Pipe Strain

Static Pipe Strain

Static pipe strain and its effects are relatively simple to measure. One method is to disconnect the pipe flanges and measure any piping misalignment. Most companies aim for no more than 0.05mm; difference in distance between the flanges. Furthermore, the bolts should go freely through the holes to align the pipe flanges. To check for the effects of pipe strain on the machine, dial indicators should be mounted vertically and horizontally at each bearing. The dials should be checked as each flange is connected or disconnected. Any movement at the bearing of more than 0.4mm; is generally considered excessive.

Dynamic Pipe Strain

Dynamic pipe strain is much more difficult to check since it occurs while the system is in operation. It is commonly due to thermal expansion of the piping, the weight of the system fluid or both of these along with inadequate piping or piping support. Dynamic pipe strain is most often detected by using a measurement device to check for differences in machine movement between static and dynamic conditions.

How does Pipe strain cause failure?

Pipe strain causes distortion of the machine frame. As the frame or casing is distorted, so are the bearing housings, the shaft and other components. These problems can lead to excessive bearing temperatures. The bearing problems can be detected through vibration analysis, which will have bearing fault frequencies as the dominant peaks. Packing and mechanical seal performance will also be affected by pipe strain because of the additional forces caused by the distortion to the bearing bore. Anything that leads to shaft deflection or reduced bearing clearances can quickly lead to catastrophic failure, particularly of bearings and seals.