I would like to ask about the methods for adjusting the travel of control valves
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I would like to ask everyone: when maintaining a pneumatic control valve and the clamp on the valve stem is removed, how can one determine the correct position of that clamp in order to maintain the valve’s original operating range? Is the method for determining the clamp position the same for air-operated open valves and air-operated closed valves? Also, what does spring preload mean in simple terms, and how can it be adjusted? What should it be adjusted to? Thank you very much:handshake:handshake
Come and learn* drop~ It sticks well! Thank you, OP!
The travel of the valve and the connection of the valve stem are not theoretically related to each other; the stroke of the valve stem is determined by adjusting the spring preload, with the valve core disconnected from it. The process of connecting the valve stem is essentially one in which the starting position of the valve core’s movement coincides with the starting position of the actuator’s stroke. The basic principle for determining the position of the clamping plate is the same for air-open valves and air-close valves; however, there are differences in the approach used for specific valves. Place the valve core in the fully closed position (for example, for a normally open valve, press it all the way down; for a normally closed valve, raise it to the highest position). Put the actuator in a position that corresponds to a full-close signal (for example, apply a 20 KPa signal to a pneumatically operated open valve, and a 100 KPa signal to a pneumatically operated closed valve), and then lock the two together. Check the itinerary and valve closing positions again.
First, place the valve core in the closed position; for air-operated valves, apply a signal of 0.2 MPa and use the fixing clamps； For the air shut-off valve, a signal of 1.0 MPa is applied, followed by fixing the clamping plate; after the plate is secured, accuracy verification is carried out.
It’s actually quite simple, but it’s not ideal. Whether the valve is open or closed, the actuator should be at half its travel distance; the clamping plate and the positioner need to be fixed at a 90-degree angle, parallel to each other. Then the positioner needs to be adjusted again. This shouldn’t be too much of a problem. There are two solutions: 1. Re-clip the clamping plate in its original position; 2. Clip it in any position as long as it doesn’t cause scraping during full travel, and then adjust the positioner again. The last option involves bearing the shipping costs to send it back to the manufacturer for them to fix it… haha···
The spring preload is the lower limit of the air pressure value indicated on the nameplate! Adjusting to the lower air pressure limit through the pressure valve is the spring preload