Basic Concepts of Vibration Analysis

What is Vibration?

Introduction

Vibration is the disturbance from equilibrium, which propagates in time from one place to another and exists in all rotating and reciprocating machinery. An ideal machine would produce no vibration at all because all energy would be channelled into the machine function. A good design will produce low levels of inherent vibration, however, as the machine wears, foundations settle and parts deform, subtle changes in the dynamic properties of the machine begin to occur. Shafts become misaligned, parts begin to wear, rotors become unbalanced and tolerances increase. All of these factors are reflected in an increase in vibration energy, which dissipates throughout the machine, excites resonance and puts considerable strain on bearings. Cause and effect reinforce each other and the machine progresses towards ultimate breakdown.

A machine may contain many complex vibrations, made up of a wide-range of superimposed sinusoidal and random components. This multi-complex signal can be broken down into its constituent frequency components by using F.F.T. analysis (Fast Fourier Transform) commonly referred to as a Spectrum. Since every fault and deviation has their own signature component so by analysis and understanding the signature component one can assess the health conditions of assets.

The Vibration Monitoring Process

The process begins by identifying critical assets and their effects on production through our custom designed criticality tool. Based on the equipment identified and the manufacturer’s recommended operational parameters, a proper frequency of vibration monitoring can be obtained. Once created, field technicians will routinely come to your facility to conduct the vibration monitoring to ensure proper data collection.

The vibration monitoring and analysis from the machinery will allow for timely detection and repair of such operational issues and flaws as:

  • Failing Bearings
  • Unbalances
  • Misalignments
  • Gear Problems
  • Electrical Problems
  • Out-of-Round Journals
  • Bent Shafts
  • Looseness
  • Impeller Problems
  • PLUS many other causes

Vibration Monitoring Services Offered from us:

  • Audits – We’ll assess your plant and give recommendations and requirements.
  • In House Systems – We can assist you in the best way to setup and maintain your own in house vibration monitoring program.
  • Vibration Monitoring Service – Routine data collection, analysis and reporting carried out by us.
  • Vibration Analysis – You collect the data and we will analyze it and report back our findings.
  • Trouble Shoots – One off diagnosis and analysis of machine vibration problems.
  • Commissioning – A full vibration monitoring report prior to plant handover and acceptance.
  • System Setup – No matter whose product you have we can assist in setup and best practice.
  • Machine Vibration Benchmarking – We will help you for benchmarking your machine vibrations according to industry and similar operating conditions.
  • Balancing – We can balance machinery in-situ.

What is ‘In-situ Dynamic Balancing’?

In-situ (or on-site) balancing is a form of rotational balancing which is achieved on site. Similar to car tire balancing however on an industrial scale, most impellers/rotors will develop imbalance due to many factors; some unavoidable. It can be detected using Vibration Analysis. In static imbalance, there is a single heavy spot in the unit which generates an imbalance force; by applying a balance force in the opposite direction, the two forces cancel out leaving the unit neutral and free of imbalance.

Coupled imbalance can occur with larger plane distance (long rotors for example), this is where there are two static spots on opposite planes are creating the imbalance forces. This can be described as a ‘twist’ in the unit balance. A combination of both coupled and static is where the opposite planes are out of sync and one side is also heavier than the other, this is called Dynamic Imbalance.

What are the benefits of ‘In-situ Dynamic Balancing?

  • Reduce maintenance costs – Imbalance is a large factor in reducing the lifespan of bearings and other mechanical components, therefore by balancing machinery, these components last longer.
  • Reduced energy costs – units running out of balance generally consume more power as the driver must work harder to compensate, balancing will reduce overall energy costs
  • Noise/vibration reductions – Imbalance causes higher vibration and noise levels which can be greatly reduced once a unit is balanced.
  • No removal required – The unit does not need to be stripped and removed for in-situ balancing, reducing the repair cost of some machinery. However, not all dynamic imbalance can be rectified on-site due to physical restrictions; some may require a Workshop Balance.

Our services include On-Site Dynamic Balancing of all types of rotating components such as:

  • Generators
  • Compressors
  • Turbines
  • Pump impellers
  • Motor rotors
  • Gears
  • Crankshafts
  • Fans and blowers
  • Process rolls
  • Air Pulleys and sheaves
  • Bearing spindle assemblies
  • Printing drums
  • High-speed tooling
  • Cutting tools

Balancing: Single, Dual and Multiplane Vibration Balancing

Single/Dual Plane Balancing

  • 1 or 2 balancing planes
  • Rigid rotors
  • 1 to 4 sensors (1 or 2 per bearing)
  • Real time acquisition and 1X polar diagram (amplitude and phase)
  • Steady state speed acquisition
  • Acceptance of residual unbalance according to ISO 1940 / balancing quality selection
  • Size and weight: optimum size with OR34. Runs on the 3-Series instruments’ platform
  • Trim Balancing
  • Report generation
  • Designed for non-experts

Multiplane Balancing

  • 1 to 14 planes
  • Flexible or rigid rotors
  • Up to 32 channels for 1X acquisition
  • Run-up, Coast-down, steady-state
  • Balance at multiple speeds or ranges of speeds
  • Calculate predicted Amplitude vs. RPM after balancing correction
  • Multiplane report generation

Laser shaft alignment is a form of corrective maintenance. A modern replacement of traditional DTI (clock-gauge) alignment, taking a significantly less amount of time and having greater accuracy, it is the way forward in shaft alignment. A misaligned machine creates a damaging force in particular angles within the rotation, this force causes damage over time to various parts of a machine (coupling, bearings, seals, gears, etc…) Alignment uses a laser and a receiver which measures the lasers displacement upon rotation, giving correction values which can be performed to ensure the machine is then properly aligned and the damaging forces are reduced significantly.

Benefits of Laser Alignment

There are many benefits to why laser alignment is performed:

  • Significantly extends MTBF (Mean Time Between Failures) – the average time between failures is increased by laser alignment by reducing the damaging forces which machines are often left subject to. These forces are constantly applied to crucial parts of machinery such as the bearings, coupling, gears and seals.
  • Reduces operational temperatures – operating temperatures are often increased by misalignment forces, this temperature increase can lead to premature failure and unnecessary downtime. Couplings often show the highest increase of temperature due to misalignment, therefore coupling life is significantly longer once correctly aligned.
  • Warranty purposes – when installing a new machine, it is often written in the small print of the warranty information that; if installed and not aligned correctly, the warranty may be void. Even new machines aligned at manufacturers require a new alignment once installed on site.

Applications for Laser Shaft Alignment

Laser Shaft Alignment offers benefits in any industry where rotating equipment applications are deployed:

  • Alignment Shafts
  • Alignment Measurement
  • Alignment Shims
  • Coupling Alignment
  • Drive Shaft Alignment
  • Foundation Settlement
  • Gearbox Alignment
  • Horizontal Alignment
  • Motor Alignment
  • Prop Shaft Alignment
  • Pump Alignment
  • Roll Alignment
  • Vertical Alignment

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