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 Applications
The problem is that it only goes wrong during the night, and then only once or twice a week. Either we stay up all night, possibly for several nights or….. we use the Birdie-FTR. Connect all the control signals, contactor signals, motor and pump power feeds to the FTR, switch on and leave in logging mode. 3 days later, the fault happened again. Retrieve the FTR and replay the results. All three days operation is available to look at. Find the events that were logged around 4.00 that morning and…. The signal from the auxiliary contacts on the pump contactor is missing! This prevents the main burner circuit starting, hence no heat. Obviously, the auxiliary contacts have become intermittent and the contactor needs to be replaced… problem solved. This single incident would certainly have more than paid for the cost of the FTR. Our railways now have many 1,000s of unmanned level crossings which use automatic barriers to protect the track when a train approaches. The control systems are designed for maximum reliability and fail safe operation (for obvious reasons). As with all control systems, they are dependant on the correct operation of sensors and other external control signals. One particular crossing failed to open after a train had passed on several occasions, causing considerable delay and frustration to the road traffic. The fault was intermittent and by the time an electrician had arrived on site, the crossing was working correctly. The control unit was replaced on two occasions, but the problem persisted. An FTR was installed to monitor the various inputs and outputs and after 11 days, the problem occurred again. Studying the records showed that all the control systems were working properly, and the problem must be associated with the lifting motor. This was exchanged and the problem was cured. Subsequent investigation showed that an intermittent poor connection was present on one of the field windings. The vibration of a second passing train would be enough to restore the connection, clearing the fault before it could be investigated.
Using a conventional data logger was not an option because the signals varied from 12v dc to 240v ac and included 24v ac and dc, plus 110v ac. One of the advantages of the FTR is that it will accept this full range of voltages on any input, without any configuration hassles. Connecting the FTR and allowing the machine to run at normal speed until the fault occurred enabled the exact sequence of events that led up to the problem to be studied in detail. In particular, the order in which signals changed could be analysed, one step at a time. This showed that a momentary pulse from a proximity sensor was initiating an operation before its proper time. This occurred only when the machine was running at its normal speed due to centrifugal forces acting on a cantilevered mounting plate. Checking the operation of the sensor showed that its threshold adjustment had slipped. This gave an occasional false pulse only when the machine was running at full speed. Two minutes work with a trimmer and all was well. Each time the fault occurred, typically some 30 units would have to be manually reworked, at a cost of about £13 each. The FTR repaid itself by saving just two occurrences of this problem!
The captain of a rig support vessel reported that he had experienced momentary rogue operation of a rear thruster unit. These are used when manoeuvring in dock or in close proximity to a gas rig. Inadvertent operation could have very serious and potentially disastrous consequences. Initial thoughts were that the problem must lie with the thruster control rack, down at the rear of the engine room. An FTR was connected so that the control signals to the thruster control rack and the power feeds to the thruster were monitored. After 3 weeks another ‘glitch’ was reported. The FTR records were studied for the period when the fault occurred and it was seen that the problem was not with the thrusters or the local control rack, but in the signals coming down from the bridge. Subsequent investigations showed that interference from one of the radio transmitters on the bridge and poor ground bonding had caused the false signals to be generated.
Staff at a high security establishment wanted to run a monitoring programme to record the number of times doors were opened/shut over an extended time period. Statistical information related to door opening sequences was also required. The doors, of which there were 27, were controlled and monitored from a central office and it was therefore a simple matter to install two FTRs to cover the whole requirement. Every week, the data was downloaded to a PC and, using the FTR software, converted to a text file for export to a standard spreadsheet (Excel). It was then a simple matter to build the required analysis functions in the spreadsheet to provide the desired information. Complicated
Electrical Systems- Sorted
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LAPLACE INSTRUMENTS
LTD |
Tel: + 44 (0)1692
402070 Fax: + 44 (0)1692 404910 E-mail:tech@laplace.co.uk |
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Modified
December 5, 2013
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IRDIE-FTR