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Compressors are widely used in industrial processes to compress air and other types of gases. These machines have a wide range of applications in industries, going from compressed air supply for general applications to very specific ones, such as cooling of cold rooms in food processing industries. As equipment that generally work with high speeds and small clearances between its components, constant monitoring of this type of machine is recommended and can assist in anticipating potential faults.

One of the predictive techniques that can be used for compressor monitoring is vibration analysis. Manufacturers commonly inform the monitoring spots on this type of machine. In general, the monitoring spots are indicated on the compressor input shaft (as close as possible to the gears and bearings), as shown in the figure below. DynaLoggers HF sensors are the most recommended for this task, since the compressors generally operate at high speed and their faults usually appear at higher frequencies. If vertical mounting is not possible, horizontal spots can be chosen.

Gearboxes are used to increase or decrease the speed of a drive system or simply change the direction of rotation. A variety of problems in this type of system can be detected by vibration analysis, such as:

• Gear teeth wear
• Excessive load on teeth
• Gear eccentricity and / or looseness
• Cracked or broken gear teeth
• Hunting tooth problems

One of the main frequencies of interest when evaluating the integrity of the gears will be the gear  meshing frequency (GMF =  number of teeth X RPM), mainly monitoring the frequency amplitude increase and the relationship with its harmonics. However, it is important to note that the GMF, by itself, is not a fault or defect frequency. All gears generate frequencies of a certain amplitude. In addition, all gearing frequencies have sidebands of some amplitude. Thus, the analysis must be based on prior knowledge of the breadth of healthy machinery and must be carefully analyzed by vibration analysts.

More specifically, a reduction set is composed of 4 main components 

• axes: the amount of which depends on the number of gears,
• gears: whose relations of number of teeth and reduction or increase ratio in the rotation speed, 
• bearings: allow the shaft ends to not wear out and 
• housing: houses all these elements. 

It is common for analysts and maintenance managers to be concerned with checking vibration data only for the set of gear meshes and often end up ignoring the bearings. However, in the event that one of the bearings fails, the entire system will be compromised, possibly even causing damage to the gear set.

With the implementation of the Dynapredict Solution, it is possible to continuously monitor the amplitude evolution in the frequencies connected to the GMF , as well as bearing defects. In order to have greater precision and reliability of the acquired data, it is recommended to install the DynaLogger HF sensor model in each bearing present in the gearbox. Still with regard to sensor mounting, it is indicated to avoid sensor positioning on screwed covers and preferably choose rigid spots at the housing, always as close as possible to the element to be monitored.

(Sensors shall be mounted on both sides of the equipment)


Table 1 – Typical fault frequency and its causes

Blowers and fans are equipment used for ventilation, aeration, exhaustion, cooling and drying in various production processes in the most varied industries.

The fans are subject to forces generated by their operating speed, static pressures and system arrangement. These forces, called operational forces, cause forced vibrations and can originate from the rotating parts themselves. Unbalanced fan wheels and driving pulleys are examples of forces that can cause unbalance and misalignment. Another example is the axial load on the fan bearings, which is mainly generated by the negative static pressure at the inlet of the fan blades.

Due to the process in which this type of system is used, the most common fault modes are: unbalance, misalignment, eccentric pulleys, looseness and belts wear and structural looseness, identified at low frequencies. Also, some bearing problems, especially premature wear and tear generated by the fault modes mentioned above, can occur.

The DynaLogger TcAs, with its frequency range up to 2.5 kHz, is capable of identifying the mentioned faults, but the detection of bearing faults will occur at a more advanced stage. For detection in earlier stages and also for lubrication faults or electrical faults related to the rotor and stator, it is recommended to use the DynaLogger HF+ due to its larger frequency range, up to 13 kHz.

It is important to mount DynaLoggers on all bearing housings or rigid parts for effective monitoring. Avoid mounting sensors on flexible surfaces, on curves or that have localized resonance such as protective covers and fins.
 

Table1 – Typical fault frequency and its causes

Centrifugal pumps are hydraulic machines, which consist usually of rotating elements (e.g., pump impeller, bearings, electric motor) and stationary elements (volute/casing, diffuser, stay/guide vanes, and housing bearing), which can generate fault frequencies from mechanical and hydrodynamic sources. Mechanical sources are generated by the rotation of unbalanced masses and friction in the bearings. Hydrodynamic vibration, on the other hand, is usually caused due to flow disturbances, generated by the interaction of the rotor blades, particularly with the volute and / or guide vanes.

To predictively monitor the vibration and temperature parameters, two models of sensors can be used
DynaLogger HF+ and  DynaLogger TcAs 

The DynaLogger TcAs model can be used specifically in motors, where it will be used to identify structural defects, looseness, electrical faults and stage 3 bearing defects. In the Pump bearings, due to the faults high frequencies, the use of the DynaLogger HF+ is indicated. The number of sensors is directly linked to the number of bearings and the mechanical seal. Always try to mount the sensors as close as possible to the bearings, avoiding noisy signals and flexible parts, which can increase the reliability of the analysis.

Table 1 – Typical fault frequency and its causes

Here are pictures of actual installations of the sensors:

The main purpose of generator sets is to provide electrical energy, continuous or temporary (in cases of emergency), safely and effectively. The generator sets serve not only to supply energy to unsupported regions, but also to be activated in cases of emergency, avoiding various losses due to power outage.

Small generators generally use common rotating elements, in which case the vibration behavior and fault diagnosis is similar to that of a large electric motor. The vibration data measurement requirements for diesel powered generators should normally be in accordance with ISO 10816 part 3.

Measurements must be made on each bearing housing and on the crankshaft bushings. Avoid mounting sensors on the protective covers or at the equipment base. The frequency range must be enough to cover from 2 Hz to at least 2x the frequency of the fanspeed, with a minimum range  up to 2 kHz, according to ISO 10816. Therefore, for the monitoring of diesel generators, it is recommended to use the DynaLogger HF+ model, due to its high spectral range that can reach up to 13 kHz for uniaxial and triaxial measurements.