The following catalogue details the instrumentation and procedures which Keynes Controls utilise for condition monitoring applications. The catalogue is currently based upon the use of the NetPod 4000 and NDACS 5000 series instruments.

Not only do Keynes Controls supply systems to solve local problems but also the company’s systems offer true network data synchronisation enabling large scale applications to be created. Instruments can also be supplied to operate in hazardous and underwater environments.

Keynes Controls systems offer high resolution, high dynamic range and opto-isolation as standard. For many applications sensors can be directly connected to the instruments, no matter how they arrange distributed around a plant, without any additional precautions to be taken into consideration.

The 4000 and 5000 series instruments contain sample rate following filters to remove out of band noise ensuring that the sensor signals under investigation are accurately measured and features of interest are clearly identified.

Current Monitoring

Induction motors are used in industry for driving a vast range of machinery. The best maintenance strategy for motors depends largely on their size. For large motors the benefits of condition monitoring are hard to ignore. The motor is a fairly simple rotating machine and many of the vibration monitoring techniques described below can be used to diagnose bearing faults, balancing problems and coupling problems. A far more comprehensive indication of the motors electrical and mechanical condition can be obtained by monitoring the current passing through it.

Depending upon the strength of the magnetic fields and physical size of the motor then various current probes can be fitted. The most common being a clamp on current sensor. The output of the current sensor can be connected directly to the motor ammeter circuit if available. The signal can be analysed using Fourier Transform techniques and it is possible using this type of advanced analysis to identify the following defects:

·	Broken rotor bars

·	Cracked rotor end-rings

·	High resistance joints in squirrel-cage windings

·	Casting porosites in aluminium die-cast rotors

·	Poor brazed joints in copper fabricated rotors

·	Rotor winding problems in slip-ring induction motors

·	Static & dynamic air-gap irregularities

·	Unbalanced magnetic forces

·	Mechanical unbalance

·	Bent shafts

·	Bearing irregularities

The NetPod 4000 instruments can be fitted with a range of current interface modules that can be used to undertake the above analysis tasks:

Part Numbers: NPAI24-SC1 NPAI24-SC5A
NPAI16-SC1 NPAI16-SC4A

NetPod 4000 Condition Monitoring System Fig 1

Figure 1 above shows a typical installation for the NetPod 4000 system deployed for condition monitoring applications. The picture clearly shows how the instruments are deployed around a plant and connected to a range of sensors.

Figure 2 shows the inside of a pump test system plant. The NetPod 4000 instruments are distributed on a local network enabling engineers to run different test applications to local computers as well as to run standard condition monitoring applications for continuous monitoring operations.

NetPod 4000 installation in a pump monitoring station Fig 2