Page 180 - An Introduction To Predictive Maintenance

170 An Introduction to Predictive Maintenance

Radial Extending from a point or center in the
manner of rays (as the spokes of a wheel are
radial).

Radian The central angle of a circle determined by
two radii and an arc joining them, all of the
same length. A circle consists of 2p radians.
Reciprocation The action of moving back and forth
alternately.

Signature A frequency-domain vibration curve.
Spring constant The number of pounds tension necessary to
extend the spring one inch. Also referred to
as stiffness or spring modulus.
Thermography Use of heat emissions of machinery or plant
equipment as a monitoring and diagnostic
predictive maintenance tool. For example,
temperature differences on a coupling indi-
cate misalignment and/or uneven mechanical
forces.
Torque A moment/force couple applied to a rotor
such as a shaft in order to sustain accelera-
tion/load requirements. A twisting load
imparted to shafts as the result of induced
loads/speeds.
Transducer Any device or element that converts an input
signal into an output signal of a different
form.
Tribology Science of rotor-bearing-support system
design and operation. Predictive maintenance
technique that uses spectrographic, wear par-
ticle, ferrography, and other measurements of
the lubricating oil as a diagnostic tool.

Turbulent flow Motion of fluids in which local velocities and
pressures fluctuate irregularly and randomly.
Ultrasonic analysis Predictive maintenance technique that uses
principles similar to those of vibration analy-
sis 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 20,000 Hertz
and 100 kiloHertz.