Condition Monitoring, Predictive Analytics Materializing in the IoT

Most manufacturing operations would put maintenance on the top of their pain lists. While unexpected maintenance from a breakdown can be catastrophic in terms of cost and lost time, predictive maintenance can also be expensive, particularly if its unnecessary. Today, more manufacturers are using technology to monitor parts and operations in order to reduce expenses and downtime — even from planned maintenance. The Internet of Things (IoT) is going a long way toward improving the gains that machine-to-machine communications have promised for a long time.

While the Internet of Things is a relatively new idea, machine-to machine (M2M) communication is not, Sean Riley, global industry director for manufacturing, supply chain and logistics at Software AG, told Design News.

The ability to perform the analysis at speed and scale has been available for at least 10 years; however, the cost and the ability to implement this type of solution quickly and efficiently have just come about, he said. What is new is the ability to leverage the enabling technology extraordinarily cost-effectively and efficiently.

The enabling technology includes analytics that help make the jump from condition monitoring – understanding whats going on right now in industrial machinery – to predicting which parts are going to fail and when.

While condition monitoring is akin to real-time diagnostics, it doesnt help predict failures, but its absolutely critical to ensuring that when a failure is predicted, the root cause and overall impact are understood, Riley told us. In the past, condition monitoring has focused on single pieces of equipment or sensors. As part of a predictive maintenance program, condition monitoring analytics now provide a critical evaluation of total line health as well as single-component and single-machine health. It also serves as a real-time aggregation function for condition data to be fed into a dynamic predictive model.

The result is a continuous streaming analytics engine that provides automated alerts on the forecasted failures identified by the predictive models. From here, companies can schedule planned maintenance with a high confidence level that the effort – and the new part — wont be wasted. Predictive monitoring is particularly suited for critical machinery, machinery that is complicated to maintain in terms of labor costs, or machinery with components that are expensive or difficult to obtain quickly.

There are also benefits from an inventory standpoint: spare parts and components can be reduced because needs are predicted weeks to months in advance.

This allows for critical components to be maintained at minimal levels around the world or ordered on-demand with the confidence that they will not be immediately needed, said Riley. Supporting this is the streamlining of the ordering process. Its critically important for a manufacturer to automate this process to ensure that a failure does not occur because a manual process broke down when acquiring a spare component or part.

READ MORE ARTICLES ON THE IOT:

At this point, it makes sense for manufacturers to look into networking with parts suppliers electronic catalogs to expedite and even automate ordering in advance of planned maintenance based on failure predictions.

Colorado-based Digabit offers a cloud-based electronics parts catalog solution with a visual interface that can add an e-commerce element to ordering parts, and even – going forward — potentially automate it based on condition monitoring and predictive analytics.

We are basically at the point where we have the hardware and software to enable machines to diagnose their own operating conditions — via sensors — and determine when parts and consumables need to be replaced using software analysis, Alan Sage, CEO of Digabit, told Design News.

Going forward, of course, the nature of the Internet of Things may make machinery even smarter. Its not far-fetched to imagine an industrial machine that senses when a part is becoming worn out and automatically ordering a replacement via an e-commerce portal, and scheduling its own maintenance, all without human intervention.

Riley said that while the desire for automated parts ordering capability based on predictive analytics isnt yet widespread, there are multiple companies in the M2M sensors and networking marketplace pursuing the endeavor. With the right network architecture, the sky is the limit in terms of what manufacturers can do with IoT technology.

[image via Software AG]

Article by Tracey Schematic (Contributing Writer) from Design News.

 

Scientist Creates AI Algorithm to Monitor Machinery Health

 

Photo

Dr. Rodrigo Teixeira’s patented algorithm adds artificial intelligence to machinery vibration analysis.

Topher Simon Photography

An artificial intelligence algorithm created by University of Alabama in
Huntsville (UAH) principal research scientist Dr. Rodrigo Teixeira greatly increases accuracy in diagnosing the health of complex mechanical systems.

“The ability to extract dependable and actionable information from the vibration of machines will allow businesses to keep their assets running for longer
while spending far less in maintenance. Also, the investment to get there will be just software,” says Dr. Teixeira, who is the technical lead for the
Health and Usage Monitoring Systems (HUMS) analytics project at UAH’s Reliability and Failure Analysis Laboratory (RFAL).

In blind tests using data coming from highly unpredictable and real-life situations, the algorithm consistently achieves over 90 percent accuracy, says Dr.
Teixeira.

If you can detect a fault before it becomes serious, then you can plan ahead and reduce the time machinery spends idle in the shop. As we all know, time is money.

Dr. Rodrigo Teixeira
RFAL principal research scientist

“This technology is in the trial stage. We are seeing how it performs in the field. If the results so far hold, we will build credibility and hopefully
gain acceptance with our Dept. of Defense partners,” he says. “At the same time, we are expanding our client base to include the private sector. There, we
believe we will have an even larger impact in the way they do business.”

Typical vibration analysis searches for anomalies in the vibration of machinery such as engines and gearboxes. These changes in vibration can signal wear
and future maintenance needs long before the machinery fails.

“Any machine shakes and vibrates, and it will vibrate a little differently when there is something wrong, like a fault,” says Dr. Teixeira. “If you can
detect a fault before it becomes serious, then you can plan ahead and reduce the time machinery spends idle in the shop. As we all know, time is money.”

The difficulty in extracting useful information from machinery vibration is the amount of random noise that exists in normal operating environments.
Finding that useful information has been a “needle-in-a-haystack” problem. Current monitoring algorithms assume that vibrations are static and that signal
and noise can be differentiated by frequency.

“The problem is that those assumptions never hold true in real life,” Dr. Teixeira says. “Instead, what we have done is to take an artificial intelligence
algorithm and ‘teach’ it the basic principles of physics that govern faults in a vibrating environment.”

Dr. Teixeira’s approach has provided the U.S. Army with a new way of producing actionable information from helicopter HUMS data, says Chris Sautter, RFAL
director for reliability.

“His approach, using machine learning, permits the analysis to look at the history of the data output rather than just a single flight. We train the
algorithm much like you train your cell phone to understand your voice,” Sautter says. “When the particular component we are monitoring sees vibration
signatures that no longer reflect the normal performance of a component, an alert is passed to the maintenance team.”

The RFAL algorithm fits easily into the Condition Based Maintenance paradigm that has been adopted across the Dept. of Defense and the commercial aviation
sector, Sautter says. “Having this capability and the ability to enhance the maintenance policy of large fleet operators has presented UAH and the
Reliability Lab with a host of new clients for our research capabilities.”

Article by Jim Steele (Research Writer) from the University of Alabama in Huntsville.

Will artificial intelligence be the future for monitoring machinery health in the Industrial sectors?

 


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.

Analysers

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.

 

All You Ever Wanted to Know About Online Protection Systems – Part 2

Panel Monitor Systems

As I mentioned in Part 1, a machinery vibration protection panel system comprises:

  1. Displacement probes (‘probes’) & coaxial cables (which connect to the proximitor)
  2. Proximitors (or ‘Drivers’ or ‘Oscillator / Demodulators’)
  3. Field Wiring – to / from the proximitors to the Zenner Barriers
  4. Zenner Barriers
  5. Rack (Housing) System
  6. Panel monitors
  7. Relays to installation DCS system – to provide external alarm annunciation or input to an automatic shutdown device.

The above items (1-3), are located in the “Hazardous Area”, whereas items (4-7) are installed in a “Safe Area”.

There are a number of different types of protection panel monitors, which can be installed within your rack system e.g.:

  • Dual channel radial probe monitors
  • Dual channel axial probe monitors
  • Multi-channel temperature monitors
  • Reciprocating compressor rod-drop monitors
  • Keyphasor monitors

However, in this article, and for the sake of brevity, reference will only be made to radial probe, axial probe and keyphasor probe monitors.

Rack Components

A typical protection panel system comprises the following items:

  • A Rack (or housing) – to accommodate the undernoted modules
  • A power supply – to provide power to the monitors in the rack
  • A system monitor
  • Vibration monitors – for displacement, velocity & acceleration
  • Keyphasor modules

The above are only a representative list of monitors that are available, and a range of other monitors/modules are available used for a range of different requirements.

The Rack

The rack, which is normally 19” (482.6 mm) is the part, which ‘houses’ the individual monitors. They have a backplane with multi-pin connectors attached for each individual monitor to connect to. Each rack must accommodate the Power Supply, System Monitor and various types of monitor. The images below show an old style Bently Nevada 7200 Series and 3300 Series monitor racks, with the newer style of rack shown below these 2 images.

Bentley Nevada 7200 Series Rack System

Bentley Nevada 7200 Series Rack System

Bently Nevada 3300 Rack System

Bently Nevada 3300 Rack System

Sensonics G3 Protection Rack System

Sensonics G3 Protection Rack System

 

The power supply

The power supply is itself powered from the platform or installation’s power supply system (i.e., a 240 V or 110 V ac supply, or a DC supply). This in turn, supplies power to each of the rack monitors and their associated transducers. It converts the input AC power into DC voltages used by the monitors installed in the rack. The power supply can provide either – 24 V dc or – 18 V dc voltages to each monitor for powering the attached transducers. The transducer voltages are overload protected, per channel, and on the individual monitor circuit boards. Each manufacturer stipulates where the power supply module must be located in the rack – either the first or last (depending on manufacturer) module – working from left-to-right.

The rear panel of a Sensonics G3 rack system is shown below, provides terminals for connecting the primary (input AC or DC) power, Rack Inhibit Control, Trip Multiply Control, Remote Alarm Reset control, and two keyphasor transducers, and connections for communications processor, optional serial interface for communications with PLC’s, SCADA systems and DCS systems, and includes terminals for OK relays.

Rear Panel Sensonics G3 Rack System

Rear Panel Sensonics G3 Rack System

The System Monitor

A system monitor can provide:

  • Alarm setpoint adjustment
  • Keyphasor power, termination, conditioning and distribution
  • Alarm acknowledgement
  • Control of the “OK” function
  • Buffered keyphasor output signals at the BNC connectors on the front panel.

Optionally, it can also provide:

  • Serial Data Interface (SDI) for communication of transducer and monitor data to process computers, digital / Distributed Control Systems (“DCS”). Programmable controllers and other control and automation systems.
  • Dynamic Data Interface (DDI) for communication of transducer and monitor data to compatible Bently Nevada machinery management software (e.g., System 1).
  • The ‘Trip Multiply’ function, which when activated, multiplies the selected monitor’s alarm setpoints by 2x or 3x (this is specified at the time of ordering). This is set for an individual monitor, so you can set which monitor(s) in the rack are to operate with the trip multiply function.

The OK function, mentioned above, indicates the correct operation of the system and associated transducers and field wiring. The system monitor drives the OK relay, which is located on the power input module. If a transducer or field wiring develops a fault, the OK relay will latch and a “Not OK” signal will be annunciated, and the relevant channel OK LED will flash.

The ‘Trip Multiply’ function, which when activated, multiplies the selected monitor’s alarm setpoints by 2x or 3x (this is specified at the time of ordering). This is set for an individual monitor, so you can set which monitor(s) in the rack are to operate with the trip multiply function.

  1. Trip Multiply – between a certain speed (rpm) range, at which there is a ‘critical’. However, when the machine is operating out with this rpm range, its normal alarm levels are in operation.
  2. Inhibit functionality can be used temporarily suppress all alarming. There are various types of inhibit functions. Some such as “Rack Inhibit” essentially disable all functions of the monitoring system – not just alarms. This essentially means ‘running blind’ with no indication of vibration levels whatsoever.
  3. Alarm Time Delays – this can be used to ensure that a channel must continuously be above its alarm setpoint for a pre-determined duration before the alarm will trigger. This option can be useful for machines, which pass very rapidly through a resonance.

The system monitor also must be installed in the rack in a specific rack position (working from   left-to-right).

Dual Channel Radial Probe Monitors

These monitors, depending on the manufacturer and model, may have a monitor meter, which will have two measurement scales: (a) a vibration amplitude scale – normally scaled in microns peak-to-Peak in the UK, and (b) a DC gap voltage scale – in negative volts DC.

This type of vibration monitor meter will either have a pair of analogue meter ‘needles’ (the old 7200 Series Monitors) or an LED bar graph (3300 System Monitors), to indicate each individual transducers overall level amplitude. The DC gap voltage is obtained by means of pressing a dipswitch, below the meter, on the front panel of the monitor. Later models – the current 3500 series system, does not have a direct monitor indication of vibration amplitude levels or of the associated gap voltages, but rely instead on a connected computer or built-in display screen to display the data.

Older Rack & Monitor Types

The older rack monitors have analog gauges with a set of switches and LED’s.

The Bently Nevada 7200 series monitors (see below) are an example of this earlier type of monitor and have a gauge at the top, various LED’s and three separate spring-loaded switches. Below the switches, are the “buffered Output” connectors (4 mm in this case). The ‘blue’ buffered output is for the “vertical” channel, whilst the ‘green’ one is for the “horizontal” channel. However, the transducers, which provide the signal to these buffered output connectors, may not in reality be truly mounted in the vertical or horizontal plane.

The top (centre) switch of these monitors is used to toggle between displaying, on the meter scale, the “Alert” and “Danger” setpoint values, which has been set up in the monitor. The ‘alert’ setpoint will be displayed by pushing the switch to the left, and conversely, by pushing this switch to the right, the ‘danger’ (or “trip”) setpoint values will be displayed on the meter scale. The danger setpoint, when exceeded, will simply stop the machine – hence the term ‘trip’.

The lower two switches are used to display, on the meter scale, either the dc gap voltage (switch pressed down), or the overall vibration amplitude, for the selected channel – switch pushed upwards. These 7200 series monitors normally display the overall vibration level, for the probe with the highest vibration amplitude, between the two vibration channels.

To obtain the DC Gap Voltage for a specific channel, the appropriate lower switch is pressed downwards (i.e., in the “GAP” direction), and the voltage for that probe is displayed on the “Black” (left) scale, by the red needle. To display a channel’s Overall Vibration Level, press the appropriate channel’s switch upwards (in the “VIB” direction), and the vibration level for that channel can be read on the “Red” vibration scale (on the right).

7200 Series Dual Probe Monitor

7200 Series Dual Probe Monitor

 

7200 Monitor Switches & LED

7200 Monitor Switches & LED

At the foot of each 7200 monitor, there are two 4 mm plug sockets (blue & green above), as previously mentioned, one for each probe channel, which are referred to as “Buffered Outputs”. Each buffered output is used to obtain vibration and gap voltage data from each of the probes, using for example, a portable vibration data collector and / or an analyser, such as an NI ‘Zonicbook’, Bently Nevada ‘ADRE’ unit or an HGL Dynamics.

Note: on the 7200 series monitors, one (Signal) red ‘Banana Plug’ should be connected to the appropriate probe channel buffered output socket, and the black (Common) banana plug should   be connected to the rack System Monitor’s “Common” (Black) 4 mm socket.

In contrast to the old Bently Nevada 7200 series monitor, their newer 3300 Series Dual Radial Probe monitor (which is shown overleaf), has a LED bar graph style indication of vibration and gap voltage levels on their meter scales.

Dual Channel Radial Probe Monitors

The 7200 series dual radial and axial probe meter scales are shown immediately below:

7200 Radial Meter

7200 Radial Meter

7200 Thrust Monitor Meter

7200 Thrust Monitor Meter

More Modern Generation Rack & Monitor Types

In the 3300 monitors – shown below, there two BNC ‘buffered output’ connectors, a DC Gap voltage toggle switch, and the two setpoint display switches on their front panel. These monitors, in contrast to the 7200 series ones, display both channels overall vibration levels simultaneously. Therefore the only switch, which would normally be required to be pressed, is the ‘gap’ switch, which displays each channel’s dc gap voltage in the centre scales.

3300 Dual Radial Probe Monitor

3300 Dual Radial Probe Monitor

3300 Monitor Front Panel

3300 Monitor Front Panel

As can be seen from the 3300 Dual Radial Probe Monitor  previously, each of the 3300 series monitor channel’s displays the overall level as an independent bar graph, with each probe’s amplitude level being indicated on the scale on the left and right side of the meter. The meter’s centre scale is used to display the gap voltage for both channels. By default, the 3300 series monitors normally display the overall vibration level for both channels (recall: the 7200 series monitors only display the level for the probe with the highest level – since these monitors only have a single vibration scale). However, in order to display the DC Gap Voltages on a 3300 series monitor, the dipswitch labelled “GAP”, which is located at the foot of the monitor’s front panel, should be depressed. A 3300 dual axial thrust probe meter scale is shown below.

7200 Dual Thrust Probe Monitor

7200 Dual Thrust Probe Monitor

3300 Dual Thrust Probe Monitor

3300 Dual Thrust Probe Monitor

3300 Monitor Scale

3300 Monitor Scale

In order to obtain the ‘Buffered Output Data’ from a 3300 series monitor, the data collector (or analyzer) should be connected to the BNC buffered output connectors at the foot of the  monitor’s front panel by a BNC-to-BNC cable. In the case of the 3500 monitors (as with the 3300 monitors), no other connections to the rack are required, in order to obtain the vibration and / or gap voltage data (with the exception of phase data – which is obtained from a separate keyphasor monitor).

These monitors (7200 & 3300 Dual Thrust Probe Monitors & 3300 Monitor Scale) mentioned earlier, have a different measurement meter scale to the radial probe monitors (Radial & Thrust Monitor Meters & 7200 & 3300 Dual Thrust Probe Monitors & 3300 Monitor Scale) – in that they have a ‘centre zero’ axial displacement scale.  Above the ‘zero’ mark on their scale, is the ‘positive’ or “Normal” section of the scale, and below the ‘zero’; is what is referred to as the ‘negative’ or “Counter” part of the scale.

These monitors are normally configured in such a way that the meter reading indicates a zero value when the shaft thrust collar is located mid way between the thrust bearings “active” and “inactive” bearing pads.

When the shaft is thrusting in its ‘normal’ thrust direction (i.e., towards the ‘active’ thrust pads), the displacement – usually scaled in mm (or in MIL’s), is shown as a ‘normal’ or positive value on the monitor’s meter. If, on the other hand, the shaft is thrusting towards the ‘inactive’ thrust bearing pads, it is said to be in the “counter” direction – or a negative direction, and the value is assigned in this case as a negative reading value.

Note: these monitor scales are normally marked in millimetres (mm) or MIL’s, since they  are measuring the physical distance (gap) between the probe tip and the shaft thrust collar,  and/or the end of the shaft.

Power Supply / System Monitor Module – Keyphasor Outputs

7200 Series Power Supply

7200 Series Power Supply

3300 System Monitor

3300 System Monitor

The 7200 Power Supply module is ‘powered’ from a 240 or 110 V ac power supply. This module in turn provides DC power to each of the rack monitors and their associated transducers. It also provides two other main functions:

  • A “common” ground (black) 4 mm socket connector – for ‘grounding’ the buffered output signals for the individual monitor channels (see 3300 System Monitor above).
  • Dual “keyphasor” buffered output signals – for the 7200 power supply, or four in the case of the 3300 system monitor.

In order to obtain the phase angle from this module, connect to the appropriate keyphasor connector (i.e., Kf 1 or Kf 2) and the centre (black) ‘common’ socket.

The 3300 System Monitor on the other hand, has four Keyphasor buffered BNC output connectors on the front panel. The front panel of this module also has two LED’s – one for  Supplies OK –, which is illuminated (green) when the supply voltage is within tolerance. The second LED indicates; when illuminated (green), that the Trip Multiply function is active.

Below the LED’s, there are two adjacent switches for adjusting the setpoint levels up or down. The bottom centre switch is a reset switch. This monitor also provides the power to the keyphasor transducers.

Keyphasor probes provide a once-per-turn voltage pulse – either a negative or positive pulse, depending on whether the keyphasor probe is sensing a notch feature such as a keyway (negative pulse) or a projection such as a key – giving a positive voltage pulse as previously described (see ‘Keyphasor Probes’ from Part 1).

3500 Series Keyphaser Module

3500 Series Keyphaser Module

Sensonics G3 Keyphaser Module

Sensonics G3 Keyphaser Module

In the case of the 3500 rack system, it has dedicated 2-channel keyphasor modules, which differs from its predecessors (the 7200 and 3300 systems), which in their case were located  in the power supply module and system monitor respectively.

The Rack Interface Module (RIM)

3500 Series RIM Module

3500 Series RIM Module

This module provides a means of setting up the rest of the rack monitors, has four status LED’s for: OK Relay, TX/RX, TM and Config OK. These LED’s indicate if the RIM is operating properly: (a) when it is communicating with other rack modules, (b) when in trip multiply mode, (c) when the module is communicating, (d) and that the rack has a valid configuration respectively.  Below the LED’s there is a rack ‘reset’ toggle switch.

The RIM module has a “Run / Program” key switch in the centre of the front panel, an address switch, and a D-Type (9-pin male) connector for rack / PC communications.

This module partially replaces the functionality of the system monitor in the 3300 series rack systems.

Modern Rack Systems

Current Generation Rack & Monitor Types:

The current protection system rack systems differ from their predecessors, in that they no longer have an analog meter mounted on their front panel. They may have a display, as shown below in the Sensonics G3 rack, or may be limited to only having a set of BNC buffered output connectors. [Note: the Sensonics has a set of SNB screw type buffered output connectors for each channel.]

Sensonics G3 Rack

Sensonics G3 Rack

Sensonics G3 Module

Sensonics G3 Module

The above monitor is a 4-channel monitor, in contrast to previous monitors, which were 2-channel monitors.  In addition, the above Sensonics G3 monitor can have each individual channel configured; through the configuration software, to be set up as any of the previous monitor channel types. This is because each channel has its own individual PCB, as shown below-left.

G3 4 Channel Protection Module

G3 4 Channel Protection Module

However, other manufacturers have 4-channel monitors, which are designed specifically for a particular function – see below the Bently Nevada 3500 series monitors.

Bently Nevada 3500 Series Monitor

Bently Nevada 3500 Series Monitor

The 3500 monitors, have 4 transducer channels connected to them, each of which should be identified on the card below the BNC buffered connectors. The four channels are labelled as Channel 1, to channel 4 – reading from top-to-bottom.

Another obvious difference between the 3500 series and the 7200/3300 series monitors, is that the panel of these 3500 series monitors only has a set of LED’s (“OK”,  “TX/RX” and “Bypass”) and the four BNC buffered output connectors.

The Bently Nevada 3500 System is their current system, whereas the 7200 series system is now termed “obsolete” by them and there are no parts available for these. The 3300 series racks are still currently in widespread use, but now with limited spares availability.

However, the 3500 series rack systems, in common with the 7200 and 3300 series racks, must have a power supply. But in the case of the 3500 series racks, they have a Rack Interface Module (“RIM”) instead of a system monitor. The Sensonics G3 rack has a “Comms Module”, which does the same thing.

The function of the RIM is to configure the rack monitors, and retrieve machine information. The RIM must be installed in “Slot 1” – which is the left-most slot position in the rack in the 3500 rack. A RIM monitor image is shown below.

RIM Monitor

RIM Monitor

In the case of the Sensonics G3 rack, the Power Supply and Comms monitor are both located at the left-end of the rack, as shown below.

Sensonics G3 Protection Rack System

Sensonics G3 Protection Rack System

 

What Everybody Ought to Know About the Transducer & CM Panel Systems – Part 1

Introduction:

I tend to split up machinery types into two main groups –

• Critical Machines
• Non-Critical machines

Critical machines are those which, if they fail in service, will have an impact on:

(a) Production

(b) Safety – both plant and personnel

(c) The High Capital Replacement cost

(d) Those machines which have an extended spare part(s) availability timescale, etc.

Machines which I have noted as “Non-Critical”, are used in this context to separate the (generally speaking) larger, higher capital cost, machines from the smaller ones. However, it must be stated that some of these so-called ‘non-critical’ machines may also have some degree criticality associated with them, but do not justify the high cost of installing an ‘on-line protection system’.

This course will discuss those larger, critical machines, which have an on-line protection system, and those which might have been upgraded beyond a ‘protection’ panel system, to a full ‘condition monitoring system’. A condition monitoring system comprises a protection panel system, but has the additional capability to store (and retrieve) your data, produce plots and reports. Pure protection systems, on the other hand, do not store any of your data.

A machinery protection system comprises:

1. A set of transducers – primarily non-contact displacement probe types
2. A “Proximitor” or “Driver” or “Oscillator / Demodulator” units
3. Field Wiring
4. Safety Barriers
5. A vibration panel system
6. In some cases, an attached computer for data storage, data analysis and reporting

The Transducer:

In order to have some type of measurement quantification and repeatability, an interface device must be provided between your operating machinery and the diagnostician. The devices used for this task are electronic sensors or the transducer. These transducers convert numerous types of mechanical behaviour into proportional electronic signals. The transducer outputs are usually converted into voltage sensitive signals that may be recorded and processed with various electronic instruments.

The industrial transducer used for measurement of dynamic characteristics typically falls into three distinct categories:

• Shaft sensing proximity (displacement) probes (or ‘Eddy Current’ Probes)
• Mechanical motion velocity coils
• Solid state piezoelectric devices (for measuring both velocity and acceleration)

There is no universal sensor that can be used for all measurements, on all machines, under all conditions. The electronic signals from the transducer is quantified in terms of the following parameters:

• Amplitude (i.e., magnitude or severity)
• Frequency (i.e., rate of occurrence)
• Timing (i.e., phase relationship)
• Shape (i.e., frequency content)
• Position (from proximity probes only)

Most protection systems comprise primarily of displacement probes; which are often also referred to as: (a) “Proximity Probes

(b) “Eddy Current Probes

(c) “Non Contact Probes”.

The transducer measures “relative” shaft vibration, which is generally expressed in terms of amplitude by a Peak-to-Peak amplitude value. As its name implies, this measurement extends from the lowest portion of the dynamic time signal (i.e., bottom peak) to the highest portion of the signal (i.e., the top peak). Shaft vibration measurements are quantified in units of microns (μm), or 1 x 10-6 metres. In Imperial measurement terms, it is in units of MILS (i.e., 0.001” or 1/1000th of an inch); and where:1 MIL = 25.4 μm; and 1 μm = 0.03937 MIL’s (or 0.03937”).

In the SI (metric) system, the amplitude is normally expressed in units of microns Peak-to-
Peak (μm Pk-Pk), and in the Imperial system, it is in MIL’s Peak-to-Peak (MIL Pk-Pk).

Shaft Displacement Probes:

This type of transducer measures relative displacement of rotating or reciprocating shaft surfaces. The word ‘relative’ refers to the vibration between the probe tip (i.e., the machine casings) and the shaft surface. These displacement probes are supplied in a number of sizes and configurations. They come in a range of tip diameters, mounting thread sizes, and mounting thread lengths, to suit your desired application. Typical tip diameters are: 5 mm, 8 mm, 16 mm and up to 2” diameter. However, the majority of the probe tip diameters are either 5 mm or 8 mm. The figure below shows a typical displacement probe.

Regardless of configuration, eddy current proximity probes consist of the same basic components, a threaded stainless steel body and a plastic protective tip. A flat wound coil, which is located close to the probe tip, is connected by two wires to a coaxial cable that runs between the probe and proximitor (or ‘Oscillator’ / ‘Demodulator’) unit.

This cable is in two parts:

(1) The integral probe cable – which is typically of the order of 0.5 metres long,

(2) An Extension cable. The two cables are connected by a miniature coaxial connector. These two cables must be electrically tuned to a specific length in order to maintain the proper impedance between the probe and the proximitor. If the interconnecting cable length is altered from the correct value, the transducer calibration will be influenced. In addition errors can occur if the shaft material and probe system are not matched. The ‘free end’ of the probe coaxial cable is connected to the proximitor by a miniature coaxial connector.

Transducer_Shaft Displacement Probe1

Transducer_Shaft Displacement Probe2

Proximitor (or ‘Oscillator’ / ‘Demodulator’):

Bently 7200 Series Proximitor

Fig 1. Bently 7200 Series Proximitor

Fig 2: Bently 3300 Series Proximitor

Fig 2: Bently 3300 Series Proximitor

The word “proximitor” is a copyright word and property of Bently Nevada, and refers to the unit into which all external wiring is terminated, and is normally mounted in a local junction box in the field, and close to the machine and associated probes. Each displacement probe has its own individual proximitor, or ‘driver’ or ‘oscillator / demodulator’ as it is sometimes also referred to as.
The proximitor contains an internal oscillator that converts some of the input energy into a radio frequency signal in the Megahertz range. This high frequency signal is directed to the probe coil at the tip of the probe, via the interconnecting coaxial cabling.

The flat pancake coil at the tip of the probe broadcasts this radio frequency signal into the surrounding area of the probe tip, as a magnetic field. If a conductive material (e.g., the shaft surface) intercepts the magnetic field, eddy currents are generated on the surface of that material, and power is therefore drained from the radio frequency signal.

As the conductive material approaches the probe tip, additional power is consumed by the eddy currents on the surface of the conductor. When the probe tip is in direct contact with the surface of the conductive material (e.g., the shaft surface), the majority of the power radiated by the probe tip is absorbed by the material. As the power loss varies, the output signal from the proximitor also exhibits a change in output voltage. In all cases, a small gap produces a small output signal voltage, and a large gap results in a large output voltage from the proximitor to the panel monitor. Non-conductive materials such as air, gas, fluid between the probe tip and the shaft surface have no effect on the signal.

On the other hand, surface scratches on the probe ‘target area’ does have a significant effect on the signal output, as does magnetic anomalies and other surface irregularities. These
Imperfections and irregularities give rise to output signal errors, known collectively as a
“glitch”.

 

 

Sensonics Proximitor with Coaxial Cable and Probe Assembly

The figure above shows a Sensonics Proximitor with Coaxial Cable and Probe Assembly.

Displacement Probe Calibration:

The relationship between distance (i.e., probe tip to shaft gap) and output voltage to the monitor is achieved by a combination of electronic circuits within the proximitor. For instance, a ‘demodulator’ removed the high frequency carrier signal, and a linearization circuitry provides a reasonably flat curve over a typical range of 80 to 100 MILs (0.080 to 0.100 inches = 2032 to 2540 μm). The probe sensitivity approximates a straight line in the form of :

y = mx + c – which is the linear part of the slope of the calibration curve, which can also checked from the calibration curve- i.e.,

                    Differential Static Gap Voltage (V dc)
Sensitivity = —————————————————- [mV / MIL]
                    Differential Static Probe Tip Gap (MILs)

However, to convert this sensitivity value in mV / MIL to mV / μm, simply divide the sensitivity in mV / Mil by 25.4 = 7.87 mV / μm [for a normal 200 mV / MIL system].

Note: Different shaft materials have a different sensitivity, therefore, the sensitivity value
must be considered in relation to the shaft material used.

The figure below shows the calibration curve for ANSI 4140 Steel, and the “sensitivity” is equal to the slope of the (relatively) straight line graph, and is equal to the value of “m” in the y = mx + c equation above (i.e., 196 mV/MIL). This graph however, is not a totally straight line, and ‘bends’ at the top right and lower left ends. (∴Assuming “C” {the y-axis intercept}= 0: then y = 196 • x + 0; e.g., y = 196 • 50 + 0 ==> so y = 9800 mV = 9.8 V)
Calibration Curve for ANSI 4140 Steel

Proximitor Field Wiring:

This “field wiring” refers to the wiring to the proximitor from the protection panel, which typically, is a fully shielded three conductor 18 AWG (American Wire Gauge – which is 0.0403” in diameter (1.02 mm) and has a cross-sectional area of 0.832 mm2) cable. The cable “shield” is normally grounded at the monitor rack, and the field end of the shield is allowed to ‘float’. This prevents ‘ground loops’ from developing in the transducer wiring.

Within the three wire cable, one wire is used for the output [vibration] signal (White) to the
monitor, the second wire provides a common ground (Black) and the third wire is the power input to the probe coil (red). A power input of typically – 24 V dc is applied to the proximitor from the associated panel monitor (or a regulated DC power supply). Normally, this cable length (for 18 AWG cable) is restricted to about 1000 feet (305 metres), for non- hazardous areas, and less for hazardous areas. This is to avoid a reduction in frequency response and high capacitive loads, particularly where hazardous areas are involved, which involve stricter conditions for capacitive loads.

Displacement Probe Output Signals:

The distance between the displacement probe tip and the shaft surface is (when the shaft is rotating), oscillating in a uniform manner. This type of repetitive motion is referred to as Simple Harmonic Motion (SHM), and it is convenient to describe with a sine wave. This oscillating motion is translated
by the probe calibration curve into an oscillating voltage. More specifically, this is commonly referred to as an alternating, or an AC voltage. This AC voltage is proportional to, and represents, the vibration displacement (time-domain) signal.

The probe also outputs a second signal, which is proportional to the static gap between the probe tip and the shaft surface, and is referred to as the “Gap Voltage” or DC voltage. This is also called the “DC Offset”. The maximum DC voltage is coincident with the peak gap distance. Similarly, the minimum output DC voltage matches the point of the closest gap. The average distance between the probe tip and the ‘target’ (i.e., the shaft surface), is referred to as the Average Shaft Position.
Thus, the AC output voltage is proportional to vibration, and the DC output voltage indicates the average distance of the oscillating target with respect to the stationary probe tip. The figure below shows the average DC output gap voltage (the vertical line from the ‘x-axis’) with the AC (vibration signal) voltage superimposed on the DC Offset voltage.

Probe Calibration Curve

Keyphasor Probes:

Another application of proximity probes is to provide a timing signal. Typically these are synchronous, once-per-revolution pulses that may be used for accurate speed measurements. They are also employed for phase measurements and determination of precession, when combined with other probes on the machinery train. These 1x timing pulses are typically referred to as “Keyphasor” signals, and the transducers which provide these signals are called “Keyphasor Probes”. These probes are often positioned over a shaft notch (i.e., a keyway) or a drilled hole. With this arrangement, the probes produce a negative going pulse as the shaft indentation passes under the timing probe. In some cases, a raised surface such as the top of a shaft key is observed, giving a positive going pulse. The keyphasor signal should have a pulse height of between 5 an 15 Volts. The necessity for a strong and
consistent keyphasor signal cannot be overstated. Thus these probes only provide a dc gap voltage pulse, dependent on whether it is a keyway or shaft projection which triggers the keyphasor pulse. The image shown below, shows the effect of a “notch” (e.g., a keyway) in the shaft surface [Fig 6-5], or a “projection” (e.g., a key) on the shaft surface [Fig 6-6].

Negative & Positive Trigger Pulse Signal & Associated Blank Bright Sequence

The radial, axial and keyphasor probes are combined in many different combinations. In most instances, a pair of mutually perpendicular radial probes are installed at each journal bearing (X-Y Probes). A pair of axial probes are typically mounted at each thrust bearing, and a radial keyphasor probe will usually be installed for each shaft speed.

Barrier Protection:

A large portion of plant in the Oil & Gas industry (and also in other industries) is located in a ‘Hazardous Area’, which requires the use of “IS” equipment and systems. Intrinsically Safe (IS) equipment is defined as:

Equipment and wiring which is incapable of releasing sufficient electrical or thermal energy under normal or abnormal conditions to cause ignition of a specific hazardous atmospheric mixture in its most easily ignited concentration”.

In this context, this is achieved by limiting the amount of power available to electrical equipment in the hazardous area to a level below that which will ignite the gases.
Protection panel systems require power to be sent out of or into a hazardous area. This is achieved by installing Zenner Barriers, which are located in a “Safe Area”.

These barriers are passive devices, which are used to safely divert excess electrical energy to ground, to ensure that the maximum energy possible at the terminals in the hazardous area fall far below the explosive point of any volatile gasses present.

Field wiring is connected to/from these diode devices, thus limiting the power supplied to the proximitors and displacement probes, which are located in a hazardous area, and also the power returning from the probe and proximitor to the protection system panel monitors. These barriers can be installed externally in the cubicle which houses the protection panel rack, alternatively, they can be installed internally within the panel rack system.

Note: There is always a voltage drop across these Zenner Barriers. Therefore the voltage output measured at the probe / proximitor will not be the same as that measured at the
monitor input terminals.

Do you have any questions so far ?

Stay tuned for Part 2.

If you found this post useful, I’d be very grateful if you’d help it spread by sharing it via the buttons below. Thank you!

 

7 More Reasons Why You Need the Sentry G3 Sensor Condition Monitoring System for Your Power Plant – Part 2

The Sentry G3, high performance sensor conditioning monitoring system is used for a wide range of functions in the Power Plant Industry, these include; shaft position, high / low pressure cylinder expansion, turbine block expansion, shaft vibration and eccentricity speed.

Applications

The turbine block expansion can measure the expansion of the turbine block relative to the floor, specifically temperature from 55 to 65°C, pressure from 15 to 20 kg sq/cm, vibration from 18 to 20 um and also oil vapour detection. For shaft vibration and eccentricity, the sensor monitors speeds from 3 to 300rpm when the turbine was started, with a unit of measuring um (10-6 m).

Finally, there is a speed sensor covering the range of 0-4000 rpm (turbine rated speed of 3000rpm) with 2 alarms for over-speed of 10% and 16% in comparison with the rated speed.

With the above applications in mind, please find below 7 more key features of the Sentry G3 and how these can benefit your Power Plant and outperform any other sensor conditioning and monitoring system on the market:

  1. G3 Module Comms Independent  If the comms from one module becomes compromised it will not affect the rest of the system, thus reducing the risk of total system down time and loss of production.
  2. 3U High Rack  The 3U/24 channel max rack allows for smaller installations. This is more space efficient in crowded control cabinets (especially important if retrofitting to an existing system). Hence, it saves money as unused channels need not be purchased and more likely to be able to install the G3 in an existing cabinet.Competitor systems use 6U as standard.
  3. Live Colour Display  There is a local colour display with live data displays, alarm history, FFT and trend data etc. This enables the operator to view and interrogate data at the unit. This in turn, increases operator efficiency, especially if data storage/condition monitoring software is located away from machinery.
  4. UK Manufactured and Supported  Speedy response to orders/telephone technical enquires/on-site engineer requirements – increases potential system up time due to reduced response times (and therefore increased production), also typically less expensive than sending engineers to the UK from around the world.
  5. Modbus RS485 and Ethernet ConnectionDual Redundant Power Supplies (per rack)  Industry standard connectivity to plant systems – usually configured and managed by customer ensuring reduced labour costs, delivery times and increasing up time as typically managed in-house.
  6. Dual Redundant Power Supplies (per rack)  Industry standard configuration ensures maximum system up time.
  7. Independent Alarms – High Integrity  There are alarm relay and analogue output facilities independent from other module facilities, thus suitable for IEC61508 applications e.g. SIL-3 over speed protection. This further adds to the flexibility of the system, one module/DSP card type can then be used for a variety of machinery monitoring purposes.The over speed is system typically supplied with 2 out of 3 voting modules too.

To learn more about this exciting and cost effective product, please contact us or learn more

 

 

MMS Introduce the Laser Doppler Vibrometer

MMS are pleased to introduce the HGL Dynamics Single Point Laser Doppler Vibrometer (LDV) and Scanning Laser Doppler Vibrometer (SLDV) to their inventory of products.

These relatively new products aim to help machinery engineers, help solve complex rotating equipment problems. Learn more about the Laser Doppler Vibrometer

Do You Make These Mistakes in Condition Monitoring?

The Problems with Condition Monitoring

For condition monitoring, to be a ‘success’ as a maintenance strategy, assumes that the equipment is monitored on a frequent and regular basis; typically once-per-month. However, the reality is often that it is considered less important than other tasks assigned to maintenance staff.

In the case of the offshore Oil & Gas industry, bed space, helicopter seat allocation and conflicting priorities, conspire against the CM work being carried out regularly. It is not seen as a positive and beneficial activity, rather it is viewed as a problem, which will be fitted in where and when possible, given the above restrictions. Management commitment and support however, is often the main missing element for CM to work; they perceive it as a cost, rather than a benefit.

The other element which is often overlooked is that CM is only appropriate for certain types of equipment and failure modes, in which a reasonable time exists between detection of the failure and its ultimate failure. This is illustrated below in the “P-F Curves”. This P_F interval is the time from the point (P) – the potential failure point, to the functional failure point (F).

What are the main problems that you face with your type of equipment?

Condition Monitoring_Potential Failure Curve 1

P-F Curve

 

Condition Monitoring_Potential Failure Curve 2

P-F Curve…Detailed Analysis

 

Condition Monitoring_Potential Failure Curve 3

P-F Curve…More Detailed Analysis!

An example of a functional failure (F) is when a car engine seizes due to a lack of oil, and the car stops. The potential failure (P) is when, say, a pump impellor is worn, but still pumps the fluid, but not operating at the required performance (i.e., flow rate) level required. Note that ‘failure’ in this context does not necessarily mean the equipment is physically damaged, but rather it may only mean that it is not performing or functioning to the required or specified level.

Therefore, if the P-F interval is short and the CM measurement interval is relatively long, there is a high probability of a failure occurring. Similarly, if the P-F interval for a particular failure mode is say 6 weeks, and the CM measurement task is only implemented either (a) infrequently or (b) every two months for example, then again, an undetected failure is likely to occur.

 The Benefits of Condition Monitoring

Condition Monitoring, if correctly applied, and given the essential management support and commitment, can save money. Most company accountants regard the maintenance budgets as another overhead on the operating cost. Certainly, CM equipment, software, computers and training all cost money in order to implement CM, but the benefits far outweigh the costs.

Savings which can arise from the implementation of CM:

  1. A reduction in spares holding – only order spare parts when required
  2. A reduction in breakdown failures
  3. A time interval to plan a shutdown for repairs on equipment
  4. A reduced cost for warehousing spare parts inventory
  5. Only replacing parts when their condition dictates this should be done
  6. Because this method employs a range of non-invasive techniques, and no invasive actions are required, there is also a reduction in human intervention factors, which contribute to increased costs [Recall the old saying: “If it isn’t broke, don’t fix it”]

Machinery failures do not follow any specific and predictable failure pattern unfortunately, but are subject to:

  • how well maintained the equipment is
  • Is the equipment being operated within its design parameters
  • Is the equipment being subjected to high and cyclic stresses
  • Is the machine being operated in a hostile environment

All of the above factors can affect the life of a machine and its components, making time-based or preventive maintenance strategy risky, as well as costly. The above points are therefore, perhaps, the most compelling argument in favour of employing CM, where appropriate, as a part of the maintenance strategy in a plant.

What exactly do you do to make your plant more reliable in terms of operation?

 Maintenance Strategies

There are three maintenance strategies commonly employed, and these are:

  • Breakdown (or Run-to-Failure)
  • Time-based (or Preventive)
  • Condition Monitoring (or Predictive)

The Breakdown maintenance strategy is a traditional method where machines are simply run until they fail in service. This in principle gives the longest time between shutdowns, but failure, when it does occur, can be catastrophic and result in severe consequential damage – which is often referred to as secondary damage. This can therefore lead to an increase in repair times and may eventually impact on production. There is still a case for breakdown maintenance, in situations where there are large numbers of small machines, where the loss of one machine has no impact on safety and production. Failure can also include economic failure or performance degradation to a point considered to be where the equipment is no longer providing an acceptable level of performance for its task.

Preventive maintenance is where the plant management decides, and takes some actions, based on a fixed time or operating hour interval, to carry out maintenance tasks, which are deemed to be shorter than the expected time between failures. However, It does mean that the vast majority of machines will run longer by a factor of two or three. The advantage of this method is that most maintenance can be planned well in advance and that catastrophic failure is greatly reduced. The disadvantages, in addition to the fact that a small number of unforeseen failures ca still occur, are that too much maintenance is carried out and an excessive amount of perfectly usable parts are replaced. There is also the possibility of introducing faults, which would otherwise not happen, due to wrong part replacements, incorrect installation, poor workmanship etc.

This method is still widely applied, particularly where statutory regulations require inspections on a regular basis – e.g., pressure vessels, lifeboats etc.

Condition based or Predictive maintenance is a diagnostic testing method, whereby the potential for breakdown of a machine is predicted through the monitoring and trending of a parameter or parameters, to enable maintenance to be carried out at the optimum time, as a result of regular measurements or assessment of plant condition.

Do you require any help with condition monitoring issues?  We would love to assist you…

Contact Machinery Monitoring Solutions today, for help defining your condition monitoring needs or to schedule a demonstration of our products.

 

Exactly What is Condition Monitoring?

Put more succinctly, Condition Monitoring (or “CM”) is the process of monitoring a parameter (or parameters) which reflect the condition or performance of a piece of equipment, in order to identify any significant degradation, which is indicative of a developing fault, or an unacceptable drop in equipment performance.

The key word is ‘monitoring’ in the context of condition monitoring. This conditional monitoring task requires regular checks of the selected key parameters, which have been selected, to be in a position to identify the onset of a failure or drop in performance. Then subsequently schedule the appropriate maintenance intervention, in a timely manner, to prevent failure and avoid its consequences. CM, which is a non-invasive technique, which is usually employed on rotating equipment such as: pumps, compressors, fans, turbines and electric motors etc. The ultimate aim of condition monitoring is to only perform maintenance work only when necessary.

The most common technique used in condition monitoring is vibration analysis, where measurements are taken on machine bearing housings with transducers – which are normally accelerometers, in triaxial directions, as shown below. This system employs portable battery-powered instruments called data collectors/analysers; this methodology is referred to as an “offline” system, using instruments such as the Adash A4900 VA4 Pro 4-channel unit below.

Condition Monitoring_Vibration Analysis 1

Accelerometer

Condition Monitoring_Vibration Analysis 2

Adash A4900 VA4 Pro 4-channel unit

However, on more critical machines, eddy-current displacement transducers are used, which directly observe the rotating shafts to measure the radial and axial displacement of the shaft as shown below. These displacement transducers are permanently mounted on the machine housings, and monitor the condition of the machine on 24/7 basis, and is known as an “On-Line” system.

Condition Monitoring_Eddy Current Displacement Transducer

Eddy Current Displacement Transducer

 

Condition Monitoring_On-Line System

Machine Shaft

The signals from these eddy current ‘prox probes’ are fed back to a permanently installed rack system, such as the Sensonics G3 system below, which is designed to protect these high capital investment and production critical machines from failure.

Condition Monitoring_Permantly Installed Rack System

Sensonics G3 System

 

Other Condition Monitoring Techniques

There are other condition monitoring techniques to consider, and machines may have one or more of these applied, depending on its criticality and likely modes of degradation and the cost of failure. These other CM techniques (in addition to vibration analysis) include:

  • Spectrographic Lube Oil Analysis
  • Ferrography
  • Thermography
  • Acoustics
  • Performance analysis

Lube oil analysis is perhaps the next most widely employed CM technique after vibration analysis, and perhaps, more increasingly, thermography and performance analysis.

When you call it a day on the plant, is your mind more at ease thanks to condition monitoring?

We would love to hear your feedback…

7 Reasons Why You Need the Sentry G3 Sensor Condition Monitoring System for Your Power Plant – Part 1

Sensonics Sentry G3 Monitoring and Protection System

Sensonics Sentry G3 Monitoring and Protection System…For all your Condition Monitoring needs!

 

The Sentry G3, high performance machinery protection and condition monitoring system is used for a wide range of functions in the Power Plant Industry, these include; shaft position, high / low pressure, cylinder expansion, turbine block expansion, shaft vibration, eccentricity, and speed. 

Applications

The Sentry G3 system is capable of monitoring a number of variants. For example, shaft position measuring and monitoring, relative to the position between the machine shaft and the journal or hydrodynamic bearing surface. The system also automatically protects the critical machines in your plant when the relative position is over the pre-set level. Specifically, the machine train will be stopped when the shaft moves within the bearing clearance towards say towards the generator side of a turbo generator set, by an excessive amount, such as, for example 1.2mm or when the shaft moves to the turbine side by 1.7mm (-1.7mm to + 1,2mm). Other variants include; axial thrust position, high and low pressure cylinder expansion, a variety of process data; such as bearing temperatures, pressures and flow rates, with each requiring an alarm signal.

With the above applications in mind, please find below 7 key features of the Sentry G3 and how these can benefit your Power Plant and outperform any other machinery protection and condition monitoring system on the market:

1.  Sentry G3 Programmable Modules

The Sentry G3 contains modules and plug/play DSP channel cards. Hence, there is no requirement to decide measurement type (abs vib, rel vib, disp, temp, process) prior to purchase.  Meaning, the customer can purchase the exact monitoring unit as required i.e. 1, 2, 3 or 4 channels per module of any machinery monitoring type without unused spare channels. This in turn saves costs and increases flexibility as channels can be simply added by the customer in future as required.

Competitor systems require purchase of complete modules e.g. all four 4 channels, rather than the required number of relative vibration channels actually needed per module.

With programmable modules, this is also advantageous, as the customer can hold spare stock of ‘blank’ G3 modules and DSP cards/channels. Having the blank units in stock means the customer will not have to wait for spares delivery from the manufacturer (which can be between 4 – 6 weeks from a major competitor) in the event of the replacements being required.  Also, a reduced spares inventory can be held as all modules and DSP cards can be configured individually by the customer for any measurement mode.  It must be noted that holding stock of specific and dedicated modules is expensive.

Finally, with the programmable modules, these can readily be upgraded by the customer (using simple freeware, standard laptop/USB), as programming of modules/DSP cards is a simple process.  This of course helps reduced costs (equipment supplier engineer rarely required) and reduced project time as the in-house engineer can perform this tasks as opposed to waiting for a 3rd party/equipment manufacturer engineer, to carry out this task.

Competitor systems often require an engineer to be sent to site for this and carry out modifications via dipswitches etc.

2.  Programmable Alarms (Warning and Danger Levels)

These ensure the system can be adjusted to meet specific customer requirements and not those specified by other industries. These types of protection systems are typically designed for the power industry, but are equally applicable for other industries.

3.  Low Pass Filter, HPF, Tracking and Notch Filters

As above, this ensures the system can be adjusted to meet specific customer requirements and not those specified by other industries.

4.  Independent Channel/DSP Cards

Should one DSP card/channel fail then this will not affect other channels within the module or wider system.  This reduces the risk of overall system downtime and blank DSP cards can be held in stock locally for immediate replacement.  Competitor systems will require a complete module swap should a channel go down.

Sensonics Sentry G3 Universal Machinery Protection Monitor

Sensonics Sentry G3 Universal Machinery Protection Monitor…For all your Condition Monitoring needs!

5.   API670 Compliant

The customer is assured the G3 will work with industry standard sensors and to the required overall specifications. This gives the customer confidence in the equipment performance and also reduces costs in a retrofit e.g. where existing sensors are required to be connected to the protection system.

Competitor systems often require an engineer to be sent to site for this and modifications via dipswitches etc.

6.  Open Source Data Output 

The G3 will communicate with other open source software packages (typically via buffered outputs on rack rear panel) used for data analysis, storage and condition monitoring. This increases customer choice, thus potentially reducing costs.  It also enables the customer to continue with their preferred analysis software (if open source type).

A certain competitor is now going down the route of using proprietary data comms. Hence, the customer will be locked in to that competitor’s hardware/software if they go down this route…

7.  G3 Module Power Independent

The G3 modules are powered independently; therefore if one module fails others will not be compromised. Hot swaps of modules can be performed, reducing service times and reducing risk of total system down time and therefore loss of production.

To learn more about this exciting and cost effective product, please click here