Several details that are easily overlooked in valve torque testing
Having worked in valve testing for many years, I've found that while torque testing seems like a routine procedure, there are many details that are easily overlooked in practice. Properly handling these details can significantly improve the reliability of the test results.
Detail 1: Status confirmation before testing
Many testing errors are not actually caused by the equipment, but by the valve status not being clearly confirmed before the test.
Is the valve in a normal installation condition?
Are there any residual media or impurities on the sealing surface?
Is the connection between the actuator and the valve stem aligned?
If these issues are not confirmed, the measured torque data may be significantly inaccurate. For example, if the connection is misaligned, the measured torque will be too high, even though the valve itself is not actually faulty.
Detail 2: The impact of testing speed
Different types of valves have varying sensitivities to testing speed. In particular, for large-diameter valves or those with special sealing structures, the measured torque tends to be too high if the testing speed is too fast.
In practice, it is recommended to run the test once at a lower speed first to observe the trend of the torque curve, and then adjust the test speed according to the actual situation. Many devices support speed settings, but this is easily overlooked, and it is unreasonable to use the same set of parameters to test all valves by default.
Detail 3: Completeness of data records
Previously, when recording data manually, only a single final torque value was typically recorded. However, when analyzing valve malfunctions, looking at just one value is often insufficient.
Some testing equipment can now automatically record torque-angle curves, which is invaluable information. For example, a sudden jump in the torque curve may indicate foreign objects or damage to the sealing surface; an overall high curve may indicate overly tight assembly or insufficient lubrication. Without curve data, these anomalies are difficult to locate.
Therefore, when selecting testing equipment, data acquisition and storage functions are more practical than simply pursuing high precision.
Detail 4: Regular calibration and comparison
Sensors will drift over time, which is normal. If they are not calibrated regularly, the accumulated errors will affect their judgment.
My approach is:
The standard torque sensor is sent for testing every six months.
In daily use, periodically compare the values on-site using standard weights or a torque wrench.
Keep records of each calibration for easy traceability.
In addition, comparisons between different devices are also meaningful. If conditions permit, the same valve can be tested on different devices to see if the results are consistent. This cross-validation can uncover potential problems with individual devices.
A suggestion regarding model selection
If your industry peers are considering acquiring torque testing equipment, in addition to focusing on the measurement range and accuracy, I think the following points are also worth careful evaluation:
Speed control range: Can it meet the testing requirements of different types of valves?
Data sampling frequency: Can it capture instantaneous changes in torque?
Software Functions: How convenient are data export, curve analysis, and report generation?
After-sales response: Can technical support be obtained promptly when a malfunction occurs?
While price is important, the long-term stability of the equipment and the timeliness of after-sales service have a greater impact on daily work.
summary
Valve torque testing may seem simple, but to achieve accurate and comprehensive measurements, there are still many details to pay attention to. From pre-test preparation, speed selection, data recording to regular calibration, each step will affect the final result.
The above are some experiences I've accumulated in my practical work, which I hope will be helpful to my colleagues. I also welcome everyone to exchange ideas and share typical cases and solutions encountered.
