Condition Monitoring
JD Alpha Services additional services to the minerals processing community has expanded from their inhouse developed Vibrating Screen Dynamic Analysis to now include Condition Monitoring of crushing and screening equipment as well as pumps. Conveyors with their new investment of test equipment and the latest C-Trend II condition monitoring and reporting software.
Unlike other condition monitoring companies, JD Alpha Services specialise in mining, quarrying and processing industries with an in-depth knowledge of not just the equipment but the whole process.
Not just providing a nice looking report with graphs not advising the real state of the equipment, we comment on the process and why the reading may vary, and whilst we are gathering the data, if something appears out of range with previous readings our equipment allows us to re-take the measurement to make sure that it is a correct reading rather than a poor reading. We also look at the process when the reading is being taken to make sure that the event is not due to surge loading but rather it is a representative loading or plant operation reading.
Benefits:
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Find machine faults before they stop your machine
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Increase productivity and lower maintenance costs
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Measure temperature to determine if a bearing requires lubrication, preventing wear and failure
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Use temperature measurement to confirm a high BDU reading (bearing noise) is caused by a worn bearing and not noise from pump cavitation, gearbox noise, or a nearby noisy bearing
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Temperature measurement aids in diagnosing a tight or loose housing or shaft fit on a bearing
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Measuring temperature assists with potential electrical issues on motors such as winding insulation deterioration, single phasing, broken rotor bars etc.
C-Trend II software gives you greater ease of use and flexibility.
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Store analyse and report on all your vibration parameters in one place.
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All information is just a click away. Colour coded alarms highlight problems. Trend lines show problems before they happen
Vibration & Temperature readings
Once a vibration reading has been taken, the display will show four values, as shown in the example screen opposite. The values are colour coded to show their alarm status as explained in the following sections.
The four values shown in the readings screen are:
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ISO value (velocity in mm/second or inch/s)
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Bearing Noise in BDU (Bearing Damage Units)
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Total g (acceleration)
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Temperature
These readings are explained in more detail below with some examples of what they actually mean:-
ISO value (mm/s)
The ISO value (in mm/s or inch/s) is the large number displayed at the top of the screen, which is the RMS (average) of the vibration velocity in the frequency band 10Hz (600 RPM) to 1kHz (60,000 RPM) or 2Hz (120 RPM) to 1kHz (60,000 RPM), as specified by the ISO standard1. The correct frequency band is automatically selected by the meter based on running speed.
The ISO value background is colour coded according to the ISO 10816-1 vibration velocity level chart (see below). The colour coded background indicates the condition of the machine according to the size and type of machine
ISO Value toggles with Displacement
1 ISO 1016-1:1985. Mechanical vibration – Evaluation of machine vibration by measurements on non-rotating parts
Bearing Noise (BDU)
Below the displayed ISO value and to the left is the value of bearing noise (high frequency vibration) in Bearing Damage Units (BDU), where 100 BDU corresponds to 1g RMS (average) vibration measured above 1kHz. This is a measure of the wear state of the bearings in the equipment being monitored. The higher the number, the more worn the bearing.
It is commonly held that 1g of high frequency vibration (100 BDU) corresponds to a relatively high level of bearing noise and so can be considered indicative of a damaged bearing. In other words, it may be helpful to think of the Bearing Noise figure as being very roughly equivalent to “percentage” of bearing wear. By default, the bearing noise is displayed on a Red background if it is above 100 BDU, an Amber background between 50 and 100 BDU and a Green background below 50 BDU.
Total acceleration (g)
This is the RMS (average) value of the total vibration acceleration measured by the meter over its entire frequency range (2Hz to 10kHz). This reading is shown in units of g (Earth’s gravitational constant, where 1g = 9.81 m/s2).
Displacement
Displayed RMS displacement in mm toggles the display with the ISO value (mm/s).
Temperature
The measured temperature will be displayed at the bottom of the LCD. When a vibration measurement is started there will be a 10 second countdown which allows the temperature sensor to stabilize. After the countdown the temperature will be displayed.
Vibration Analysis
Additional to the displayed information provided immediately after taking the measurement, further details are recorded and displayed as required as well as being recorded in the downloaded data in the software for reporting.
Readings of vibration velocity (mm/s), or displacement (mm) if selected are broken down into each of 3 bands.
The display shows the vibration level in frequency ranges that are all based on multiples (1X, 2X and 3X) of the specified Run Speed of the machine as displayed beneath the 3 bar graphs.
N.B. in order to perform a vibration analysis it is important that the running speed of the machine is entered correctly.
The frequency ranges of the VA bands are based on the following multiples of running speed2:
1X = Unbalance:
The frequency ranges of the VA bands are based on the following multiples of running speed2:
The level of vibration in the frequency band based on the running speed is usually indicative of how well balanced the machine is. A large vibration at the running speed usually indicates that the machine is out of balance. However even a very well balanced machine will typically show some vibration at the running speed but this figure should ideally be quite low (e.g. typically less than about 2 mm/sec for a medium sized machine).
2X = Misalignment:
A high level of vibration in the frequency band centred at twice the running speed is a possible indication of misalignment. This is based on the fact that shaft misalignment can result in a double peak in the waveform due to there being two different centres of gravity (one from each shaft). In other words the accelerometer picks up a peak as each centre of gravity passes by and hence there will be two positive and two negative peaks each revolution of the shaft. This will typically give rise to a vibration signal at double the running speed of the machine.
3X = Looseness:
High vibration in the frequency band centred at 3 times running speed is a possible indication that something may be loose (e.g. loose mounting bolts, weak foundations etc.) as it is not usual to see third order vibration in a machine unless there is some structural looseness that is being “excited” by the vibration of the machine.
