Coal & Quarry Industries

Dependable vibration monitoring

Within the Coal & Quarry industries, it is common for machinery to be running around the clock so the rotating parts of the machinery (for example, motors, gearboxes, pump, screens, crushers, conveyors) need to be continuously monitored to warn of bearing and component wear. As these machines are frequently installed in areas which are difficult to access and with high costs incurred when there are any failures, it is vital to be able to pre-determine potential problems so corrective action can be taken.

Over the years the type of machinery that can be found in the Coal & Quarry industries has seen great success with condition monitoring. The technique of vibration monitoring has been accepted and proven as a highly cost effective method. Typical modes of failure that can be detected include bearings, misalignment of shafts and out of balance fans. If these problems are not detected early, there can be disastrous consequences such as machine downtime, which is not only extremely costly but could also cause injuries. 

Hansford Sensors has approached this market with various products dependent on the end user and OEM requirements, and has supplied many thousands of industrial accelerometers worldwide to mines.

ATEX certified solutions

Within this industry there may be instances where the sensors are used in potentially explosive gas atmospheres, for example, an underground coal mine. This means any products used in this environment must be ATEX (IECEx) certified for an intrinsically safe area, in this case specifically Group I (mining).

Within the mining sector it is common to monitor conveyors that are running under 60Hz. In these situations a higher sensitivity sensor, for example, 500 mV/g (HS-100 Series) can improve the signal to noise ratio and increase the capability of conducting a full data analysis. If 4-20mA vibration sensors (HS-420 Series) are installed with the signal being interfaced with a PLC (programmable logic controller) or similar system, Hansford Sensors would recommend a 0-25 mm/s RMS velocity sensor (HS-420 Series). This is a great method for monitoring ‘out of balance’ on fans. A 0-2g RMS acceleration 4-20 mA sensor (HS-422 Series) is good for providing protection on conveyors in between routine surveys.

Whether the sensors are to be installed on a crusher, screen, conveyor pulley or drive, Hansford Sensors would recommend a side-entry/low profile model. If conditions permit, top-entry can be used, but the location of the sensors may need to be reviewed to ensure debris (for example, coal falling from a conveyor) cannot damage the sensor. Some mining environments are suitable for installing top-entry sensors, for example a pump room. In these areas Hansford Sensors would advise using top-entry unit for a more cost effective solution.

Mining is one of the harshest environments where sensors are installed so Hansford Sensors would recommend using armoured/braided cable as it has less chance of potential damage.

Hansford Sensors advise using 2 Pin MS connector sensors with separate IP66 2 Pin MS cable assemblies so if an urgent shutdown is needed, it is much easier and quicker to remove rather than dismount the whole sensor.  In installations where there is a strong possibility of the cables being damaged, this method would require replacement of only the cable assembly rather than the sensor. This has to be weighed up with the initial cost advantage integral cable units have over units where a separate cable assembly needs to be purchased. The minimum IP rating for mining should be IP65 and for where assets are submersed, IP68 units should be used.

Regardless of whether the application is an online or offline project, there are a family of stainless steel enclosures available for connecting the accelerometer cables. For offline, a local switch or connection box (HS-SE/CE) is recommended providing the facility for the data collector to be connected. If the application is for an online system, local stainless steel enclosures are available. With the experience that Hansford Sensors has in the market, there are also some custom-built products that have been designed for the harsh conditions. These include special enclosures with fabricated roofs to provide protection.

HS-500 Series for maximum control of conveyors and screens

A comprehensive family of vibration modules (HS-500 Series) has been customised to suit applications in coal handing and quarry areas where vibration conveyors/screens are needed to be controlled.

To get the best results the sensor should be mounted as close to the bearing as possible, in a stiff area of the housing (for example, not on motor covers). It is also important to ensure mounting options are suitable for the environment and installation techniques to guarantee the best readings are obtained. Loose mounting or bad surface preparation will give rise to resonance or loss of high frequency data. The use of magnetic mounts or spikes may reduce the high frequency signals, but this is unlikely to cause a significant problem when trending data. The cable should be clamped to the body of the sensor with a cable tie to prevent strain and excessive movement of the cable as both these could produce false signals. The cable should also be fixed at suitable intervals to cable trays or other suitable supports.

Hansford Sensors Ltd has a wealth of experience in the design and manufacturing of industrial vibration sensors for various applications and can offer technical advice on specific applications. For further advice please consult our technical team on +44 (0) 845 680 1957 or email sales@hansfordsensors.com.