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  • Double Diaphragm Pumps

    Concept and Theory Training

  • Introduction ........................................... 1Module Purpose ..................................................... 1Primary Audience .................................................. 1Benefits to You ........................................................1Objectives ...............................................................1How Do I Use This Module? ...................................1What Materials Do I Need? ....................................1

    Double Diaphragm Pump........................ 2Component Identification and Function ..................2Progress Check ........................................................4

    Double Diaphragm Pump Operation ....... 6Moving Fluid.........................................................6Progress Check ........................................................8Air Flow Operation ..............................................10Air Flow with Mechanical Triggering ...................10Progress Check ......................................................13

    Pilot Operated Triggering ......................15

    Whole Pump Operation ......................... 19Progress Check ......................................................21Summary..............................................................23Materials of Construction......................................23

    Pump Application................................. 26

    Advantages .......................................... 27Pump Advantages .................................................27Air Valve Advantages............................................27Limitations...........................................................28Trade Names ........................................................28Self Check .............................................................29Additional Resources .............................................32

    Double Diaphragm Pumpsi

    Table of Contents

    Graco Inc. is registered to I.S. EN ISO 9001.

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

    1996 Graco Inc. Form No. 321-048 1/96 Printed in U.S.A.

    Husky is a registered trademark of Graco Inc.Teflon,Viton, and Hytrel are registered trademarks of Du Pont.Kynar is a registered trademark of AtochemNorth America, Inc.Santoprene is a registered trademark of Monsanto.

  • Introduction

    Module Purpose The purpose of this module is to help you understand the design and operational characteristics ofDouble Diaphragm Pumps.

    Primary AudienceThe primary audience for this module is for anyone who would like a better understanding of double diaphragm pumps.

    Benefits to YouThe benefits to you of successfully completing this module include:

    gaining knowledge of double diaphragm pump design and operation.

    being able to understand and satisfy the customers pumping application requirements.

    ObjectivesAfter completing this module, you should be able to:

    Explain the theory of operation of Graco Double Diaphragm Pumps.

    Know the advantages of the Graco Double Diaphragm Pumps.

    How Do I Use This Module?This module is designed for you to use at your own pace and at the time you most need it in your job.You can also use the module as a reference after completing it.

    What Materials Do I Need?In addition to this booklet, you will also need these items to complete this module:

    Fluid Basics, Form No. 321-026

    Moving Fluids, Form No. 321-037

    Fluid Controls, Form No. 321-038

    Double Diaphragm Pumps 1

  • Double Diaphragm Pump

    Double Diaphragm Pumps use compressed air as the power source. They are frequently used for fluidtransfer, low pressure spray, and other lower pressure applications requiring less than 120 psi (8.5 bar).

    Component Identification and Function

    Figure 1 Double Diaphragm Pump Component Identification.

    Double Diaphragm Pumps2

    Outlet Manifold

    Check Valve

    Diaphragms

    Fluid Housing

    Inlet Manifold

    Air Chamber

    Air Valve

    Exhaust Port

    Muffler not Pictured

    05577

  • Air Chambers

    Compressed air flows into or out of the air chambers. The pump has a Right and Left Air Chamber.

    Fluid Housings

    The fluid being pumped will flow through the fluid housings. Each pump has a Right and Left Fluid Housing.

    Diaphragms

    Diaphragms separate the air chambers and fluid housings in the pump. The diaphragm is a materialthat will flex with increasing or decreasing air pressure. A common shaft connects the two diaphragms.

    Inlet Manifold

    Fluid flows from the fluid container through the inlet manifold either to the right or left fluid housing.

    Outlet Manifold

    Fluid flows out of the right or left fluid housing past the check valves, then through the outlet manifold.

    Air Valve

    The air valve directs compressed air to either the right or left air chamber. The air valve consists of a triggering mechanism, a valve cup, and a valve plate. The air valve directs compressed air through aport to one of the air chambers while the opposite air chamber is directed to the exhaust port.

    Check Valves

    A double diaphragm pump has four fluid check valves, two inlet check valves and two outlet checkvalves. The check valves control the fluid flow through the fluid housings and manifolds of the pump.Most double diaphragm pumps use ball type check valves. For a thorough explanation of check valveoperation refer to the Fluid Controls module.

    Muffler

    The muffler minimizes the noise of the exhaust air. Different mufflers provide different levels of noise reduction.

    Wetted Parts

    The wetted parts include all parts that come into contact with the pumped fluid. They include the inletmanifold, ball checks and seats, diaphragms, fluid housings, and outlet manifold.

    Double Diaphragm Pumps 3

  • Double Diaphragm Pumps4

    ____________

    ____________

    ____________

    ____________

    ____________

    ____________

    ____________

    ____________

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    Progress Check

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

    1. Graco Double diaphragm pumps can be driven by air, hydraulic, or electric motors.

    a. True

    b. False

    2. Fill in each space provided with the name of the component.

  • Double Diaphragm Pumps 5

    Answers to Progress Check

    1. False

    2. (See Figure 1.)

  • Double Diaphragm Pump Operation

    To help clarify the operation of the Double Diaphragm Pump we will divide the operation as follows.First we will describe the fluid flow. Then we will describe the air flow. Then we will describe the airvalve triggering mechanisms used in Graco Double Diaphragm pumps. We will refer to the pumpoperation as the right or left. This is to aid in description only and bears no significance in a realapplication.

    Part 1. Moving FluidCompressed air flows into the right air chamber, causing the right diaphragm to flex. This expansioncreates a high pressure in the right fluid housing equal to the air pressure applied to the pump. Theinlet check valve (4) of the right fluid housing closes, the outlet valve (2) opens, and the fluid ispumped through the outlet manifold. The pump shaft moves right creating a vacuum in the left fluidhousing. The left inlet check valve (3) opens, the left outlet valve (1) closes, and the fluid flows into theleft fluid housing. See Figure 2 for an illustration of the cycle.

    Figure 2 Pumping Fluid: movement to the right.

    Double Diaphragm Pumps6

    Fluid Outlet

    Fluid Inlet

    05578

  • Double Diaphragm Pumps 7

    At the end of the pump stroke the air valve switches and compressed air will flow into the left airchamber, causing the left diaphragm to flex. The inlet check valve (3) of the left fluid housing closes,the outlet valve (1) opens, and the fluid is pumped through the outlet manifold. The pump shaftmoves left creating a vacuum in the right fluid housing. The right outlet valve (2) closes, the right inletcheck valve (4) opens, and the fluid flows into the right fluid housing. See Figure 3.

    Figure 3 Pumping Fluids: movement to the left.

    Fluid Outlet

    Fluid Inlet

    05579

  • Double Diaphragm Pumps8

    Progress Check

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

    1. The flow of fluid is controlled by

    a. Check valves.

    b. Valve cup.

    c. The muffler.

    2. Compressed air pressurizes the pump fluid to a pressure _________________ the applied pressure.

    a. equal to

    b. much higher than

    c. much lower than

  • Double Diaphragm Pumps 9

    Answers to Progress Check

    1. a.

    2. a.

  • Double Diaphragm Pumps10

    Part 2. Air Flow OperationTo understand how the pump functions, you must understand how it is controlled or triggered. Thereare two types of air valve triggering mechanisms used in Graco pumps: mechanically actuated and pilotoperated.

    Air Flow With Mechanical TriggeringWith the air valve in the left position, the left air chamber is connected to the exhaust port, compressedair will flow directly into the right air chamber. The diaphragm shaft moves to the right.

    Figure 4 Air Valve In The Left Position.

    Compressed Air Inlet

    Air Valve Cup

    Air Exhaust

    05573

  • Do

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