24765-01-01 Bently Nevada Case Expansion Transducer Assembly

Description:

An important position measurement in Turbine Supervisory Instrumentation (TSI) is case expansion. Case expansion (sometimes referred to as shell expansion) is the thermal growth of the machine case as it expands during machine startup and on-line operations.  The case expansion transducer system is typically mounted on the foundation at the opposite end from where the turbine casing is attached to the foundation and provides information about the growth of the machine case relative to the foundation. Case expansion is a parameter that you should use a dual transducer arrangement to measure.  This arrangement provides information about the position of the sliding feet on the machine case.  A condition that obstructs or jams one foot could distort the case and damage the machine.  The dual case expansion transducer configuration in conjunction with the 3300 or 3500 monitors provides an alarm for this condition.  The high temperature dual case expansion transducer configuration is compatible only with the 3500/45 Position Monitor.

Case expansion measurements also enable you to determine whether machine conditions are exceeding expected temperature growth differentials.  This is primarily a startup parameter that determines whether the machine casing and rotor grow thermally at nearly the same rate.  Different rates of thermal growth can cause the rotating and stationary parts of the machine to rub. The case expansion transducer assembly consists of a linear variable differential transformer (LVDT), which is housed in a weatherproof, protective enclosure.