Torque Requirements for Parker Pneumatic Rotary Actuators

Design Torque

Design torque represents the maximum torque than an actuator must supply in an application. This maximum is the greater of the Demand Torque or the Cushion Torque. If the demand torque exceeds what the actuator can supply, the actuator will either move too slowly or stall. If the cushion torque is too high, the actuator may be damaged by excessive pressure. Demand torque and cushion torque are defined below in terms of load, friction and acceleration torque, along with equations for calculating demand torque and cushion torque for some general applications.

T - Torque

The amount of turning effort extered by a rotary actuator.

TD - Demand Torque

The torque required from the actuator to do the job - the sum of the load torque, friction torque and acceleration torque, multiplied by an appropriate design factor. Design factors vary with the applications and the designers' knowledge.

TD = Tα  + Tf + TL

TL - Load Torque

The torque required to equal the weight or force of the load. The load torque term is intended to encompass all torque components that aren't included in the friction or acceleration terms.

Tf - Friction Torque

The torque required to overcome friction between any moving parts, especially bearing surfaces.

Tf = μWr

Tα - Acceleration Torque

The torque required to overcome the inertia of the load in order to provide a required acceleration or deceleration. See the Rotary Actuators Basic Equations page for more information regarding mass moments of inertia and equations for determining acceleration (α).

Tα = Iα

TC - Cushion Torque

The torque that the actuator must apply to provide a required deceleration. This torque is generated by restricting the flow out of the actuator (meter-out) to create a back pressure which decelerates the load. This back pressure/deceleration often must overcome both the inertia of the load and the driving pressure (system pressure) from the pump.

TC = Tα + PrV/θ - Tf ± TL

The friction torque Tf reduces the torque the actuator must apply to stop the load. The load torque TL may add to, or subtract from the torque required from the actuator, depending upon the orientation of the load torque. For example, a weight being swung upward would result in a load torque that is subtracted.

WARNING: Rapid deceleration can cause high pressure intensification at the outlet of the actuator. Always insure that cushion pressure does not exceed the manufacturer's pressure rating for the actuator.

KE - Kinetic Energy (1/2 Jmω2)

The amount of energy that a rotating load has. The rotator must be able to stop the load. All products have kinetic energy rating tables. Choose the appropriate deceleration option (i.e., bumper, cushions, shock absorbers, etc.) that meets or exceeds the kinetic energy of the load.

Demand Torque Examples

Example 1:

TD = Tα  + Tf + TL

Tα = 0

Tf = 0

TL = (500 lb)(10 in) = 5,000 lb-in

TD = 5,000 lb-in

 Demand Torque Example 1

Example 2:

(The 500 lb rotating index table is supported by bearings with a coefficient of friction of 0.25. The table's acceleration is at 2 rad/sec2. The table's mass moment of inertia is 2,330 lb-in-sec2.)

TD = Tα  + Tf + TL

Tα = Iα = (2,330 lbs-in-sec2)(2/sec2) = 4,660 lb-in

Tf = μWrb = 0.25 (500 lb)(55 in) = 6,880 lb-in

TL = 0

TD = 4,660 lb-in + 6,880 lb-in = 11,540 lb-in

demand-torque-example-2.png

Example 3:

TD = Tα  + Tf + TL

Tα = 0

Tf = 0

TL = (500 lb)(10 in) = 5,000 lb-in

TD = 5,000 lb-in

 demand-torque-example-3.png

Torque Selection Chart

Parker rotary actuators provide output torque up to 10,000 lb-in. The chart below shows the nominal torque output range of various actuator models at 100 psi.

Caution: This chart is intended as a guide only. Refer to actual product data pages before specifying an actuator. Factors such as pressure rating, rotation and actual torque output may be affected by specific product details and options.

Nominal Torque at 100 PSI

Output Torque (lb-in) Rotation < 95° Rotation > 100°
Vane Models Rack & Pinion Models Vane Models Rack & Pinion Models
10000   HP10   HP10
9000        
8000        
7000        
6000        
5000   HP4.5   HP4.5
4000        
3500        
3000 PRN800D B6714   B6714
2500   PTR322   PTR322
2000 PV46D      
1500 PRN800S   PRN800S  
1250 PV44D PTR321, B6713   PTR321, B6713
1000        
900 PRN300D PTR252 PV46 PTR252
800        
700 PV36D, PV42D      
600   PTR202, B6712 PV44 PTR202, B6712
500 PV42D, PRN150D PTR251   PTR251
400 PV33D, PRN300S   PV36, PRN300S  
300   PTR201 PV42 PTR201
250   PTR152   PTR152
200 PRN150S   PV33, PRN150S  
150 PV22D, PRN50D PTR151, B6711   PTR151, B6711
100 PRN30D      
80   PTR102 PV22 PTR102
60 PRN50S   PRN50S  
40 PRN30S PTR101 PRN30S PTR101
35 PV11D      
30        
25 PRNA20S   PRNA20S  
20 PV10D      
15 PRNA10S   PV11, PRNA10S  
10     PV10  
5 PRNA1S, PRNA3S   PRNA1S, PRNA3S  

 

 

Available Pneumatic Cylinder Styles

Tie-rod air cylinder - non-rotating Tie Rod Cylinders
Round Body Cylinders
Compact Cylinders
Guided Cylinders
Rodless Cylinders

 

Quote by Part Number Help with Cylinder Identification

Engineering & Product Selection Information

Pneumatic Product Selection

  • Pneumatic Actuators & Air Cylinders
  • Pneumatic Cylinders
  • Automation Products: rotary actuators, grippers, slide tables, rotary tables, escapement
  • Actuator Accessories: Linear alignment couplers, flow controls, air oil tanks, rodlocks, electronic sensors, shock absorbers

Application Engineering Data

 


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