Vibration Monitoring in the Cement Industry
Vibration Monitoring to Boost Efficiency
In this article Chris Hansford, Managing Director of Hansford Sensors, explains how predictive maintenance, in particular vibration monitoring, helps to maximise the efficiency of machinery used in cement manufacturing by reducing downtime to a minimum. It includes advice on how to specify and install suitable solutions.
The Harsh Environment of Cement Manufacturing
Cement manufacturing is one of the most aggressive of all production processes. The chemicals used to produce Portland and Masonry cement, particularly silicates, aluminates and aluminoferrites, combine to create high levels of fine particles that cause significant problems for production and handling equipment.
Rotating components are at greatest risk and are commonly found in motors, pumps and fans used in crushers, mills, precipitators, kilns and silos.
Although equipment with moving parts is usually fitted with protective covers or sealed to high IP standards, it is impossible to prevent the ingress of fine particles, typically between 15 and 45 microns in size. This affects lubricant efficiency, increases wear on bearings, shafts and seals, and raises the risk of premature failure, especially in high temperature areas.
How Vibration Reveals Mechanical Wear
Worn rotating parts increase internal tolerances, causing mechanical imbalance, loose components and rubbing parts. These issues manifest as vibration, which can be detected by appropriate sensors.
Because vibration sensors can detect very low vibration levels and small changes between vibration states, it is possible to assess wear rates and take corrective action before faults develop.
Boosting Efficiency in a Growing Market
The cement market is growing rapidly, and the most efficient producers are best positioned to capitalise on this growth.
World cement volumes were forecast to grow at a compound annual growth rate of 4.9 percent to 2017, with per capita consumption increasing significantly. Other industry analysts predict continued growth at around 4 percent annually.
To operate profitably in such a competitive and cost sensitive market, suppliers must ensure maximum reliability under demanding conditions. Many cement plants operate below capacity due in part to maintenance time.
Optimising existing systems through vibration monitoring can significantly reduce maintenance time and increase productivity.
The Role of Vibration Monitoring
Vibration monitoring equipment was originally developed to help industrial manufacturing and process industries improve productivity and profitability.
In recent years, the industry has shifted from reactive maintenance to predictive long term maintenance strategies. These approaches are often applied process wide and aim to maximise uptime while reducing operating costs. Vibration sensors are a critical element in this strategy.
How Vibration Sensors Work
Vibration sensors, also known as accelerometers, contain a piezoelectric crystal bonded to a mass. When subjected to vibration, the mass compresses the crystal, producing an electrical signal proportional to the applied force.
This signal is amplified and conditioned to create a measurable output suitable for data acquisition or control systems.
Data from accelerometers mounted in key locations can be collected using handheld data collectors or routed via switch boxes to centralised systems for continuous monitoring.
Key Assets to Monitor in Cement Manufacturing
In cement plants, key components to monitor include motors and gearbox assemblies in kiln drives, crushers, screens, conveyor belts, raw mills, elevators, separators and blowers.
Correct sensor selection is critical for reliable operation, ease of installation and accurate data collection. In some applications, side entry sensors may be preferred to prevent debris damage. In high temperature areas, appropriately protected sensors should be used.
Specifying and Installing Accelerometers
To specify an accelerometer correctly, engineers must consider vibration levels, frequency ranges, environmental conditions such as temperature, and the presence of corrosive chemicals.
Additional considerations include whether the atmosphere is combustible and whether there are weight constraints.
Working closely with the sensor supplier ensures correct performance. Hansford Sensors offers a wide range of vibration sensors designed to withstand the harsh conditions of cement manufacturing, with multiple connection, output and environmental options.
Importance of Correct Installation
Accelerometers are only as effective as their installation. Poor installation or maintenance compromises precision and longevity.
Condition monitoring depends on stability. A poorly mounted accelerometer may produce readings that reflect sensor instability rather than changes in machine condition.
Modern accelerometers operate over wide temperature ranges and offer high accuracy with low hysteresis. Stainless steel housings prevent the ingress of contaminants.
Accelerometers should be mounted directly onto machines on flat, smooth, unpainted surfaces that are larger than the sensor base, free of grease and oil, as close as possible to the vibration source and perpendicular to the axis of rotation.
Mounting Methods and Measurement Directions
Correct sensor installation is essential to detect imbalance, misalignment, bearing defects, mechanical looseness, hydraulic forces and rubbing.
For horizontal measurement, sensors should be mounted on motor or pump bearings to detect imbalance and foundation issues.
For vertical measurement, sensors should be mounted on drive end bearings to detect looseness and structural problems.
For axial measurement, sensors should be mounted on drive end bearings to detect misalignment.
Depending on criticality and budget, additional sensors may be installed, though motors and gearboxes remain the most important components to monitor.
Typical Sensor Placement Examples
On a typical crusher motor, accelerometers are mounted radially on the drive end and non drive end to monitor bearing condition.
On gearboxes, sensors are mounted radially on input and output shafts to monitor bearings and fan imbalance, with optional axial sensors to monitor thrust.
Cement plants typically use 4 to 20 milliamp accelerometers connected to PLC systems via local junction boxes and multicore screened twisted pair cable for data trending and alarms.
Data Collection and Analysis
Offline vibration monitoring is performed using portable data collectors, either with temporary sensors or handheld devices connected to permanently installed sensors.
Maintenance teams develop data collection routes based on equipment criticality to maximise efficiency.
Increasingly, sensors are hard wired to centralised control systems for real time monitoring, which is more efficient and safer, though more expensive.
Regardless of data capture method, it is essential to analyse appropriate frequency spans based on the fastest rotating components to avoid misinterpretation.
Using Vibration Data to Improve Reliability
Careful data analysis can reveal issues such as misaligned bearings, loose components, dry couplings or dust build up causing imbalance.
Vibration monitoring alerts engineers to problems before further damage occurs, even when the root cause is unexpected.
Summary: Top Tips
Identify the vibration level and frequency range
This is the first step before selecting a vibration monitoring system. Temperature and humidity must also be considered.
Consider the working environment
Cement manufacturing is highly demanding. Sensors must be sealed to high levels and withstand high temperatures and corrosive chemicals.
Online or offline monitoring
Online systems interface directly with PLCs. Offline systems rely on handheld data collectors.
Install close to the vibration source
Accelerometers should be mounted as close as possible to the source of vibration.
Establish a monitoring network
A dedicated network of sensors improves efficiency and prevents failures.
Maximise stability
Stable mounting is essential. Consider drilling, tapping or gluing methods carefully.
Train operators
Training reduces human error. Organisations such as the British Institute of Non Destructive Testing provide appropriate training.
Use vibration data effectively
Ignoring warnings risks costly failures. Early maintenance is always preferable.
Consult an expert
Professional advice is essential. Working with an experienced supplier such as Hansford Sensors ensures the best specification.
