Vibration Monitoring for Pharmaceutical Manufacturers
Introduction
Accurate data capture is essential as part of a predictive maintenance plan in today’s pharmaceutical manufacturing. Modern vibration monitoring techniques and technology can be used to maximise performance.
Vibration Monitoring: Tried and Tested Technology
Vibration monitoring has been employed for some time now and has been in use for almost two thousand years. The oldest vibration sensor known to historians was a seismograph invented by Chinese astronomer Chang Heng in the second century AD.
This device responded to distant disturbances by depositing a bronze ball from the mouth of one of eight dragons placed around a large urn, indicating the direction of a distant earthquake and potentially saving lives.
Vibration monitoring is one of the oldest solutions in the engineering workplace, with a lineage that outstrips other technologies by centuries. Today’s vibration monitoring systems focus less on visual impact and more on performance.
The increasing demand for productivity has driven the need for sophisticated vibration sensors that maximise the performance of engineering processes. Modern sensors offer exceptional reliability and are packaged in resilient, compact enclosures suitable for a wide range of applications.
Vibration Monitoring in Action
Vibration sensors are used widely in pharmaceutical manufacturing.
Air control is a method of manufacturing medicine that is older than vibration monitoring itself, although early processes no longer represent modern pharmaceutical standards.
Today, effective air handling requires machinery capable of maintaining precise air flow, temperature, and humidity conditions during manufacturing. Mechanical failure can lead to degraded air standards, lost production, penalties from late orders, and customer dissatisfaction.
Taking Advantage of Vibration Monitoring
Vibration monitoring systems help engineers protect air handling units from unexpected failure.
Key factors include installing accelerometers correctly, gathering and analysing data properly, and taking appropriate action. In some cases, the correct response may be no action.
As condition monitoring has become more common, training in vibration sensor use is provided by organisations such as the British Institute of Non Destructive Testing.
Even high performance sensors are only as effective as their installation. Engineers must understand mounting methods such as drilling, tapping, or gluing and how these may affect warranties.
With appropriate guidance, rotating elements of air handling units can be monitored cost effectively, enabling early detection of degradation and planned maintenance with minimal disruption.
A Closer Look at Vibration Sensors
An accelerometer contains a piezoelectric crystal element bonded to a mass. When subjected to an accelerative force, the mass compresses the crystal, producing an electrical signal proportional to the applied force.
This output is amplified and conditioned by inbuilt electronics to produce a signal suitable for higher level data acquisition or control systems.
An online system measures and analyses sensor output interfacing directly with a PLC.
An offline system mounts sensors on machinery and connects them to a switch box, allowing engineers to collect readings using a hand held data collector.
Types of Accelerometers Used
There are two main categories of accelerometer.
AC accelerometers are typically used with data collectors for monitoring higher value assets such as critical process systems.
4 to 20 milliamp accelerometers are commonly used with PLCs to measure lower value assets such as motors, fans, and pumps.
Both types can identify misalignment, bearing condition, and imbalance. AC accelerometers also detect gear defects, belt problems, looseness, and cavitation.
Inside the Air Handling Unit
A typical air handling unit comprises a supply fan, extractor fan, heating and cooling coils, air filters, and a large metal enclosure with removable panels.
Fan and motor assemblies are enclosed, allowing engineers access for maintenance.
Direct drive fans may require vibration sensors on both drive end and non drive end bearings. Non direct drive fans may require additional accelerometers on the journal bearings of the gear shaft.
Monitoring Techniques for Air Handling Units
A cost effective technique for identifying imbalance and misalignment uses 4 to 20 milliamp sensors mounted on bearings and shafts.
Velocity readings are fed back to a PLC, allowing overall vibration trends to be monitored.
Dual output sensors can provide both 4 to 20 milliamp and AC outputs, enabling in depth vibration analysis via a data collector.
M12 connectors with separate cable assemblies provide a compact and effective option for air handling units.
Another option is fixed AC sensors hard wired to switch boxes outside the unit, allowing data to be collected from the same positions consistently.
Specification and Installation
Stainless steel switch boxes are often compulsory in pharmaceutical applications.
Accelerometers should be mounted directly onto the machine surface, which must be flat, smooth, unpainted, free from grease and oil, and larger than the sensor base.
Sensors should be positioned as close as possible to the vibration source.
The preferred mounting method is to drill and tap a thread directly into the machine, allowing accelerometers with integral mounting threads to be screwed into place.
Mounting studs may also be used. Specialised installation kits are available for drilling, tapping, and spot facing.
Care must be taken to tighten sensors within recommended torque levels. Over tightening can damage sensors, while under tightening leads to inaccurate readings.
If drilling and tapping is not possible, adhesive mounting may be used, with adhesive selection based on operating temperature.
Cable Management and Long Term Reliability
Accelerometer cables should be clamped to the sensor body using cable ties to prevent strain and false readings caused by cable movement.
Correct specification and installation allow air handling units to maintain consistent air control and may extend operating life beyond recommended maintenance intervals.
This reduces the risk of vibration related failures, downtime, and reductions in production volume or quality.
