Setting the Torque for a Spring Loaded Coupling: A Real-Life Experience

A few years ago, my manager approached me with an interesting challenge when I was working in calibration and testing. Some customers had spring-loaded couplings and wanted to adjust their torque settings. My manager handed me some documents to study and prepare for the task.

The situation was as follows:

• Customer’s Coupling Specification: A coupling with a torque capacity of 10,000 Nm, designed to disengage when the set torque is reached.

• Customer’s Requirement: Adjust the coupling to disengage at 3,000 Nm instead of the maximum 10,000 Nm.

Here’s the step-by-step procedure I followed to meet this requirement:

Setup and Equipment

We used our 20,000 Nm torque calibration test bench, which consisted of:

• A lever arm on the right side, fixed with locking screws to prevent vertical movement.

• A worm gearbox and motor assembly on the left side for torque application.

• Flange couplings in the center for mounting sensors or devices under test.

For the calibration, we mounted the customer’s coupling in series with a 10,000 Nm torque sensor using appropriate adapters.

Calibration Procedure

1. Initial Setup: The customer’s coupling was securely fixed between the test bench couplings and the torque sensor. The lever arm was locked in position using locking screws to prevent any movement during the test.

2. Torque Application: Using the gear box and motor assembly, we started applying torque to the coupling. The torque readings were monitored on the torque sensor display.

3. Observation: When the torque reached approximately 9,980 Nm, the coupling disengaged as designed.

4. Adjusting the Torque: To lower the disengagement torque, we adjusted the screws controlling the coupling’s internal springs, reducing the spring tension incrementally. After each adjustment, we restarted the procedure, applying torque and observing the point at which the coupling disengaged.

5. Fine-Tuning: Through multiple trials, we gradually adjusted the spring tension until the coupling disengaged precisely at 3,000 Nm.

Final Validation

Once the desired torque was achieved, we conducted 10 trials in the presence of the customer to confirm consistency. Each time, the coupling disengaged exactly at 3,000 Nm, meeting their requirements perfectly.

Outcome

The customer, initially skeptical about whether we could achieve the required adjustment, was thoroughly impressed with our methodical approach and the successful results. Their satisfaction and appreciation were a rewarding conclusion to this challenging task.