Graco 312185S User Manual

Instructions - Parts

312185S

MD2 Valve

For use with disposable mixers to dispense a variety of sealants and adhesives. For professional use only.

120 psi (0.84 MPa, 8.4 bar) Maximum Air Inlet Pressure

Important Safety Instructions

Read all warnings and instructions in this manual. Save these instructions.

See page 2 for model information, including maximum working pressure and approvals.

TI9964A

MD2 Valve Models

Contents

MD2 Valve Models . . . . . . . . . . . . . . . . . . . . . . . . . . 2

Warnings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

Component Identification . . . . . . . . . . . . . . . . . . . . 5

Features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

Installation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

Setup . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

Maintenance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

Troubleshooting . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

Repair . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

Parts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

Accessories . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

Technical Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29

Dimensions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29

Graco Standard Warranty . . . . . . . . . . . . . . . . . . . 30

Graco Information . . . . . . . . . . . . . . . . . . . . . . . . . 30

MD2 Valve Models

MD2 Valves

Maximum Working Pressure

Part No.

255179

255180 1:1 Hard seat, non-adjustable snuff-back

255181 Wide ratio, soft seat, adjustable snuff-back

255182 Wide ratio, hard seat, non-adjustable snuff-back

255183 2000 psi (13.8 MPa, 138 bar) Cold spray/joint fill valve

255206 120 psig (0.84 MPa, 8.4 bar) Air trigger

255208 3A @ 28 VDC Electric air actuated

255249 0.5 @ 28 VDC Electric actuated lever

3000 psi (20.7 MPa, 207 bar

psi (MPa, bar) Description

1:1 Soft seat, adjustable snuff-back

MD2 Valve Handles

Model Selection

The following table provides a summary of the MD2 dispense valves that are described in this manual.

Type Description

Hand held valves with

internal air trigger

Hand held valve with

electric switch

Wide ratio valves The wide ratio MD2 valve has a center injection tip. This feature is helpful with wider

Hard seats Carbide seats and hardened needles are good for abrasive materials and stall against

Soft seats UHMWPE seals are good for precise snuff-back control.

2 312185S

The internal air trigger controls the air piston that operates the MD2 valve. A pilot port can be used to control a pump motor.

The switch signals the customer’s controller to open and close the ports on the MD2 valve using a remote 4-way air control valve which is not included.

ratio applications, specifically when the low volume material is a much lower viscosity than the high volume material. Frequent cleaning intervals may be required to maintain the tip.

pressure applications.

Warnings

The following warnings are for the setup, use, grounding, maintenance, and repair of this equipment. The exclamation point symbol alerts you to a general warning and the hazard symbol refers to procedure-specific risk. Refer back to these warnings. Additional, product-specific warnings may be found throughout the body of this manual where applicable.

WARNING

SKIN INJECTION HAZARD

High-pressure fluid from dispense valve, hose leaks, or ruptured components will pierce skin. This may look like just a cut, but it is a serious injury that can result in amputation. Get immediate surgical

treatment.

• Do not point dispense valve at anyone or at any part of the body.

• Do not put your hand over the end of the dispense nozzle.

• Do not stop or deflect leaks with your hand, body, glove, or rag.

• Follow Pressure Relief Procedure in this manual, when you stop spraying and before cleaning, checking, or servicing equipment.

EQUIPMENT MISUSE HAZARD

Misuse can cause death or serious injury.

• Do not operate the unit when fatigued or under the influence of drugs or alcohol.

• Do not exceed the maximum working pressure or temperature rating of the lowest rated system component. See Technical Data in all equipment manuals.

• Use fluids and solvents that are compatible with equipment wetted parts. See Technical Data in all equipment manuals. Read fluid and solvent manufacturer’s warnings. For complete information about your material, request MSDS forms from distributor or retailer.

• Check equipment daily. Repair or replace worn or damaged parts immediately with genuine manufacturer’s replacement parts only.

• Do not alter or modify equipment.

• Use equipment only for its intended purpose. Call your distributor for information.

• Route hoses and cables away from traffic areas, sharp edges, moving parts, and hot surfaces.

• Do not kink or over bend hoses or use hoses to pull equipment.

• Keep children and animals away from work area.

• Comply with all applicable safety regulations.

TOXIC FLUID OR FUMES HAZARD

Toxic fluids or fumes can cause serious injury or death if splashed in the eyes or on skin, inhaled, or swallowed.

• Read MSDS’s to know the specific hazards of the fluids you are using.

• Store hazardous fluid in approved containers, and dispose of it according to applicable guidelines.

• Always wear impervious gloves when spraying or cleaning equipment.

PERSONAL PROTECTIVE EQUIPMENT

You must wear appropriate protective equipment when operating, servicing, or when in the operating area of the equipment to help protect you from serious injury, including eye injury, inhalation of toxic fumes, burns, and hearing loss. This equipment includes but is not limited to:

• Protective eyewear

• Clothing and respirator as recommended by the fluid and solvent manufacturer

•Gloves

• Hearing protection

312185S 3

Warnings

WARNING

FIRE AND EXPLOSION HAZARD

Flammable fumes, such as solvent and paint fumes, in work area can ignite or explode. To help prevent fire and explosion:

• Use equipment only in well ventilated area.

• Eliminate all ignition sources; such as pilot lights, cigarettes, portable electric lamps, and plastic drop cloths (potential static arc).

• Keep work area free of debris, including solvent, rags and gasoline.

• Do not plug or unplug power cords, or turn power or light switches on or off when flammable fumes are present.

• Ground all equipment in the work area. See Grounding instructions.

• Use only grounded hoses.

• Hold gun firmly to side of grounded pail when triggering into pail.

• If there is static sparking or you feel a shock, stop operation immediately. Do not use equipment until you identify and correct the problem.

• Keep a working fire extinguisher in the work area.

4 312185S

Component Identification

FIG. 1: Component Identification

Key:

A Snuff-back adjustment knob (soft seat versions only) B 1/8 in. npt (f) air to close (O). C 1/8 in. npt (f) air to open (I). D 9/16 straight thread o-ring boss “B” fluid inlet (low volume) E 9/16 straight thread o-ring boss “A” fluid inlet (high

volume) F Zerk grease fitting G Nosepiece with 7/8-9 bell outlet H Air cylinder

TI10391A

312185S 5

Features

Electric Switch Valve

Series A handle shown

TI10383A

Normally open momentary contact switch

Note: The Trigger/Lever activates an electrical switch in the handle, which activates a remote 4 way solenoid valve. Bring an “OPEN” air signal to the 1/8 in. npt(f) port (I) on this side of the valve, and a “CLOSE” signal to the port (O). See Accessories, page 23, to order fittings and tubing.

Pneumatic Valve

1/4 in npt (f) air inlet

TI10407A

The 1/8 in. npt (f) port (I) can be used to send an “ON” signal back to a pump pilot or control. See F

IG. 1.

Electric Actuated Lever Valve

FIG. 2: Features of the MD2 Valves

TI10409A

6 312185S

Installation

Grounding

The following grounding instructions are minimum requirements for a basic dispensing system. Your system may include other equipment or objects which must be grounded. Check your local electrical code for detailed grounding instructions for your area and type of equipment. Your system must be connected to a true-earth ground.

• Pump: ground the pump by connecting ground wire

and clamp as described in your separate pump

instruction manual.

• Air compressors and hydraulic power supplies:

ground the equipment according to the manufac-

turer's recommendations.

• Fluid hoses: use only grounded fluid hoses with a

maximum of 500 feet (150 m) combined hose length

to ensure grounding continuity. Check the electrical

resistance of your fluid hoses at least once a week.

If your hose does not have a tag on it which speci-

fies the maximum electrical resistance, contact the

hose supplier or manufacturer for the maximum

electrical resistance limits, replace the hose immedi-

ately.

• Dispensing valve: ground the valve by connecting

it to a properly grounded fluid hose and pump.

• Fluid supply container: ground according to your

local code.

• Flammable liquids in the dispense area: must be

in approved, grounded containers. Do not store

more than the quantity needed for one shift.

• All solvent pails used when flushing: ground

according to local code. Use only metal pails, which

are conductive. Do not place the pail on a non-con-

ductive surface, such as paper or cardboard, which

interrupts the grounding continuity.

• To maintain grounding continuity when flushing or

relieving pressure, hold a metal part of the valve

firmly to the side of a grounded metal pail, then trig-

ger the valve.

How to Use the Valve Trigger Safety

1. If you are using one of the hand-held versions of the valve, lock the valve trigger safety by turning the latch to a right angle with the gun body. See F

2. To unlock the valve trigger safety turn it parallel with the gun body.

LOCKED

TI10442A

FIG. 3

UNLOCKED

IG. 3.

TI10441A

312185S 7

Setup

Fluid and Air Connections

9/16 Straight Thread O-Ring Boss Fluid Inlets

There is one fluid inlet on the A-side and one fluid inlet on the B-side. The fluid inlets are located on the side of the valve and swivel to permit various mounting and hose configurations.

1/8 npt(f) Air Inlets

The machine mount valves and the electric switch hand-held valves have an on port (I) and off port (O), which are operated by a remote 4-way air control valve. Use one of the two air inlets located on the bottom and on the back of the valve.

The air switch hand-held valves have a single air inlet with an internal 4-way spool which operates the air piston.

See Accessories on page 19, to order air control valves and tubing.

Inlet Check Valves

Inlet check valves are recommended on the fluid inlets where viscosity allows. An inlet check valve prevents back-flow or crossover when the mixer is plugged or one fluid is much lower viscosity than the other. When required, a high crack pressure check valve is installed to maintain back-pressure on low viscosity fluids.

See Accessories on page 19 for a list of check valves.

Balancing the System

Selecting Hoses

Hoses between your proportioner and the MD2 valve should be selected carefully. Many factors effect hose selection.

1. Fluid Compatibility: Fluid must not degrade the core material or end fittings of the hose. Nylon or PTFE cores are commonly used for chemical compatibility. If your fluid is moisture sensitive you should use PTFE or Moisture-Lok hoses.

2. Pressure Rating: Be sure hoses have a working pressure rating above the pressure capability of the system.

3. Compressibility: Hoses, especially nylon paint hoses, expand with an increase in pressure. A pressure change in the system may cause a volume change, which can appear as a ratio error with wide mix ratios. Compressible hoses absorb pressure spikes which is helpful to the operator during an application, such as trying to lay a bead.

4. Internal Diameter: Small I.D.'s create higher back pressures, lower flows, and small retained volume. Typically hose I.D.'s are selected for:

a. System Pressure Balance. “A” pressure drop

vs. “B” pressure drop.

b. Volume Balance. A:B volume ratio vs. Hose

retained volume.

c. Flexibility and weight for operator or robot.

d. Overall Pressure Drop. Pressure drop should be

minimum possible within the above guidelines.

A proportioner is used to feed the two-component dispense valve. The system must be pressure balanced to avoid “lead-lag” ratio errors when starting and stopping the flow.

Balancing is done by hose sizing or inlet check restriction. A properly balanced system has near equal back-pressure on the gauges when flowing without a mixer installed.

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5. Length: Hoses normally are kept as short as practical to minimize pressure drop and compressible volume. 10 ft (3.1 m) is recommended for reciprocating pump systems.

System Start-up

When initially loading the fluids through the system, leave the mixer off until both fluids flow freely from the nose piece without any air. This prevents cross contamination from having fluid on one side pushing back up the other side.

Mixer Selection

Disposable mixers are available from 3/16 in. I.D. to 1/2 in. I.D. in lengths from 12 elements to 36 elements. In general, wide viscosity or mix ratios require more mix elements. Small I.D. mixers produce lower flow, higher back-pressure, and waste little material. Large I.D. mixers produce higher flow, lower back-pressure, and fewer lead-lag ratio errors. Different mixers can have differing snuff-back characteristics.

Setting the Amount of

Setup

Snuff-back

NOTE: For Models 255179 and 255181 only

The MD2 valves with hard seats use two snuff-back restrictor rings (13) to set the amount of snuff-back. These two rings are trapped between the main valve body and the nose piece. When the fluid valve pulls back to close, it enters the restrictions, stops flow, and pulls the fluid back until the needle reaches its carbide seat.

Maximum snuff-back results when both restrictors are used. Some snuff-back is still achieved without the restrictors because of the pull-back action of the needles.

When dispensing wide mix ratios, it is best to use a snuff-back restrictor only on the high volume side. This keeps the high volume side from being pulled back into the low volume side.

The MD2 valves with soft seats have an adjustable snuff-back. Turn the knob on the back of the soft seat MD2 valve to adjust the amount of snuff-back.

In general, use only as much snuff-back as necessary to give a good cut-off of flow. Too much snuff-back pulls an air bubble into the mixer. This can cause a drip, or cause the mixer to spit when the valve is re-opened.

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