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OMAL Spa
CONVERSION DA ? SR

CONVERSION DA ? SR

Product catalog summary

Introduction
This document provides instructions for converting a Double Acting (DA) pneumatic actuator into a Spring Return (SR) actuator. The conversion process is necessary due to the different assembly requirements of DA and SR actuators, particularly in how they generate torque and handle valve positions.

Specifications
DA actuators generate the highest torque in the closed valve position, whereas SR actuators use springs to close the pistons. This fundamental difference necessitates a distinct assembly process for each type.

Safety Precautions
Before beginning any disassembly, ensure there is no pressure in the air supply system. OMAL disclaims responsibility for any damage resulting from improper use or unauthorized modifications.

Conversion Procedure

Step 1: Remove the Caps and Pistons
For smaller actuators, rotate the shaft to disengage the pistons. For larger actuators, apply air pressure (maximum 1 bar) to eject the pistons.
Step 2: Rotate the Scotch Yoke and Invert the Pistons
Rotate the scotch yoke by 90 degrees and turn the pistons upside down by 180 degrees.
Step 3: Reassemble the Pistons
Reinsert the pistons, ensuring the slots are centered. Avoid using tools that could damage the mechanism.
Step 4: Install the SR Caps
Attach the SR caps, which come with pre-loaded springs that should not be altered.

Conclusion
Following these steps will successfully convert a DA actuator into an SR actuator, ensuring proper functionality and torque generation.

Catalog excerpts

n° 8_0083 CONVERSION DA ⇒ SR OMAL S.p.A. Via Ponte Nuovo 11 - 25050 RODENGO SAIANO (BS) ITALY Tel. 030/8900145 r.a. - Fax 030/8900423

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All data and specifications in this manual may be changed at any time and without prior notification to improve our products. They cannot be considered binding.

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CONVERTING A DOUBLE ACTING (DA) ACTUATOR INTO SPRING RETURN (SR) SR ACTUATOR OMAL Double Acting pneumatic actuators differ from Spring Return ones because of the way components are assembled. As the piston slots are approx. 15 degree off the center line, the two extreme positions (completely closed or completely open pistons) yield two different torque values. Specifically actuators are required to generate the highest torque value (i.e. the highest of the two mentioned above) in the “closed valve” position (where the valve gives the highest resistance). In a DA actuator the valve closes when...

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SECOND STEP: ROTATE THE SCOTCH YOKE AND TURN THE PISTONS UPSIDE DOWN Acting on the output shaft, give the scotch yoke a 90° rotation and then turn the pistons upside down by 180°. THIRD STEP: RIASSEMBLING THE PISTONS Put the pistons back in trying to center the slots (the two pistons need to go in at the same time without using any hammer or tool which may damage the actuator mechanism). FORTH STEP: PUT THE SR CAPS ON OMAL SR caps come with springs. The springs pre-loaded at the factory and shall not be removed or altered in any way for any reason. 2 Conversion DA⇒SR 2000 rif. 01 - n° 8_0083...

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