72 SERIES TWO STAGE SERVOVALVES

72 Series

Servovalves

72 SERIES

TWO STAGE SERVOVALVES

 

 

 

 

 

 

72 SERIES SERVOVALVES

 

The 72 Series flow control servovalves are throttle valves for 3 and preferably 4-way applications.They are a high performance, two-stage design that covers the range of rated flows from 25 to 60 gpm at 1000 psi valve drop.The output stage is a closed center, four-way sliding spool.The pilot stage is a symmetrical double-nozzle and flapper, driven by a double air gap, dry torque motor. Mechanical feedback of spool position is provided by a cantilever spring.The valve design is simple and rugged for dependable, long life operation.

 

These valves are suitable for electrohydraulic position, speed, pressure or force con-trol systems with high dynamic response requirements.

 

Principle of operation

 

An electrical command signal (flow rate set point) is applied to the torque motor coils, and creates a magnetic force which acts on the ends of the pilot stage armature.This causes a deflection of armature/flapper assembly within the flexure tube. Deflection of the flapper restricts fluid flow through one nozzle which is carried through to one spool end, displacing the spool.

 

Movement of the spool opens the supply pressure port (P) to one control port, while simul-taneously opening the tank port (T) to the other control port.The spool motion also applies a force to the cantilever spring, creating a restoring torque on the armature/flapper assembly. Once the restoring torque becomes equal to the torque from the magnetic forces, the armature/flapper assembly moves back to the neutral position, and the spool is held open in a state of equi-librium until the command sig-nal changes to a new level.

 

In summary, the spool position is proportional to the input current and with constant pressure drop across the valve, flow to the load is proportional to the spool position.

 

VALVE FEATURES
2-stage design with dry torque motor	Rugged, long-life design
Low friction double nozzle pilot stage	High resolution, low hysteresis
High spool control forces	Completely set-up at the factory
High dynamics	Optional fifth port for separate pilot supply
Field replaceable pilot stage filter

 

The actual flow is dependent upon electrical command signal and valve pressure drop.The flow for a given valve pressure drop can be calculated using the square root function for sharp edge orifices:

 

Q [gpm] = calculated flow

 

QN [gpm] = rated flow

 

∆ p [psi] = actual valve pressure drop

 

∆ pN [psi] = rated valve pressure drop

 

 

This catalog is for users with technical knowledge.To ensure that all necessary characteristics for function and safety of the system are given, the user has to check the suitability of the products described here. In case of doubt, please contact Moog Inc.

 

 

72 SERIES

GENERAL TECHNICAL DATA

 

Operating Pressure	up to 3,000 psi*
ports P, X,A and B
port T	up to 3,000 psi
Temperature Range
Fluid	-40°F to 275°F
Ambient	-40°F to 275°F
Seal Material	Viton **
Operating Fluid	Compatible with common
	hydraulic fluids, other fluids
	on request.
Recommended viscosity	60-450 SUS @ 100°F

System Filtration: High pressure filter (without bypass, but with dirt alarm) mounted in the main flow and if possible, directly upstream of the valve.

Class of Cleanliness: The cleanliness of the hydraulic fluid greatly effects the performance (spool positioning, high resolution) and wear (metering edges, pressure gain, leakage) of the servovalve.

Recommended Cleanliness Class
For normal operation	ISO 4406 < 14/11
For longer life	ISO 4406 < 13/10
Filter Rating recommended		≥
For normal operation	ß10		75 (10 µm absolute)
For longer life	ß5	≥	75 (5 µm absolute)
Installation Operations	Any position, fixed or moveable.
Vibration	30 g, 3 axes
Weight	7.75 lb. (3.52 kg)
Shipping Plate	Delivered with an oil sealed
	shipping plate.

 

• Maximum special order is 5,000 psi

 

• Other seal material upon request

 

 

 

 

 

 

72 SERIES

TECHNICAL DATA

 

 

 

Model . . .Type				72 . . . . .
Mounting Pattern				ISO 10372 - 06 - 05 - 0 -92
Valve Body Version				4-way
			2-stage with spool-bushing assembly
Pilot Stage				Nozzle/Flapper, High flow
Pilot Connection	Optional Internal or External
Rated Flow	(± 10%) at ∆ pN   = 1,000 psi	[gpm]	25	40	60
Response Time*		[ms]	16	26	40
Threshold*		[%]		< 1.5%
Hysteresis*		[%]		< 4.0%
Null Shift	at ∆ T = 100°F	[%]		< 4.0%
Null Leakage Flow*	max.	[gpm]		0.55 to 1.30

* Measured at 1,000 psi pilot or operating pressure

 

 

 

Step Response

 

 

Typical characteristic curves

with ±40% and ±100% input signal, measured at 3,000 pilot or operating pressure.

 

 

Stand ard Valves

 

72 SERIES

INSTALLATION DRAWINGS

 

TYPICAL SUBPLATE MANIFOLD

 

Null Adjust: Flow out of Control Port B will increase with clockwise rotation of null adjust screw (3/32 hex key).

 

The mounting manifold must conform to ISO 10372-06-05-0-92.

Surface to which valve is mounted requires a √³² [∆∆ ] finish, flat within 0.002[0.05] TIR.

 

Standard electrical connector mates with MS3106F14S-2S or equivalent.

 

 

Note: Before applying electrical signals, the pilot stage has to be pressurized.

 

Procedure to Configure a 72 Series Servovalve for External Pilot Operation

 

1. Remove the set screw from the “X” port on the base of the valve using a 1/8'' Allen wrench.

 

2. Thread a #2-56 screw into the o-ring plug that is now visible and remove it from the “X” port.

 

3. Remove the four (4) socket head cap screws and lockwashers that retain the cover plate for the field replaceable filter, using a 3/16'' Allen wrench.

 

4. Use one of the screws to pull the filter and filter housing out of the filter cavity of the body. The filter housing has two (2) o-rings on its O.D.The housing will come part way out, then stop after the second o-ring passes the internal relief in the body. At this time it may be easier to remove the visible o-ring and carefully pry the housing and filter out with two opposing flat blade screw drivers, than to continue pulling on the screw. Be careful not to damage the o-ring groove.

 

5. A bore will be visible inside the body cavity where the o-ring plug must be inserted.

 

6. Retain the o-ring plug with the set screw.

 

7. Re-install the filter and filter housing in the cavity.

 

8. Re-install the filter cover, retaining screws and lockwashers.Torque the screws to 85 in-lbs.

 

 

 

72 SERIES

ORDERING INFORMATION

SPARE PARTS AND ACCESSORIES

 

 

Preferred configurations highlighted.

All combinations may not be available.

Options may increase price and delivery.

Technical changes are reserved.

 

• Optional designs are available with intrinsically safe coils (FM, CSA and ATEX approved), and/or special spool bushing lap configuration.
• Available seal materials: VITON (Std.), BUNA or EPR.

 

SPARE PARTS AND ACCESSORIES

O-Rings (included in delivery),	FPM 85 Shore	Moog P/N
for P,T, A and B	ID 0.801 x 0.070	42082-040
for X	ID 0.364 x 0.070	42082-013
Mating Connector, waterproof IP 65 (not included in delivery)		49054F014S002S (MS3106F14S-2S)
Flushing Block		G4321AM001
Mounting Bolts (not included in delivery)
3/8 - 16 NC x 2 long (4 pieces)		A31324-332B
Replaceable Filter Cartridge		22050K002
Field Replaceable Filter Kit		B52555RK099K001