Top 25 MCQs on Turbine Supervisory Instrumentation (TSI) for Instrumentation Professionals

Verifying vibration amplitude with phase data from the keyphasor helps to separate actual mechanical vibration from noise or signal drift, hence lowering false alarms.

High-high alarms signal major mechanical problems when vibration above a predetermined trip threshold. Usually, the system shuts down to safeguard the equipment.

Derived from XY probe data, orbit plots show the rotor’s motion in a 2D plane, hence assisting in the diagnosis of imbalance, misalignment, and looseness.

Differential expansion monitors the relative movement of rotor and casing during thermal cycling, which is vital in spotting misalignment concerns as temperatures vary.

Usually, if the controller keeps a consistent signal but the valve position feedback falls, it indicates a mechanical problem such valve stem jamming or linkage failure.

Before the turbine accelerates, rotor eccentricity has to be within limitations. TSI systems stop catastrophic imbalance during ramp-up using eccentricity readings.

Rotor imbalance is characterized by 1X frequency once every revolution as it indicates the basic frequency of the spinning shaft.

Often slowly rising with speed and rotor thermal stabilization, rotor angle causes vibration amplitude to vary.

Thrust bearings stop axial rotor motion. Should they fail, TSI systems detect a rapid axial change and start instant shutdown operations.

Keyphasor signals let you specify the angular reference point for every rotor revolution. Orbit plots and phase-based vibration analysis depend on this.

Vibration probes are installed in X and Y orientations (90° apart) at every journal bearing to completely catch radial shaft movement.

Differential expansion beyond threshold values can suggest unusual heat growth between the rotor and the case, perhaps causing rubbing or mechanical contact.

The turbine rotor has to be carefully turned after shutdown to provide consistent cooling and prevent thermal bending. TSI keeps track of this situation utilizing slow-roll data and eccentricity.

LVDTs provide precise linear displacement measurement. TSI monitors valve stem movement to confirm control and emergency valve placement during start-up, shutdown, and trips.

A growing shaft crack’s typical signature is a 180° phase change and a rapid rise in vibration amplitude. This may point to a major structural shift in the stiffness profile of the rotor.

XY vibration probes identify radial shaft movement in two orthogonal directions. Key signs of rotor imbalance, misalignment, or looseness are high vibration amplitude and phase change.

To safeguard the rotor from too much centrifugal force and catastrophic mechanical failure, overspeed protection trips are often set at 110% of the rated speed.

Keyphasors provide a once-per-revolution signal to match with vibration data. Phase angle calculation and imbalance or misalignment diagnosis depend on this.

Ideal for tracking the relative position between rotor and casing in differential expansion systems, Linear Variable Differential Transformers (LVDTs) offer exact linear displacement readings.

Steam heats the turbine shell, causing it to expand. Expansion sensors guarantee that mechanical structures such support legs and alignment systems can consider this motion without misalignment or binding.

Uneven temperature gradients can cause the shaft to bend somewhat, which is known as rotor bending. Before permitting turbine acceleration, this eccentricity can be monitored and fixed.

The turbine’s warming causes the rotor and casing to expand at different rates. Differential expansion sensors guarantee that the rotor doesn’t bind or touch the casing, particularly during starting and shutdown.

Thrust bearings govern axial shaft movement. Wear or damage can make the shaft dangerously forward or backward, hence harming seals or blades.

Eddy current probes produce an analog voltage corresponding to the distance between the sensor and the spinning shaft, hence enabling vibration and position analysis by downstream signal conditioners.

Detecting high-speed, exact shaft movement is best done with non-contact type Eddy current probes. Important in TSI systems, they can monitor eccentricity (slow-roll runout) and vibration (radial).