Group 31 Compact Rotary Actuators

The compact, in-line design of the Group 31 compact rotary actuator consists of an output section containing the drive train and motor, and a control module section housing the electronics. Together, these two sections provide an enclosure designed to meet NEMA 4 specifications for protection against corrosion, dust, and moisture.

The Group 31 incorporates the same type of motor used in Beck’s Group 11 and Group 14 drives. It provides millisecond response to signal commands in a modulating control loop.

General Specification

Output Torque and Timing

Model #	Torque nm (lb-ft)	Stroke Time (sec./90°)(50 Hz)
31-M50, 31-350, 31-250	41 (30)	29
31-M30, 31-330, 31-230	20 (15)	22

Specifications common to all models:

Drive Power	20 Vac, single-phase, 50 or 60 Hz, 0.5A, 60 Watts
Operating Conditions	–40° to 65° C. (–40° to 150° F.) 0 to 99% relative humidity
Action on Loss of Power	Stays in place.
Handwheel	Provides manual operation without electrical power. Non-rotating during automatic operation, does not require declutching mechanism.
Motor	120 V ac, single-phase, no burnout, noncoasting. Capable of 60 starts per minute.
Gear Train	Precision cut, heat-treated alloy steel and ductile iron. Self-locking and self-releasing, able to hold position at 150% rated torque.
Mechanical Stops	Prevent overtravel during automatic or manual operation. Mechanical stops are external to the drive.
Drive Net Weight	25 lbs.
Max. Overhung Load	500 lbs

Switches

Cam controlled, field adjustable. Two limit switches (S3 & S4) open the motor circuit at end-of travel limits. Two auxiliary switches (S1 & S2) provied external signaling as specified through connections made at the terminal board. All four switches are SPDT and are rated for 1 amp at 120 V ac.

Enclosure

Precision machined aluminum alloy castings, painted with corrosion resistant polyurethane paint. All units meet NEMA 4 specifications and are also available FM approved for use in CLass 1, Div. 1, Group D; Class II, Div. 1, Groups E, F, & G; and Class III, Div.'s 1 & 2 hazardous locations.

Specifications for Control Option 3 drives (Models 31-M50 and 31-M30):

Demand Input Signal Range	4–20 mA OR 1–5 V dc
Signal Span Adjust	50% to 125% of 4 V span
Signal Zero Adjust	Up to 120% of span Split Signal Range: 4-12 mA or 12-20 mA
Deadband	1% of span
Sensitivity	0.2% of span
Feedback Signal *	4–20 mA OR 1–5 V dc
Output Stability for Temperature Change	+/- 0.03%/°C of Span for -40°C to 50°C
Stall Relay Contacts	Form A, 10 volt-amps at 120 V ac or dc
Action on Loss of Input Signal (Power On)	Stays in place or runs to any preset position (configurable).
Action on Stall	Relay contacts open after 68 seconds of stall, remote signal available. Power to motor is turned off.
Handswitch	Permits local operation, independent of controller signal. The handswitch is located beneath the control module cover on the control board.

Specifications for Control Option 2 drives (Models 31-350 and 31-330):

Feedback Signal *	4–20 mA OR 1–5 V dc
Output Stability for Temperature Change	+/- 0.03%/°C of Span for -40°C to 50°C

* Feedback may be configured as a two wire transmitter or as a four wire active signal source. Two wire systems require a customer supplied external power supply. Four wire systems require 120 V ac supply to the drive.

Mechanical Features

Motor and Drive Train:

Beck’s Group 31 compact rotary actuators incorporate an exclusive no burnout motor, so that on-line dependability of valves is ensured. Heat-treated alloy steel and ductile iron hypocycloidal gearing transmits torque smoothly and powerfully to the output shaft. The Beck-built control motor provides millisecond response to signal commands in a modulating control loop—eliminating the coasting and overshooting problems typical of outdated electric actuators.

The motor stator of the Group 31 drive is molded into the centerpiece, providing stable delivery of torque without overheating and without burning out.

Mechanical Stops:
Protection from Overtravel Damage

Rugged mechanical stops are furnished as a standard component of the valve mounting assembly. These stops prevent over-travel damage to valves and limit drive travel during manual cycling to maintain proper orientation of the drive output shaft with respect to switches and controls. A built-in position indicator shows the valve position.

Manual Handwheel for Convenient Local Operation:

A manual Handwheel is standard on all Group 31 models for use during installation and testing, or during power outages. This Handwheel does not require a declutch mechanism for operation and does not rotate during automatic operation.

Electrical Features

Limit & Auxiliary Switches

Group 31 compact rotary actuator control modules include four cam-operated switches. Two switches open the motor circuit and function as end-of-travel limit switches, and two auxiliary switches are for external signaling as required by the user. The switch cams are driven directly by the drive’s output shaft for accurate control.

Electric Handswitch:

Convenient Local Operation - Included in the Analog Modulating models is an integral electric Handswitch, which permits safe, local operation at the valve’s individual location. This feature saves time during installation and allows adjustments to be made quickly and easily.

Large Terminal Block for Easy Field Wiring:

The upper board on the Group 31 drive provides wiring terminals for field connection. This board is easily accessible to minimize time needed for installation wiring and testing.

Holds Position Upon Loss of AC Power:

All Group 31 drives stay in place on loss of AC power, with a minimum holding capacity of 150% of rated drive torque. When power is restored, the drive automatically responds to control signal input to move to the position specified.

We are available to help with this product selection, including on-site application reviews, or hands-on demonstrations. If you have any questions about this product please contact us.