EFD 781S MAINTENANCE GUIDE

IMPORTANT!

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781S Series Dispense Valve

MAINTENANCE & PARTS GUIDE

Electronic pdf files of EFD®manuals are also available at
www.efd-inc.com/manuals.html.

For EFD sales and service in over 30 countries,
contact EFD or go to www.efd-inc.com/contact

EFD, Inc.

East Providence, RI USA
800-556-3484; [phone] (outside the USA)
[e-mail] www.efd-inc.com

EFD International Inc.

Dunstable, Bedfordshire, UK
0800 585733 or [phone]
Ireland 00800 8272 9444
[e-mail] www.efd-inc.com

EFD, Inc., Asia

China: [phone]
[e-mail] www.efd-inc.com/cn
Singapore: [phone] [e-mail]

®

A NORDSON COMPANY

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Valve maintenance

To thoroughly clean the fluid body and
replace needle packings:

1. Remove needle stroke control knob
and spring.

2. Remove air cap retainer, then air
cap, nozzle and fittings.

3. Remove fluid body from air cylinder
body using a .11” hex wrench, then
remove O-ring.

4. Clean fluid body, air cap and nozzle
in appropriate solvent.

5. Use extraction tool #7803
to remove needle packings
from fluid body.

6. Remove any remaining pack-

ings and spring from needle.

Note: Before reassembling,
clean fluid body, air cap and
nozzle in appropriate solvent and
replace O-ring. Clean needle with
cloth dampened in solvent.

Reassemble the valve in reverse
order of disassembly. Ensure that
the small O-ring and washer on
the bottom of the air cylinder body
are back in place before reinstalling
the packing spring. Lubricate parts
indicated with Nye Lubricant #865
included in the Maintenance Kit.

Valve Disassembly and
Reassembly Procedures

CAUTION: To prevent damage, the valve
must be disassembled starting at the fluid
outlet end of the valve.

www.efd-inc.com [e-mail] USA 800-556-3484 Europe [phone] Asia [phone]

Sales and service of EFD dispensing systems are available worldwide.

Nozzle air
cap retainer
#7819SS
(stainless steel)

Nozzle

(Viton)
#7825

Fluid inlet fitting
#7543BP - for .25" OD tube
#7610BP - for .375" OD tube

Screws
H6-32X3/8SHC

O-ring

Needle
packing
assembly
#7810

Air cylinder body
#7879-SS
(stainless steel)
#7879
(hard-coated aluminum)

Packing
spring
#7808

Nozzle/air cap
Round Fan
#7857-46SS #7857F-46SS
#7857-28SS #7857F-28SS
#7857-14SS #7857F-14SS

#7857-46WA-SS #7857-46WF-SS

O-ring
(Buna-N)
#4049

Fluid body
#7878-SS (stainless steel)
#7878 (hard-coated aluminum)

Retaining
washer #7807

O-ring (Buna-N)

#7806

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B

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Maintenance Kit

#781S-RK

Includes all air cylinder and
fluid body O-rings, needle
packings and lubricant.

Tools required:

6” adjustable wrench
1/8” hex wrench

7/64” hex wrench
.035 hex wrench
snap-ring pliers
packing extraction tool (#7803)

Replacing piston and needle
assembly or piston O-ring

7. Remove needle stroke control
knob.

8. Remove piston return spring
and thrust washers.

9. Remove the snap ring.

10. With small pliers on the spring
pilot, pull the piston and nee­dle assembly out of air cylin­der. The piston and needle
assembly is one unit and
cannot be disassembled.

11. Clean the air cylinder body
wall, replace piston O-ring and
apply lubricant.

Reassemble the valve in reverse
order of disassembly. Lubricate

parts indicated with Nye Lubricant
#865 included in the Maintenance
Kit.

Reseating the needle and nozzle
assembly

12. Rotate the stroke adjustment knob
clockwise to the closed position.

13. To compress the needle into the
nozzle, further rotate the stroke
adjustment clockwise one addi­tional reference mark.

14. Return stroke adjustment to normal
setting and cycle the valve. If a
slight leak remains, repeat steps 1
and 2.

15. If the leak persists, replace the
nozzle.

www.efd-inc.com [e-mail] USA 800-556-3484 Europe [phone] Asia [phone]

Sales and service of EFD dispensing systems are available worldwide.

Snap ring
#7526

Piston and needle
assembly #7805-SS
includes O-ring (Buna-N)

O-ring (Buna-N)
#7519

Needle stroke reference control
#7432-SS (stainless steel)
#7432 (aluminum)

Thrust
washers
#7809

Air hose assembly
#7830

O-ring (Buna-N)

Piston return spring
#7802

#7517

Troubleshooting Guide

Fluid flows from the nozzle but
will not spray

• Nozzle air pressure may be too
low. Increase air pressure.

• The air passageway between the
nozzle and air cyclinder cap may be
obstructed.

Remove the air

cyclinder

cap, and clean the air

cyclinder

cap and nozzle.

• If the fluid viscosity is too high, it
will not atomize. Reduce viscosity.

No fluid flow

• If valve operating air pressure is
too low, the valve will not open.
Increase air pressure to 70 psi
(4.8 bar) minimum.

• The reservoir air pressure may
not be high enough. Increase
pressure.

• The nozzle may be clogged.
Clean the nozzle.

• The stroke adjustment may be
closed. Open stroke adjustment.

• The control and nozzle air lines
may be reversed. Check for
proper connection.

Valve does not provide clean
shut-off, leaving build-up on
the nozzle

• The needle may be improperly
seated in the nozzle seat. Remove
the nozzle, clean the needle and
nozzle, replace worn or damaged
parts.

• Needle packings may be binding
due to leakage, preventing the nee­dle from fully closing. Disassemble
the valve and replace the packings
if there is evidence of leakage.

USA: 800-556-3484 or [phone]
Europe: 0800 585733 or [phone]
Asia: [phone]
[e-mail] www.efd-inc.com

©2006 Nordson Corporation 781S-MAINT-01 v062606

A NORDSON COMPANY