Just When You Thought You Knew Everything About Online Protection Panels – Part 3

Probe Labeling / Orientation Conventions

Labeling Convention_Displacement Probes1

Labeling Convention_Displacement Probes2

The above two diagrams illustrate the labeling convention used for displacement probes. Note: this convention assumes the viewer is standing at the NDE of the “driver” end of the machine train (e.g., a turbine, diesel engine, electric motor etc.), and looking towards the “driven” equipment, such as a gearbox, compressor, pump etc.

It is your responsibility, when obtaining data from an online protection panel, that you understand the above conventions, and that you also study the appropriate P & ID for the machine in question, to determine which probe is located where on the machine train. This is often necessary as the protection panel monitors sometimes only indicate probe tag numbers for each channel, and not necessarily where on the machine and/or the machine train they are located. This convention is independent of the shaft rotation direction.

Other Required Information

The machine train shaft direction(s) of rotation are also required, for analysis purposes. This can usually be obtained from the machine casings, which usually have a ‘direction arrow’ above the bearing housing of the driver, gearbox shaft bearing housings and the driven equipment. If these are missing, then the manufacturer’s drawings should provide this information.

In addition to the probe tag numbers, their locations on the train components, the speed, and shaft rotation direction, the probe tip diameter and probe sensitivity should also be confirmed.

The various shaft speeds are also required, bearing in mind the change of speed due to the presence in the machine train of a gearbox – either a speed-increasing or a speed-reducing one.

Online Protection Panels vs Condition Monitoring Panel Systems

Up to this point, the discussion was focused on ‘what’ an online  protection panel was and its components. There are, however, two distinct panel systems in use:

An Online Protection Panel – which is designed to shut down the machine train if/when the vibration amplitude levels reach and exceed to previously set “Danger” (or “Trip”) setpoint vibration overall amplitude level.

This type of system does not store any data, but has the functionality to transfer live data to the plant DCS or SCADA systems and the PI Historian for long term trending. This means that this type of system has very limited diagnostic capabilities – which is restricted to trend data only, because this data is 4 – 20 mA loop-powered sensor trend data only.

An online Condition Monitoring Protection Panel System – in this type of system, there are two components:

(a) the online protection panel system, as above.

(b) a computer server system, which is physically attached to the protection rack, and stores not only the analog trend data, but also the dynamic data. This allows the user the capability of analysing the vibration data, to assist in diagnosing impending faults, or reviewing faults which have tripped the machine, once it has stopped. It also allows the study of the dynamic behaviour of the various rotors covered by the system, during transient conditions.

Therefore, for the additional cost outlay, an on-line protection panel system, can be upgraded to provide the condition monitoring capabilities, which give the advantage (among other things), of being capable of predicting a machine impending failure.

This type of system has the benefit of preventing or reducing unplanned plant outages, delays due to lack of required spares, and the possibility of secondary damage; not to mention the possibility of a safety risk to plant personnel and also potentially an environmental impact from spillages of dangerous/toxic chemicals.


As described earlier, protection panel systems; which form the majority of such system
installations, is limited to sending trend data to other plant systems. They are not capable
of providing any ‘dynamic’ data such as an FFT spectrum, a Bode plot, a waterfall plot etc.

With this limitation in mind, there is the option of connecting various types of instrument to the panel monitor “buffered output” connectors, which are of various types – i.e., 4 mm
plugs, BNC connectors, and SMB connectors etc. The units are connected to the panel system using coaxial cables – one per channel.

It is these monitor connectors which are utilised in order to connect an analyser (or portable data collector/analyser) can be connected, to obtain the raw (instantaneous) vibration signals. There are a number of manufacturers of this type of equipment – from the simple data collector/analyser end of the market, through DAT tape recorders, to the more dedicated and advanced high speed data analysers. Tape recorders are now becoming obsolete in favour of newer analysers.

The image below left shows a 2-channel portable, battery-operated data collector/analyser
Unit, whilst the image on the right is of a more advanced 4-channel instrument. These instruments store the instantaneous data from the buffered output connectors, for later transfer to a computer, which has the appropriate application software and database loaded. The data is then analysed and reported using the computer application software.

Rozh RH802 2 Channel Portable Data Collector:Analyser

Rozh RH802 2 Channel Portable Data Collector:Analyser

Adash A4400 VA4 Pro 4 Channel Portable Data Collector:Analyser

Adash A4400 VA4 Pro 4 Channel Portable Data Collector:Analyser

The instrument shown below is an HGL Dynamics “Mosquito” portable 4-channel + phase data ‘streaming’ type unit, which is portable, due to its small size, and therefore more convenient for ad-hock type of work. It connects to a laptop computer, and ‘streams’ the ‘live’ data to the software database loaded in the laptop, for storage and data analysis. It has four 24-bit A/D’s – one for each of the 4 input channels, and synchronous sampling rates of up to 50 kHz, with up to 20 kHz bandwidth. It also has a dedicated tacho channel, and weighs only 0.5 kg. It is USB 2.0 powered, and streams the data to a laptop. Multiple ‘Mosquitos’ can be synchronised to offer a higher channel count, and each unit measures 110 mm wide x 175 mm long, x 15 mm high (4 ⅜” x 7” x ⅝”). Voice annotation is also possible with this unit.

HGL Dynamics Mosquito Portable 4 Channel Phase Data Streaming Unit

HGL Dynamics Mosquito Portable 4 Channel Phase Data Streaming Unit

The 8-channel HGL Dynamics “Firefly” analyser unit below, has internal storage, and a screen, to view the vibration data that has been previously or is currently being stored. This unit can also be connected to a laptop computer, and also has the ability to be “daisy- chained” to another similar unit, to allow for channel count expansion. It can be powered from the mains supply, or by using the internal battery. It has 24-bit A/D converters for each of its 8 channels, and measures 275 mm wide x 230 mm deep x 50 mm high (i.e., ≈ 11” wide x 9” deep x 2” high), with a 10.7” (1024 x 768 pixel) touch screen, and weighs 2.5 kg.
This unit also has Wi-Fi capability, as well as audio voice annotation. Tachos can be connected to any of the eight input channels.

8 Channel HGL Dynamics Firefly Analyser Unit

8 Channel HGL Dynamics Firefly Analyser Unit

This final analyser unit below, an HGL Dynamics “Dragonfly” unit, is designed for high speed data acquisition from protection panels. It is equipped with a pair of slots on the top to allow an additional (identical) units to be attached on top, in order to increase the available number of channels, by connecting a few cables (i.e., power, sync, and Ethernet). These units are < 1 kg in weight, and boast 8 individual channel 24-bit A/D converters, with a Signal-to-noise ratio of 120 dB in 24-bit mode (95 + dB in 16-bit mode), and can be expanded to reach channel counts in the hundreds. They are also small – measuring only 100 mm wide x 100 mm deep, and 44 mm high (≈ 4 “ wide x 4” long x 1¾” high).

HGL Dynamics Dragonfly Unit

HGL Dynamics Dragonfly Unit

The cards mounted internally, can be swapped out by the user, making them user-friendly. These units are compatible with IEPE sensors, displacement sensors; AC and DC coupling, and strain gauge sensors etc.

There is an option for GPS time synchronization, which allows multiple sets of Dragonfly units to be spread across large distances, while maintaining < 50 ns between GPS equipped modules, regardless of location. Alternatively, they can be synchronised by IEEE1588 for Ethernet only synchronization.

The ‘standard’ dragonfly unit above, is one of a family of modules, which can provide ancilliary functions such as CPU power, Storage via solid state or hard disk drives, Ethernet switches, battery power specialized conditioning etc.

This concludes our 3 Part Series on Condition Monitoring Panel Systems, Online Protection Panels and Transducers.  If you have any questions at all, please get in touch…we would love to answer your questions. Or why not delve deeper into Condition Monitoring, with the Handbook of Condition Monitoring: Techniques and Methodology.


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