• Unit 3A, Adwick Park, Swinton, Rotherham S63 5AB

Vibration Data Collection

Vibration Data Collection

When evaluating machinery health, the analyst should:

  • Visually inspect each machine for the overall condition of the machine, such as leaking seals, other damaged or incomplete components, cracked welds, deterioration in the grouting, missing clamps and hold-downs while visiting the site to collect vibration data.
  • Ensure that you can determine the turning speed (TS) at the measurement point location before any critical measurement is taken.
  • Once TS is identified, determine TS harmonic relationships
  • When harmonics of TS are determined, other vibration peaks of interest and other harmonic relationships may be identified for analysis

Resonance

Every machine will vibrate when excited by a forcing function. Each machine has one or more natural or resonance frequencies. When any forcing function is near the natural frequency, the resulting vibration will be significantly amplified and could cause premature failure.

A critical speed is when the rotating element is turning at a speed which excites resonance in the machine. Many times a forcing function (such as from a rotating shaft) excites a resonant frequency in another part of the same or nearby machine. This resonant frequency may be identified by an impact test, typically when the machine is off; the machine structure may be “rung” like a bell. Changing a structures stiffness, mass, damping, operating speed and/or reduction of the forcing function will affect the resonance issue and may help sort the problem.

Resonance is an increasing problem in industry because:

  • New equipment is often built lighter
  • More variable speed machinery is being used in industry
  • Machines are often now run at a higher speed

For more information about our services please contact us:

T: 01709 876712 E:info@pcmseng.co.uk

 

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Electric Motor Diagnostics

Electric Motor Diagnostics

Heat and fatigue, associated with excessive motor starts or overloading can lead to broken rotor bars in electric motors. Broken rotor bars eventually lead to motor failure, and can cause secondary damage to stator windings. Rotor bar damage can be difficult to detect in a vibration signature. Emerson’s CSI Motor Diagnostic technology, with embedded analysis expertise, helps complete a total Machinery Health Management programme by diagnosing electrical problems that may be missed with a vibration monitoring programme alone.

Motor current analysis provides information on rotor-related electrical faults such as broken rotor bars, high-resistance joints, voids in aluminum cast rotors, and cracked rotor end rings in squirrel-cage induction motors.

In addition to motor current analysis, Emerson’s motor monitoring tools also include motor flux analysis. Monitoring the magnetic flux field of the motor provides the safety and convenience of not having to open motor control cabinets to access electrical wiring directly, and provides detection of additional electrical problems related to the motor stator that are not found in the current signature. Temperature measurements also play an important role in the overall motor condition analysis and are incorporated into the automated analysis.

The tools are non-intrusive and perform motor current analysis, motor flux analysis and temperature measurements while motors remain online. Motor signature data is transferred to AMS Suite: Machinery Health Manager for automated expert analysis, trending, comparison with results from other diagnostic technologies, and implementation of corrective actions.

For more information about our services please contact us:

T: 01709 876712 E:info@pcmseng.co.uk

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Detecting Imbalance, Misalignment And Looseness

Detecting Imbalance, Misalignment and Looseness

Imbalance is the condition of a rotating component where the center of rotation is not the same as the center of mass.

Looseness is characterised by harmonics of TS with raised noise floor. Waveform displays random impacting which may be in a non-repetitive irregular pattern. Highest amplitudes typically occur in the radial direction, specifically the vertical plane for horizontally mounted equipment.

The number of turning speed harmonics and their amplitudes increase with the severity of the problem.

Unstable phase characterises looseness.

 Fractional harmonics may develop due to looseness.
 Common causes of imbalance:
  • Material buildup
  • Wear
  • Broken or missing parts
  • Improper assembly or poor design
  • Thermal distortion
Imbalance vibration is always at 1x turning speed (TS).
  • Turning speed peak amplitude increases with icrease in speed
  • Little axial energy except with overhung machines
  • Little or no turning speed harmonics.
  • Simple, sinusoidal, periodic waveform
  • One event per shaft rotation
  • Little or no impacting

Misalignment is when rotational center lines of coupled shafts are not colinear.

High, 2 x Turning Speed (TS), peak characterises offset misalignment; a high 1 x signifies angular misalignment, though both frequently combine to cause 1 x TS and 2 x TS in the spectrum. Highest amplitudes typically occur in the radial direction for horizontally mounted equipment; over hung rotors may exhibit higher amplitudes in the axial plane.

For more information about our services please contact us:

T: 01709 876712 E:info@pcmseng.co.uk

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Vibration Transducer

There are different methods which can be used to connect a vibration transducer to a piece of equipment. In order of preference, these are:

The vibration transducer is screwed onto a threaded stud which is attached to the machine, typically by drilling and tapping a hole, or by stud welding. Is commonly used only with inaccessible systems and online systems.

Adhesive Mounting

As an alternative to stud mounting, vibration transducers can be glued to the equipment using suitable adhesive.

Magnetic Mounting

Commonly used for route based monitoring or other temporary data collection, magnetic mounting involves connecting the transducer to a magnetic base which is then magnetically attached to the equipment. This method can only be used if the mounting location is ferromagnetic.

Hand Held Probes

Hand held probes wield the poorest results and are not recommended but are sometimes necessary because of access restrictions or safety concerns.

There are three main types of vibration transducer.

For more information about our services please contact us:

T: 01709 876712 E:info@pcmseng.co.uk

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Vibration Analysis For Machinery Health Diagnostics

Vibration Analysis For Machinery Health Diagnostics

Vibration is movement relative to a reference position, such as the centre line of a shaft on rotating equipment. It is a result of an excitation force or forcing function and may be either random or periodic. This is why vibration analysis for machinery is important to undertake.

Vibration monitoring can often pinpoint a failing element of a rotating machine in time to avoid catastrophic failure and costly replacement of machinery as well as lengthy production interruptions.

  • Each machine fault generates a specific vibration pattern.
  • The frequency of the vibration is determined by the machinery geometry and operating speed.
  • A single vibration measurement provides information about multiple components.

Vibration Monitoring Can Identify The Following Problems

  • Imbalance
  • Belt Problems
  • Resonance
  • Oil Whirl
  • Vane pass
  • Cavitation
  • Misalignment
  • Rolling element bearing defects
  • Electrical Problems
  • Sleeve bearing problems
  • Flow problems
  • Lubrication problems
  • Gear problems
  • Looseness
  • Rubs
  • Oil Whip
  • Blade pass
  • Pipe Strain

Vibration monitoring is used to improve profitability in every major industry in the world.

For more information about our services please contact us:

T: 01709 876712 E:info@pcmseng.co.uk

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