0. The specific heatof a solvent-borne paint is 0.5. This means that a solvent-borne paint requires approximately one-half the amount of energy to raise its temperature as does water or a water-borne paint.

8. Wattage required = 140 x 0.5 S.H. x 30˚F rise x 1.0 gpm(Wattage required = 66 x 0.5 S.H. x 17˚C rise x 3.875 l/min)A heater (or heaters) with a capacity of 2100 watts is required for this example.

9. b. Heated ram plates (platens) are used in ram systems to help pump certain types of materials.These materials typically must be heated to reduce their viscosity so they can flow and be pumpedat the available temperature.

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10. c. In-line heaters are heaters placed directly in the pumping line. They are termed “high mass,”oven type heaters.

11. a. Drum heaters (also called band heaters) are common types of devices that heat the supply container.

12. d. Heated hose and heat tracing are examples of line (pipe) heaters.

13. Before designing a heated circulating system, you should be aware of some general recommenda-tions that may impact the system design. List two material recommendations and two equipmentrecommendations.

Material RecommendationsNot all materials can be heated.Consider the set point temperature of the material and the heater’s set point accuracy.Heat materials within the ranges specified by the material manufacturer.The maintain the most consistent viscosity, circulation is preferred.

Equipment RecommendationsConfigure the return line to flow back into the pump foot valve.To avoid system rupture, provide a means for the fluid to expand.Install heaters on the drop lines to the guns.Install the heater as close to the gun as possible.Use a temperature rise verses flow rate chart to select a heater.

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Suspension Control

Learning ObjectivesSuspension control is a fluid conditioning control method available to help your customer impact thequality or amount of material used on a product. After completing this section, you will be able to:• Explain the purpose of suspension control in a fluid handling system.• List several factors that impact the settling out of particles of a fluid.• Distinguish between initial mixing and maintaining in a fluid handling system.• Distinguish between axial flow, radial flow, and tangential flow impellers on an agitator.• List the disadvantages of vortex flow.• Calculate the circulation flow rate needed for a specific application.

Suspension Control Purpose and MethodsMany of the fluids that flow through fluid handling systems contain particles or solids that must beconstantly mixed to maintain the fluid’s consistency and adhesion characteristics. Examples of thesefluids include: high solids paints, metallic paints, zinc-based paints, and coatings.

Suspension control is the process used to help prevent the settling out of the particles or solids found in these fluids. Suspension control is important for two reasons. First, solid paint particles may clog fil-ters and other system components, resulting in damaged equipment or wasted time to clean thesystem. Second, settling may lead to application problems. For example, in the automotive industry,settling can cause color match problems from one part of a car to another. Suspension control helpsmaintain the fluid within the system as it was designed by the material manufacturer.

Factors That Impact Settling

Several factors impact the settling out of the particles of a fluid. You must consider these factors and select a suspension control method that will create a fluid velocity that is greater than the settling velocity.

Fluid viscosity. In more viscous fluids, the particles settle more slowly.

Fluid density. In heavier fluids, the particles settle more slowly.

Particle density. Heavier particles (like silica) settle more quickly than light particles (like talc or vermiculite).

Particle size and shape. Small, round particles (like silica) settle more quickly that large, flat particles(like mica).

Percentage of solids by volume. The higher the percentage of solids by volume, the more you need to be concerned about settling.

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Initial Mixing Versus Maintaining

Fluid handling systems include components whose role is to create and maintain mixing so the solidsdo not settle out. Tumblers, rollers, and shakers provide initial mixing to get a fluid into a homogenousstate inside the supply container. Once initial mixing is done and a homogenous mixture exists, thathomogeneity must be maintained.

AgitatorsAgitators are devices used to create directional flow to overcome gravity and maintain a homoge-nous mix.

Figure 12 Typical propeller type agitator (left) and agitator with gearreduced drive (right).

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Powersource

Gearreducer

Impeller

Powersource

Drive

Impeller


Agitator Components

A typical propeller type agitator consists of a power source, a drive mechanism, and impellers.

Power source

A common power source is a vane air motor like the one pictured in Figure 12.

Drive mechanism

In agitators with direct drive mechanisms, the direct drive shaft pinned to the vane motor causes it tospin. In agitators with gear reduced drive (pictured on the right in Figure 12), speed is reduced, buttorque is increased for use in more viscous materials.

Impellers

Axial flow, radial flow, tangential flow, and helix blades are available.

Axial flow impellers are the most common and are high speed, direct drive. They are used to agitate fluids up to 2,000 cp. Do not use axial flow impellers in square tanks with flat or concave bottoms.

Radial flow impellers are used with a wide range of material viscosities. They can use tapered blades (also called back swept impellers) with shear sensitive materials like water-borne coatings.

Tangential flow impellers are low speed and operate at close tolerances to a container wall (one-eighth inch to 3 inches). They are used to agitate high volumes of fluids that are typically less than 1,000 cp.

Helix blades are spiral shaped, auger type blades used with bung port access applications. Their circular motion lifts thick solids from the bottom of the drum to mix and maintain suspension.They can be used with viscosities up to 5,000 cp.

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Figure 13 Examples of types of axial, radial, and tangential flowimpellers, as well as helix blades.

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Axial flow Radial flow

Helix blades Tangential flow


Vortex Flow

One thing to be aware of is, if the agitator speed is too high, a vortex forms inside the supply container.This is a concern because:

• The flow of a vortex tends to be laminar, so effective mixing does not occur. (Turbulent flow is the objective with agitation.)

• A vortex traps air in the fluid and can cause spray guns to “spit” in finishing applications,leading to finishing defects.

• A vortex causes vibration and may damage the agitator. (Materials with abrasive fillers can disintegrate the impeller blade over time.)

Calculating Circulation Flow RateAfter the homogenized fluid is pumped into the piping system, it needs enough flow to create a fluid velocity faster than the settling velocity of the solids. For most solvent-borne coatings, the recommended velocity is 60 ft/min (18.3 m/min) in the main piping system and 30 ft/min (9.2m/min) in the drops. To calculate the circulation flow rate use this formula:

3.11 x inside diameter2 x .7854 = 60 ft/min (18.3 m/min) flow rate

For example, consider an application in which the pipe size is 1-inch outside diameter tubing with a 16-gauge (.065 inch) wall. The calculations for this example would be:

Step 1. 3.11 x (inside diameter)2 x .7854

Step 2. 3.11 x (.87)2 x .7854

Step 3. 3.11 x .7569 x .7854

Step 4. 3.11 x .5945

Step 5. 1.849 U. S. gpm (6.99 l/min)

In this example, 1.849 U. S. gpm (6.99 l/min) is required to achieve a flow rate of 60 ft/min (18.3 m/min).

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Progress Check


1. Define suspension control and explain why it is important in a fluid handling system.

_____________________________________________________________________________

_____________________________________________________________________________

_____________________________________________________________________________

_____________________________________________________________________________

2. List at least three factors that impact the settling out of particles of a fluid.

_____________________________________________________________________________

_____________________________________________________________________________

_____________________________________________________________________________

3. Explain the difference between initial mixing and maintaining in a fluid handling system.

_____________________________________________________________________________

_____________________________________________________________________________

_____________________________________________________________________________

_____________________________________________________________________________

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For items 4 through 7, match the impeller or blade type with its description.

Impeller or Blade Typea. Axial flow impellersb. Radial flow impellersc. Tangential flow impellersd. Helix blades

Description

___ 4. These are used with a wide range of material viscosities. They use tapered blades (also calledback swept impellers) with shear sensitive materials like water-borne coatings.

___ 5. These are the most common and are high speed, direct drive. They are used to agitate fluidsup to 2,000 cp. Do not use these in square tanks with flat or concave bottoms.

___ 6. These are spiral shaped, auger type blades used with bung port access applications. Their cir-cular motion lifts thick solids from the bottom on the drum to mix and maintain suspension.

___ 7. These are low speed and operate at close tolerances to a container wall. They are used to agitate high volumes of fluids that are typically less than 1,000 cp.

8. If the speed of an agitator is too high, a vortex can form inside the supply container. Which of thefollowing are disadvantages of vortex flow? (Select all that apply.)a. The flow of a vortex tends to be laminar, so effective mixing does not occur.b. After the homogenized fluid is pumped into the piping system, a vortex can create additional

settling of fluid particles.c. A vortex traps air in the fluid and can cause spray guns to “spit” in finishing applications,

leading to finishing defects.d. A vortex causes vibration and may damage the agitator.

9. After the homogenized fluid is pumped into the piping system, it needs enough flow to create a fluid velocity faster than the settling velocity of the solids. For most solvent-borne coatings,the recommended velocity is 60 ft/min (18.3 m/min) in the main piping system and 30 ft/min(9.2 m/min) in the drops. Which of the following formulas would you use to calculate the cir-culation flow rate?a. 6.11 x inside diameter2 x .7854 = 30 ft/min (9.2 m/min) flow rateb. 2.11 x inside diameter2 x .7854 = 60 ft/min (18.3 m/min) flow ratec. 3.11 x inside diameter2 x .7854 = 60 ft/min (18.3 m/min) flow rated. 3.11 x inside diameter2 x .7854 = 30 ft/min (9.2 m/min) flow rate

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Answers to Progress Check

1. Suspension control is the process used to help prevent the settling out of the particles or solidsfound in these fluids. Suspension control is important for two reasons. First, solid paint particlesmay clog filters and other system components, resulting in damaged equipment or wasted time to clean the system. Second, settling may lead to application problems.

2. Several factors impact the settling out of the particles of a fluid. They include: fluid viscosity, fluiddensity, particle density, particle size and shape, and percentage of solids by volume.

3. Fluid handling systems include components whose role is to create and maintain mixing so thesolids do not settle out. Tumblers, rollers, and shakers provide initial mixing to get a fluid into a homogenous state inside the supply container. Once initial mixing is done and a homogenousmixture exists, that homogeneity must be maintained. Agitators are devices used to create thedirectional flow that overcomes gravity and maintains a homogenous mix.

4. b. Radial flow impellers are used with a wide range of material viscosities. They use tapered blades(also called back swept impellers) with shear sensitive materials like water-borne coatings.

5. a. Axial flow impellers are the most common and are high speed, direct drive. They are used to agitate fluids up to 2,000 cp. Do not use these in square tanks with flat or concave bottoms.

6. d. Helix blades are spiral shaped, auger type blades used with bung port access applications. Theircircular motion lifts thick solids from the bottom on the drum to mix and maintain suspension.

7. c. Tangential flow impellers low speed and operate at close tolerances to a container wall. They areused to agitate high volumes of fluids that are typically less than 1,000 cp.

8. a, c, d. The flow of a vortex tends to be laminar, so effective mixing does not occur. A vortex trapsair in the fluid and can cause spray guns to “spit” in finishing applications, leading to finishingdefects. A vortex causes vibration and may damage the agitator.

9. c. To calculate the circulation flow rate, use the formula:

3.11 x inside diameter2 x .7854 = 60 ft/min (18.3 m/min) flow rate

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Pressure Control

Learning ObjectivesPressure control is a physical fluid control method available to help meet your customer’s requirementsfor the application quality of an applied material. After completing this section, you will be able to:• Explain the purpose of pressure control in a fluid handling system.• Match common pressure control devices with their function in a fluid handling system.

Pressure Control Purpose and MethodsIn a fluid handling system, a pump exerts pressure on the fluid in the system to make it flow. Pressureand flow are almost always related in a system. However, factors like viscosity and pressure drop in the system can also impact the pressure-flow relationship. We control fluid pressure to control the flow rate in the system and to meet the customer’s requirements for the application quality of anapplied material. Several devices exist for controlling fluid pressure in a system, including pulsationdampeners, regulators, back pressure regulators, and pressure relief valves.

Pulsation Dampeners (Surge Tanks, Surge Suppressors)Surge tanks are the most common type of pulsation dampener. They are frequently used when a customer finds finish quality unacceptable due to pulsation in the spray pattern or when a fluid regulator by itself cannot handle the pulsation.

Surge tanks minimize pressure and flow variation, especially that caused by pump changeover. Pumpchangeover is the point in the cycle of a reciprocating piston pump when the pump stroke changesdirection. At that point, the fluid in the pump flows backward momentarily and pressure drops.Surge tanks store both fluid and pressure that is released at that critical point in the pump’s cycle.

Air trap surge tanks are used in variety of applications where an acceptable supply of air pressure is available.

Gas charged surge tanks are used where air pressure supply is limited and with moisture sensitivematerials. They are available in both a piston and a diaphragm design.

Figure 14 Air trap surge tank (left) and gas charged surge tank (right).

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Fluid RegulatorsInconsistent pressures in a system can lead to inconsistent material application. Fluid regulators stabi-lize and control fluid pressure. They are designed to feed material to the application tool at the properpressure and to maintain pressure balance within a circulating system. Fluid regulators or back pressurefluid regulators can be used to control gun pressure.

A fluid regulator is a self-adjusting valve that senses fluid pressure at the outlet of the regulator andholds it constant. As inlet fluid pressures fluctuate (from pump changeover), fluid regulators modulateto allow more or less fluid flow through the regulator to maintain the set outlet pressure.

It is important to note that, unlike surge tanks and suppressors, fluid regulators can only reduce pressure. The desired outlet pressure must always be lower than the lowest inlet pressure for a fluid regulator to work effectively. Conversely, if the inlet pressure is typically more than 50 percent higherthan the desired outlet pressure, the regulator will wear out prematurely.

Diaphragm fluid regulators are used in low to medium pressure applications to allow a quickerresponse and high sensitivity to pressure changes.

Piston fluid regulators are used in high pressure applications. While they are less sensitive, they aremore capable of operating in higher pressure ranges.

Figure 15 Fluid pressure regulators stabilize and control fluid pressure ina fluid handling system.

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Back Pressure Fluid RegulatorsInstead of a fluid regulator, a back pressure fluid regulator may be used to stabilize and control thefluid pressure in a system.

A back pressure fluid regulator is a self-adjusting valve that senses the fluid pressure at the inlet of theregulator and holds it constant. As inlet fluid pressures fluctuate, back pressure regulators modulate to allow more or less fluid flow through to maintain the set inlet pressure.

Diaphragm back pressure fluid regulators are used in low to medium pressure applications to allow a quicker response and higher sensitivity to pressure changes.

Less sensitive, piston back pressure fluid regulators are used in high pressure applications.

Figure 16 Back pressure fluid regulators sense the fluid pressure at theinlet of the regulator and hold it constant.

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Pressure Relief ValvesPressure relief valves are designed primarily for safety reasons. They protect equipment by venting pressures that exceed a specified level. In a pumping system, this level is usually the maximum working pressure of the lowest rated component in the system.

When pressure rises above a pre-determined pressure, a valve overcomes a spring tension, dumpingfluid to relieve the pressure until the system returns to the set pressure.

Both spring loaded valves (which are reloadable) and rupture valves (which must be replaced) are available. Rupture valves are susceptible to false rupture from fatigue on cycling loads such as piston pumps.

Figure 17 Pressure relief valves are designed primarily for safety reasons.

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Run Away Valve The pneumatic runaway valve prevents accidental spills from ruptured hoses by recognizing irregularities in the air flow supply and automatically stopping the pump. Spills may occur, but the loss (and mess) will be minimized. The runaway valve also protects the pump from damage that occurs from running at high speeds when the container is empty.

Figure 18 The Graco Pneumatic Runaway Valve.

Pump runaway refers to a rapid acceleration in pump speed, which can result in serious damage to the pump parts caused by overheating and scoring.

Conditions which can cause pump runaway are:

• The fluid supply container is empty, or the fluid supply has been interrupted.

• The pump is cavitating, which means that it has lost its prime because an air pocket has formedaround the pump intake. This happens most frequently with highly viscous fluids.

• A fluid hose downstream from the pump has ruptured, resulting in an increased pump cycle rate.

01341


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When in a runaway condition, the pump requires much more air than during normal operation.The runaway valve senses this rapid increase in the volume of air being used and stops the air flow, stoppingpump operation.

The valve is adjustable for a range of pumps and operating conditions

Graco trademarks its runaway valve as Airgard™.

Figure 19 The pneumatic runaway valve attached to a Graco Bulldog Air Motor.

Air Supply Line

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Run Away Valve


Flow Control

Learning ObjectivesFlow control is a physical fluid control method available to help meet your customer’s requirements for pressure, flow, and application quality. After completing this section, you will be able to:

• Explain the purpose of flow control in a fluid handling system.

• Recognize the factors to consider in selecting a flow control device.

• Distinguish between on/off valves, adjustable valves, and combination valves.

• Give several examples of on/off valves.

• Give several examples of adjustable valves.

Flow Control Purpose and MethodsTwo factors determine the amount of flow in a system: fluid pressure and the total pressure drop in the system. We control flow in a system to meet the customer’s requirements for the pressure, flow,and application quality. The devices that exist for controlling flow in a system fall into three main categories: on/off valves, adjustable valves, and combination valves.

Selecting a Flow Control DeviceYour customer’s application will determine the type and number of devices used in a system. Use thesequestions to help guide your selection and recommendation:

1. What does your customer want the device to do? (Is your customer atomizing? Extruding? Dispensing?)

2. What is the required working pressure of the device?

3. What is the required flow rate of the device?

4. What is the required chemical compatibility of the device? (Solvent-borne? Water-borne?)

5. To what extent must the device be able to withstand abrasives?

6. What is the activating device? (Manually operated? Automatically controlled?)

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On/Off ValvesAn on/off valve is a flow control device with two operating positions: on and off. The valve may beoperated manually, activated by a programmable logic controller (PLC), or meters may be used to mea-sure the volume of fluid and to create a package that turns the valve off after the predetermined volumehas been delivered. Several types of on/off valves are used in fluid handling systems, including: ballvalves, check valves, solenoid valves, and air-operated valves.

Figure 20 An on/off valve is a flow control device with two operating positions: on and off.

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On/off valves

Check valve

Air operated dispense valve


Ball ValvesBall valves are manually operated valves used to isolate a section of a system that requires adjustmentor repairs.

Check ValvesCheck valves allow fluid flow in only one direction.

Solenoid ValvesSolenoid valves (also called electronic valves) are electrically operated valves in which an electricalsignal controls the on/off. They may be operated by on/off switches, relays, solid state relays, and electronic controls such as programmable logic controllers. Solenoid valves are often used to start and stop the flow of air, as well as some fluids.

Solenoid valves may be used as dispense valves for non-abrasive fluids. For example, dispense valvesare used to dispense shots of dielectric material into a capacitor. The lubrication industry also usessolenoid dispense valves to dispense shots of grease into ball bearings. Hot melt guns are anotherexample of solenoid valves.

Air-Operated ValvesIn air-operated valves, an air signal is used to turn the fluid valve on or off.

Color change valves are air-operated valves that are designed to allow many of them to be connectedtogether in a system to handle multiple color changes automatically. They are designed for efficient use and for the least amount of wasted fluid. Automatic dispense and spray guns may also be air-operated valves.

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Adjustable ValvesAdjustable valves have an infinite number of operating positions for flexibility in a variety of applica-tions. Recall from the previous section on pressure control that pressure and flow are almost alwaysrelated. Because of this relationship, by controlling flow with an adjustable valve, we also impact system pressure.

Adjustable valves may be adjusted manually by turning a knob or screw, or automatically from a mechanical or electronic controller. This function can be automated with meters and a control device to create a package that adjusts a needle valve to maintain a predetermined flow rate.

Figure 21 Adjustable valves may be adjusted manually by turning a knobor screw, or automatically from a mechanical or electronic controller.

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Manual Adjustable Valves

By manually turning a screw, you can adjust a tapered needle to slide in and out of the fluid stream.Manual adjustable valves are often used to control the flow rate of fluid in a circulating system. Extru-sion guns are manual adjustable valves and are often used to lay a bead of material. For example, spamanufacturers use manual needle valves to extrude adhesive from 5- and 55-gallon containers to layceramic tile around portable spas.

Automatic Adjustable Valves

A fluid pressure regulator is one example of an automatic, adjustable valve. A diaphragm or spring is used to adjust the valve. In this case, the flow is adjusted to maintain constant pressure. Or, a mater-ial manufacturer may use an automatic needle valve to fill tubes of caulking silicone from a 55-galloncontainer. In this application, a priming piston pump on a ram with heaters would help the flow of the silicone.

Automatic adjustable valves may also be controlled electronically; the valve position is adjusted by acomputer, which also monitors the system flow rate. These type of valves are often used in the roboticapplication of sealants and adhesives in production lines.

Combination ValvesCombination valves can be manually or automatically operated and may be set to be full-on or full-off,or finely adjusted anywhere in between full-on and full-off.

One example of combination valves is airspray guns, including high volume low pressure (HVLP)guns and electrostatic guns. Another example is extrusion guns. Window manufacturers use manualextrusion valves to apply caulking material around windows. In automotive assembly plants, automaticextrusion valves apply material that seals the seams between body sheet metal components.

Figure 22 Extrusion valves are examples of combination valves.

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Progress Check


1. Which of the following statements best describes the purpose of pressure control in a fluid handling system?a. We exert and control pressure on the fluid in the system to help it flow and to meet the fluid’s

and the customer’s application requirements.b. We control the pressure of the fluid in the system to to meet the fluid’s application and quality

requirements.c. We control pressure to control viscosity, pressure drop, and flow rate in the system and to

impact the pressure-flow relationship.d. We control fluid pressure to control the flow rate in the system and to meet the customer’s

requirements for the application quality of an applied material.

For items 2 through 5, match the pressure control device with its description.

Pressure Control Devicea. Surge tanksb. Fluid regulatorsc. Back pressure fluid regulatorsd. Pressure relief valves

Description

___ 2. This pressure control device is designed primarily for safety reasons. It protects equipmentfrom too high pressures by venting pressures that exceed a specified level.

___ 3. This pressure control device is a self-adjusting valve that senses the fluid pressure at the inlet of the regulator and holds it constant. As inlet fluid pressures fluctuate, this devicemodulates to allow more or less fluid flow through to maintain the set inlet pressure.

___ 4. This pressure control device is a self-adjusting valve that senses fluid pressure at the outlet ofthe regulator and holds it constant. As inlet fluid pressures fluctuate, this device modulates toallow more or less fluid flow through the regulator to maintain the set outlet pressure.

___ 5. This pressure control device is frequently used when a customer finds finish quality unac-ceptable due to pulsation in the spray pattern or when a fluid regulator by itself cannothandle the pulsation.

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6. Which of the following statements best describes the purpose of flow control in a fluid handling system?a. We control flow in a fluid handling system to meet the customer’s and the fluid’s require-

ments, and to maintain the pressure to flow relationship.b. We control flow in a system to meet the customer’s requirements for pressure, flow, and

application quality.c. We control flow in a system to meet the fluid’s requirements for flow and application quality.d. We control flow in a fluid handling system to maintain the pressure to flow relationship.

7. List at least three of the five factors to consider in selecting a flow control device.

_____________________________________________________________________________

_____________________________________________________________________________

_____________________________________________________________________________

8. Explain the difference between on/off valves, adjustable valves, and combination valves.

_____________________________________________________________________________

_____________________________________________________________________________

_____________________________________________________________________________

_____________________________________________________________________________

9. In the electronics industry, dispense valves are used to dispense shots of dielectric material into acapacitor. In the lubrication industry, solenoid dispense valves are used to dispense shots of greaseinto ball bearings. Into what category of flow control devices do these valves fit?a. On/off valveb. Adjustable valvec. Combination valve

10. Window manufacturers use manual extrusion guns to apply caulking material around windows. Inautomotive assembly plants, automatic extrusion valves apply material that seals the seamsbetween body sheet metal components. Into what category of flow control devices do these valves fit?a. On/off valveb. Adjustable valvec. Combination valve

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Answers to Progress Check

1. d. We control fluid pressure to control the flow rate in the system and to meet the customer’srequirements for the application quality of an applied material.

2. d. Pressure relief valves are designed primarily for safety reasons. They protect equipment from toohigh pressures by venting pressures that exceed a specified level.

3. c. A back pressure fluid regulator is a self-adjusting valve that senses the fluid pressure at the inletof the regulator and holds it constant. As inlet fluid pressures fluctuate, the back pressure fluid regulator modulates to allow more or less fluid flow through to maintain the set inlet pressure.

4. b. A fluid regulator is a self-adjusting valve that senses fluid pressure at the outlet of the regulatorand holds it constant. As outlet fluid pressures fluctuate, the fluid regulator modulates to allowmore or less fluid flow through the regulator to maintain the set outlet pressure.

5. a. Surge tanks are frequently used when a customer finds finish quality unacceptable due to pulsation in the spray pattern or when a fluid regulator by itself cannot handle the pulsation.

6. b. We control flow in a system to meet the customer’s requirements for pressure, flow, and application quality.

7. Factors to consider in selecting a flow control device include: What does your customer want thedevice to do? (Is your customer atomizing? Extruding? Dispensing?) What is the required work-ing pressure of the device? What is the required flow rate of the device? What is the requiredchemical compatibility of the device? (Solvent-borne? Water-borne?) To what extent must thedevice be able to withstand abrasives?

8. An on/off valve is a flow control device with two operating positions: on and off. Adjustable valveshave an infinite number of operating positions for flexibility in a variety of applications. Combina-tion valves may be set to full-on, full-off, or finely adjusted anywhere between full-on and full-off.

9. a. Solenoid dispense valves fit into the category of on/off valves.

10. b. Manual and automatic extrusion valves fit into the category of combination valves.

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Module Evaluation

The purpose of this Module Evaluation is to help the Graco Technical Communications department determine the usefulness and effectiveness of the module.

Instructions: Please complete the evaluation, tear it on the perforation, and return it Graco TechnicalCommunications Department, P.O. Box 1441, Minneapolis, MN 55440-1441, USA.

1. Based on the objectives, this module:

Significantly exceeded my expectations

Exceeded my expectations

Met my expectations

Was below my expectations

Was significantly below my expectations

2. Why did you select the above rating?

3. How do you plan to use the module information in your job?

4. How do you think the module could be improved?

I verify that I have successfully completed Module No. 321-038

Title Fluid Controls

Signature _________________________________________________

Date _______________________

Fluid Controls


GracoTechnical Communications Dept.P.O. Box 1441Minneapolis, MN 55440-1441 U.S.A.

(fold here)

(fold here)


This module was developed by the Graco Technical Communications Department with assistancefrom the following individual:

Dan Accettura

Mike Kline

Ken Lehrke

Barry Yarnell

Bruce McIntosh

The Graco Concept and Theory Training program consists of the following topics:

Fluid Basics

Atomization

Electrostatic Spray Finishing

Safety

Airspray Technology

Fluid Types: Paints and Other Coatings

Fluid Types: Lubricants

Fluid Types: Sealants and Adhesives

Airless Atomization

Spraying Techniques

Transfer Efficiency

Fluid Movement

Fluid Controls

Pumps

Motors and Power Sources

Plural Component Paint Handling

Plural Component Sealant and Adhesive Handling

Paint Circulating Systems

Automatic Finishing

Lube Reels and Dispense Valves

Lube Metering Systems

Electronic Fluid Management Systems

Graco, Inc.P.O. Box 1441 - Minneapolis, MN 55440-1441©1998, 1995 Graco Inc. Form No. 321-038 Rev. B 5/98 Printed in U.S.A.

Fluid Controls


fluid controls - graco · definitions, examples, and explanations comprise the learning module...

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