A petroleum storage depot in Essex providing essential fuel supplies to various outlets across East Anglia needed some updating of its condition monitoring system; predictive maintenance system specialists, Sensonics Ltd were called in to update the facilities and to retrofit an improved vibration detection system.

When it was commissioned in 1991, the plant’s main line pump and motor station was provided with just one channel of vibration on the pump allowing only limited fault detection capability. With throughput on the pumps running at approximately 180m3/hour, any unforeseen breakdown whilst never representing a danger, could have resulted in a long shut down of the plant, a complete cut-off of fuel and a very expensive bill.

The station, situated on a hill top site is exposed and open to the elements and so Sensonics fitted four PZS3 type industrial accelerometers to replace the existing single channel system. Sensonics PZS3 accelerometers are of dual case stainless steel construction and being fully welded are sealed to IP.66/IP.67. and can be installed in minutes allowing for both durability and ease of installation; the instruments fitted were also ATEX approved intrinsically safe, suitable for use in hazardous Classified Zone 1 applications.

To provide optimum machine protection, one accelerometer was mounted on each end of the pump and on each end of the motor, these were complemented by the existing motor winding temperature measurements.

These latest shear-mode accelerometers with an even broader frequency band now operate on the site on a 24hour basis often in harsh environmental conditions. All the Sensonics instruments have a high reliability factor and contain no moving parts, which makes them virtually maintenance free and vibration is detected when the accelerometer is shaken back and forth in its sensitive plain, generating an electrical output proportional to the distress level in the pump or motor.

Sensonics additionally installed an Aegis Modular Machine Condition Monitoring System in the site’s control room. This comprised of MO9601 single channel vibration modules together with MO9605 single channel temperature modules, both fitted with A1 (Danger), A2 (Alert) alarms; the system also incorporated a M09699 display module.

Controls housed in a robust cabinet provide total machinery protection and prevent costly false alarms or the need for ongoing operator intervention. A1, A2 level alarms are clearly displayed by red LED’s.

The MO9601 vibration module is additionally capable of accepting inputs from velocity transducers or eddy current probes whilst the MO9605 temperature module will accept inputs from RTD’s. Display facilities on the MO9699 feature a high visibility 3½” digit LED display, a calibration check facility and remote alarm attenuation.

Fuel to the pumping station is received from a refinery in the Thames Estuary after being pumped underground over a distance of approximately 57 miles.

The Sensonics system was used in anger within days of the installation: an alarm shut the plant down after detecting a problem on the drive end of the motor. Further investigation revealed that a bearing was in need of lubrication. Had this not have been detected then it is highly probable that a bearing failure would have occurred. Particularly sobering was the fact that the old system would not have detected the malfunction and the plant could have faced shut down for as long as a month.

The Sensonics installation provides a greater level of protection than that previously in place and a supporting programme to ensure fast spare parts provision when and if required. Project Engineer for the plant, Alan Black said “the installation was cost-effective, uncomplicated, straightforward and completed on time. Both the work and the service provided by Sensonics were excellent and we were especially impressed when the system picked up the bearing problem almost immediately. We had previously used Sensonics equipment more prevalently than any other supplier throughout our national pipeline network and this early detection of a fault reaffirmed our confidence in them”.

Sensonics manufacture and supply monitoring instrumentation for predictive maintenance systems on a world-wide basis and are supported by a network of agents around the world. Full details are available on http://www.sensonics.co.uk/