1. Adjusting Screw
Sets the preload of the actuator spring. Controls sensitivity, spring compression, and fail-position behavior.
2. Adjusting Screw Gasket
Seals around the adjusting screw to prevent air leakage.
3. Spring Button
Supports and aligns the top of the spring so compression stays uniform.
4. Cylinder
Main actuator housing that holds compressed air. Air pressure acts on the piston inside.
5. Spring
Provides the opposing force to the piston. Determines fail-open/fail-close action and ensures return travel.
6. Piston
Moves up or down based on air pressure, transferring force to the actuator stem.
7. Piston Retaining Nut
Locks the piston onto the actuator stem, ensuring both move together.
8. Piston O-Ring / Piston Stem O-Ring
Creates an airtight seal around the piston to prevent air leakage between cylinder chambers.
9. Actuator Stem
The shaft connected to the piston. Transfers movement directly to the valve stem and plug.
10. Actuator Stem Spacer
Maintains proper actuator stem height and ensures correct travel alignment.
11. Actuator Stem Bushing & O-Ring
– Bushing: Guides the stem to ensure straight, smooth movement.
– O-Ring: Prevents air leakage along the stem passage.
12. Stem Bellows
Protects the stem from dust, moisture, and contamination.
13. Cylinder Retaining Ring
Holds the cylinder securely to the actuator housing.
14. Stroke Plate
Indicates actuator travel position (e.g., % open). Used for calibration and troubleshooting.
15. Yoke
Structural connector between actuator and valve body. Must withstand all actuator forces.
16. Yoke Clamp / Yoke O-Ring
Provides a sealed and rigid mechanical connection between the actuator and yoke.
17. Stem Clamp
Locks the actuator stem to the valve stem so movement is transferred correctly.
18. Upper Packing / Lower Packing
Soft sealing materials around the valve stem to prevent process fluid from leaking while the stem moves.
19. Packing Spacer
Ensures equal compression on packing layers for consistent sealing performance.
20. Gland Flange
Applies downward force on the packing to create a tight seal.
21. Upper & Lower Stem Guide / Guide Liner
Keep the stem centered and stable, preventing sideways movement.
Essential for accuracy and smooth control valve operation.
22. Bonnet
Covers and protects the stem assembly. Houses the packing and guides.
23. Bonnet Flange & Bolting
Mechanical connection between bonnet and valve body.
24. Bonnet Gasket
Provides sealing between bonnet and body to prevent process leakage.
25. Seat Retainer
Holds the seat ring firmly in position.
26. Seat Ring
The primary sealing surface where the plug closes against to stop flow.
27. Seat Ring Gasket
Seals between the seat ring and valve body to prevent bypass leakage.
28. Plug
The control element of the valve. Moves up/down to regulate flow.
29. Body
Main pressure-containing housing where fluid flows through.