Guide to Bolt Torque Validyne Pressure Transducers and Sensors

A key advantage of Variable Reluctance pressure transducers is their serviceability and flexibility. They can be disassembled to have their pressure range changed by installing a new sensing diaphragm. This process is crucial for adapting to different applications and is a common practice in laboratory and testing environments. However, when changing diaphragms, applying the correct body bolt torque is not just a recommendation—it is extremely critical to the sensor’s performance and accuracy.

An improperly torqued transducer can lead to a host of issues. Under-torquing can result in leaks, which will cause inaccurate readings or a complete failure to hold pressure. More dangerously, over-torquing the bolts can warp the transducer’s body, distort the sensitive diaphragm, and create uneven stress points. This distortion can severely compromise the transducer’s calibration, linearity, and ultimate measurement accuracy, potentially causing permanent damage.

Best Practices for the Torquing Process

The sequence for torquing the body bolts is a precise procedure, very similar to mounting a car wheel. The goal is to ensure even and uniform pressure distribution across the sealing surface. You should always apply the torque in a crisscross pattern and in incremental stages. For example, first snug all bolts finger-tight, then use a torque wrench to bring them all to one-third of the final value, then two-thirds, and finally to the full specified torque. Never fully torque one bolt while the others are loose, as this will almost certainly misalign the housing and damage the diaphragm.

To ensure a perfect seal and optimal performance, always use a calibrated torque wrench. Avoid using simple hex keys or nut drivers, as these make it impossible to apply a measured and consistent force.

Here is a listing of the part numbers and correct torque settings, by transducer model number:

The tools needed are shown in the featured picture above.

Validyne offers a wide array of Pressure Sensors and Pressure Transducers. Feel free to contact us for more information on any of these products to fit your application.