Service & Diagnostics

MICROTEM works in the machinery sector (maintenance, service) since 2005. The service of "Diagnostic Department" has been implemented by capitalizing on decades of experience of its employees. It proposes, according to the importance of machinery, two monitoring systems.
The first concerns a continue supervision to scan the measurement points, with fixed instrumentation. The second concerns periodic measurements of machinery with portable instrumentation.
It is also able to carry out several corrective actions for the reactivation of the characteristics of good operation of the rotating machinery. In the past the maintenance techniques most widely used on rotating machines were of two types: the first "Periodic Programmed", the second "In Emergency".

The first, also performed on an apparently efficient machine, however, involves high costs and long lead times of global maintenance, while the second involves expensive production standstill, difficult to quantify. Today, modern technologies have enabled the development of a third technique: "The Predictive Maintenance" or under condition.
It is based on systematic inspection interventions and it allows an optimal planning of maintenance.

The advantages of the "Predictive Maintenance" on rotating machines are:
1. Decrease of the reserve units.
2. Through nondestructive inspection systems, on the machinery in regular production, it is possible to predict and then program the period of maintenance.
3. Often the periodic analysis of the functioning parameters may serve to improve the efficiency of the machinery.

Microtem S.r.l. proposes to its partners a customized program on the installed machines, which is based on the following guidelines:
1. Definition of the machines which compose the plant. Importance: spare, repair and evaluation of production standstill. Evaluation of the loading and of the characteristic parameters of operation.
2. Measure of vibrations.
Analysis of "natural vibration" frequencies (Resonance) of the complex machine.
Investigation of vibrations from adjacent machines.
Analysis during start (start-up) and stop (cost-down).
Analysis during no-load operation and during various operating loads with survey of transients.
Technical corrections of the system, if the result is not suitable for the operation.
3. Definition of the measurement parameters.
Mode of operation for acquisition.
Acquisition points.
Types of probes and their anchorage to the machinery.
Units of measurement, frequency range.
4. Definition of the periodicity of the surveys: depending on the importance of the machinery; it is usually more frequent in the first phase, to focus on the vibratory system of good operation.
5. Definition of the vibratory system and of the alarm thresholds. Once the meaningful load for the surveys is defined, often with at least 5 measurements, the vibratory system of good operation is established. Two thresholds values are set: an "alert" which is usually indicative of eligibility for the operation, and another "alarm", which indicates the inadmissibility operation.
6. Instant reports.
At the end of each programmed survey a report will be issued in which it can be read clearly the level of good operation of the machine and its trend vibratory.
Causes of vibration and noise of rotating machines are attributable to:
• Initial imbalance or detachment of the rotating parts.
• Bending of the shaft.
• Misalignment between contiguous shafts.
• Loosening of the anchor bolts.
• Vibration generated by gaps and tolerances.
• Deformations of the cases and of the foundations.
• Friction of seals, stuffing box, etc.
• Forces resulting from pipes.
• Eccentricity in bearings and bushings.
• Damage to radial bearings or to thrust bearings.
• Unequal rigidity, hor./vertic., of the bearings.
• Imprecision in joining the mechanisms.
• Geometric imprecision of the mechanisms.
• Rotor critical speed.
• Coupling critical speed.
• Overhang rotor critical speed.
• Subharmonic resonance.
• Harmonic resonance.
• Resonance of the case, of the support, of the bearings and of the foundation.
• Torsional resonance.
• Belts in bad condition.
• Alternatives forces.
• Aerodynamic and hydraulic forces.
• Turbulence generated by friction.
• Turbulence due to the lubricating oil.
• Turbulence due to resonance.
• Eccentricity of the rotor.
• Misalignment of the rotor/stator.
• Stator with elliptical boring.
• Defective rotor bars.
• Elliptical eccentricity of the rotor.
• Vibrations caused by adjacent machines.


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