Linear Pneumatic Actuator Sizing

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PNEUMATIC ACTUATOR SIZING

To use the Actuator Sizing Table below, the following information is required:

  1. Required maximum valve (load) thrust in pounds (T)

  2. Required valve (load) stroke in inches. (S)

  3. Minimum air (oil pressure for hydraulic actuator) supply pressure in psi. (P).

  4. For spring return actuator, the thrust value should be multiplied by approximately 2.8 to 3.0 times before using the table below.  This is because, apart from providing the required valve thrust, the air supply should furnish sufficient force to overcome the initial spring-preload force and the force to compress the spring. Thus, a spring return actuator will have a bore approximately 70% larger than its double acting equivalent.  Because of the variation of available thrust values during the actuator stroke, it is possible to optimize the spring size based on the specific load profile required.  Consult kanair for details.

The valve thrust and stroke can be obtained from the valve manufacturer. If the actuator is retrofitted on an existing valve, these values can be measured and/or estimated reasonable accuracy by knowing the valve parameters, valve size and the differential pressure across the valve.  Consult Kanair for details.

LINEAR PNEUMATIC ACTUATOR SIZING

MODEL NO.

BORE (inch)

ACTUATOR THRUST FOR VARIOUS PRESSURES

AIR SUPPLY PRESSURE IN psi

40

60 80 100 120

PL 2.5 x * - DA

2.5

184

276

368

460

552

PL 3.25 x * - DA

3.25

300

451

601

751

901

PL 4 x * - DA

4

471

707

942

1,178

1,414

PL 5 x * - DA

5

754

1,131

1,508

1,885

2,262

PL 6 x * - DA

6

1,072

1,607

2,143

2,679

3,215

PL 8 x * - DA

8

1,951

2,927

3,902

4,878

5,854

PL 10 x * - DA

10

3,045

4,568

6,091

7,613

9,136

PL 12 x * - DA

12

4,398

6,597

8,796

10,996

13,195

PL 14 x * - DA

14

5,961

8,942

11,922

14,903

17,884

PL 16 x * - DA

16

7,846

11,769

15,692

19,615

23,538

PL 18 x * - DA

18

9,982

14,974

19,965

24,956

29,947

PL 20 x * - DA

20

12,284

18,425

24,567

30,709

36,851

PL 22 x * - DA

22

14,923

22,384

29,845

37,307

44,768

* above denotes the valve stroke (minimum cylinder stroke required)

Example: Double Acting Actuator

Required Valve Thrust , T............................... = 3,500 lbs.
Safety Factor Used....................................... = 25%
Thrust Value for Actuator Sizing (1,25 x 3500).... = 4,375 lbs.
Minimum Air Pressure Available.......................... = 80 psig
From Table I, Cylinder Bore Required.................. = 10" ( 10" bore actuator provides 6,091 lbs thrust at 80 psig
Valve Stroke Required (say, for 6" gate valve).... = 7.5"
ACTUATOR MODEL SELECTED..................... = PL 10 x 08-DA

Example: Spring Return  (say, Spring to Close) actuator

Required Valve Thrust , T (say)........................ = 3,500 lbs.
Safety Factor Used........................................ = 25%
Thrust Value for Actuator Sizing (1,25 x 3500).... = 4,375 lbs.
Thrust for Sizing Spring Cylinder =(3 x 4375) = 13125 lbs.
Minimum Air Pressure Available.......................... = 80 psig
From Table I, Cylinder Bore Required................. = 16" ( 16" bore actuator provides 15,692 lbs thrust at 80 psig
Valve Stroke Required (say, for 6" gate valve)..... = 7.5"
SPRING RETURN ACTUATOR MODEL SELECTED..... = PL 16 x 08-SRC
Note: Spring return actuator can be optimized by adjusting the spring rate or by evaluating the required thrust as a function of valve stroke.  Consult Kanair for more details.

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