Page 315 - Root Cause Failure Analysis

Glossary 303

thrust Axial forces and vibration created by the
mechanical or dynamic operation of machine
trains or process systems.
top event A system failure in a fault-tree analysis; it can he
either a broad, all-encompassing failure or a
failure of a particular component.
torque A moment/force couple applied to a rotor such as
a shaft to sustain acceleratiodload requirements.
A twisting load imparted to shafts as the result of
induced loadslspeeds.
torsion A straining action produced by couples that act
normal to the axis of a member, identified by a
twisting deformation.
total system head The total pressure required to overcome all
downstream resistance at a given flow.
transformer An electrical component required when a
different input or output voltage is needed for
proper operation of equipment.
transient An event such as an impact or change in speed
or process parameter that varies in time. A
temporary phenomenon occurring in a system
prior to reaching a steady-state condition.
turbulent flow Motion of fluids in which local velocities and
pressures fluctuate irregularly, in a random
manner.
ultrasonic analysis Testing technique that can be used to measure the
cause-and-effect relationship between variables.
It uses principles similar to those of vibration
analysis to monitor the noise generated by plant
machinery or systems to determine their actual
operating condition. Ultrasonics is used to
monitor the higher frequencies (i.e., ultrasound)
that range between 20,OOO Hz and 100 kHz.

unloading Depressuring or emptying a process unit.
vane Casting on the backside of the impeller that
reduces the pressure acting on the fluid behind
the impeller.
variable Data item or symbol that can assume any of a set
of values.