Case expansion should be measured by a pair of LVDTs. This provides information on the position of both of the sliding feet on the machine case. This allows for a comparison of readings preventing damage should one foot become obstructed or jammed. Case expansion measurements also allow determination of whether expected thermal growth differentials are being exceeded on the machine. This is primarily a startup parameter allowing the machine casing and rotor growth to increase at a similar rate. Thermal growth at different rates can cause internal rubbing between rotating and stationary parts of the machine.
How a case expansion transducer works:
The spring loaded rod in the LVDT presses against the machine, and as the machine case grows the rod moves inside the LVDT. The change of position of the rod causes a change in the output signal of the LVDT. The signal is conditioned electronically and is output to a monitor for display and alarms. CMCP's Linear Variable Differential Transformers have a range of 0-2 inches. The output is 1-6 VDC, or 2.5 mV/mil. High temperature and extended range models are available, please call your representative for details. The CMCP-LVDT-51A has the same footprint of the discontinued CMSS-51A, and will work as a replacement for all other manufacturer's LVDTs.
