Asco 8551 Series Installation & Maintenance Instructions

Service Notice

Except for coil replacement, the Series 8551 are not repairable.
When any performance problems are detected during routine
inspection, replace valve immediately.
For catalog numbers prefixed WT or EF, see separate solenoid
Installation and maintenance instructions for information on:
Wiring, Solenoid Temperature, Cause of Improper Operation
and Coil Replacement.

DESCRIPTION

Series 8551 valves are 3-way or 4-way, 5 ported 2 position
piloted spool type single or dual solenoid valves designed for air
or inert gas service. Valves are made of rugged anodized
aluminum. A built-in manual operator allows manual
operation when desired or during an electrical power outage.
Each valve may be used for 3-way (normally closed) or 4-way
operation by using the appropriate flow plate provided. Flow
plates are marked (3/2) for 3 Ports, 2 Positions (3-way
operation) or (5/2) for 5 Ports, 2 Positions (4-way operation).
These valves are supplied with all necessary hardware for a
NAMUR direct mount installation i.e. flow plates, gaskets,
mounting screws and a locating set screw. See Flow Selection
And Mounting section.
Valves catalog numbers prefixed SC are supplied with an
open-frame spade plug connection coil (3x DIN 46244). A
DIN Plug Connector Kit No. K226061-001, is available from
ASCO.

APPLICATIONS

Typically, the 3-way (3/2) normally closed mode is used for a
single acting (spring return) actuator; 4-way (5/2) mode for a
double acting actuator.
solenoid spool­
valve control
adapted for

3/2 operation

Port Markings: 1 = Pressure,
3 & 5 = Exhaust
©
solenoid spool­
valve control
adapted for
5/2 operation
Solenoid
Pilot
Valve
Quarter
Turn
Actuator
Process
Valve
2 & 4 = Cylinder
MM All Rights Reserved.
IMPORTANT: Minimum operating pressure differential 30 psi;
maximum 150 psi.
Breather Function 3-way (3/2) mode only: Allows for spring side
of a spring return actuator to vent at all times through valve
exhaust port 3.
Single Solenoid:
automatic return of the valve on electrical power failure or loss
of main line pressure is required.

3-Way NC Single Solenoid Operation

Solenoid De-energized: Flow is from port 2 to port 3. Port 4
is open to exhaust port 3 (breather function); pressure port 1 is
closed Slight pilot exhaust is also apparent. Port 5 is not used.
Solenoid Energized: Flow is from pressure port 1 to port 2. Port
4 is open to exhaust port 3 (breather function); pilot exhaust is
closed.
3-Way Single Solenoid (3/2)
Solenoid De-energized
2
Pilot
Exh.
3 1

4-Way Single Solenoid Operation

Solenoid De-energized: Flow is from pressure port 1 to port
4 and from port 2 to port 3. Port 5 is closed. Slight pilot exhaust
is also apparent.
Solenoid Energized: Flow is from pressure port 1 to port 2 and
from port 4 to port 5. Port 3 and pilot exhaust are closed.
4-Way Single Solenoid (5/2)
Solenoid De-energized
2 4
Pilot
Exh.
3 1 5
Dual Solenoids: Solenoid may be energized momentarily or
continuously depending upon application. Dual solenoid
valves are used where equipment must not change position
when electrical power fails. Valve operates when one solenoid
is energized and returns when the other solenoid is energized.
Printed in U.S.A.
50-60 Hanover Road, Florham Park, New Jersey 07932 www.ascovalve.com
OPERATION
This type of operation is used where
Solenoid Energized
2
4
Pilot
Exh.
3
5
Solenoid Energized
2
Pilot
Exh.
3 1 5
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