Dynamic Wire Free Strain Gauge Monitoring System (DSGS)

as used in Marine Environments

The Challenge

We have an application regarding a large hose (rubber/fabric layers that is bonded to a steel nipple) used in a marine environment. The hoses are used to transport oil from ship to ship or ship to buoy (ID of around 20 " & wall thickness around 1.5"-2"). When the operation is completed the hose is reeled up on a drum that is about 7-8m in dia. The hose will be filled with some fluid; it could be seawater or oil. We need to be able to put some sensor in the region where the steel nipple and rubber are in close proximity and be able to sense the strain levels as the hose is being reeled up. We are dealing with large deformations. Can you sensors handle this kind of application? If so, are they difficult to put inside the pipe?

Our Solution
A load cell can be constructed to withstand the large deformations. A stainless steel strip configured into a load cell can be bonded at each end to the interior of the hose (or one end bonded to the steel nipple and other end to the hose). The amount of force read by the load cell can be simply correlated to the amount of strain/stress in the hose material. This will reinforce the area around the load cell and this also will introduce a strain gradient around the bonds. If the reinforcement and higher strains around the bonds can be tolerated, then the load cell will work. An alternative would be converting a steel hose coupler into a load cell and similarly correlating the force into strain/stress. Another alternative would be to use a flexible inductive displacement (LVDT) gage and convert the displacement into a strain/stress with the hose material properties.