Vibration Monitoring in Manufacturers of Pharmaceuticals

Table of Contents

Introduction
Vibration Monitoring in Action
Taking Advantage of Vibration Monitoring
A Closer Look at Vibration Sensors
Inside the Air Handling Unit
Specification and Installation

Introduction

Accurate data capture is critical as part of a predictive maintenance plan in pharmaceutical manufacturing. Hansford Sensor’s believe that modern vibration monitoring techniques and technology can maximize performance.

Vibration monitoring has been used for almost two thousand years with the oldest vibration sensor known to historians was a seismograph invented by Chinese astronomer Chang Heng in the second century AD. This device was able to respond to distant disturbances by depositing a bronze ball from the mouth of one of eight dragons placed at intervals around a large urn, therefore indicating the direction of a distant earthquake and potentially saving lives by enabling the government to send assistance to the affected area.

Today’s vibration monitoring systems are no longer sculpted in the forms of mythical beasts. This is because the development of vibration monitoring has been less concerned with visual impact and more concerned with enhancing performance. The users of each application in which vibration sensors are used, demand higher productivity from each mechanical system. Therefore, there has been a corresponding growth in the need for sophisticated vibration sensors that maximize the performance of many engineering processes.

In recent times, designers and engineers of vibration sensors have not only succeeded in providing devices of exceptional reliability but also in packaging that functionality in a variety of resilient and extremely compact enclosures to enable its use within a wide range of applications.

Vibration Monitoring in Action

Vibration sensors are used widely in pharmaceutical manufacturing. An example of this is air control, a method of manufacturing medicine that is probably older than even vibration monitoring, although the drying of animal flesh and bone to produce powdered drugs no longer represent the height of pharmaceutical technology.

Successful and effective air handling in the pharmaceutical sector requires machinery that can stabilize air conditions within precise limits during the manufacturing process, with no sudden changes to air flow rate, temperature or humidity. To ensure that these levels are carefully managed, machinery must be correctly specified, maintained and run. A mechanical failure will make a degradation in air standards almost inevitable, with the potential for lost production, the risk of penalties from late orders and the danger of customer dissatisfaction.

Taking Advantage of Vibration Monitoring

Vibration monitoring systems aid engineers protect air handling units from unexpected failure. Ensuring this comes down to several key factors. These include installing accelerometers correctly; gathering and analyzing data properly; and taking the necessary action, though is should be noted that in some cases, the best course of action may be ‘no action’.

Condition monitoring has become increasingly commonplace in industry and as a result, training in the use of components such as vibration sensors is now provided by organizations such as BINDT (British Institute of Non-Destructive Testing). This is important because, vibration sensors offer high levels of performance and reliability, but the component is only as good as its installer. Because of this, when mounting a sensor there may be a choice between drilling, tapping or gluing; but engineers need to understand and consider how these methods may affect the warranties on their equipment. It should be known that, with the right advice and assistance, the rotating elements of air handling units can be cost-effectively monitored to enable vibration engineers pick up early signs of any degradation in the equipment, so that maintenance can be planned and carried out with minimal expense and disruption to service.

A Closer Look at Vibration Sensors

An accelerometer includes a piezoelectric crystal element that is bonded to a mass. The mass compresses the crystal when subjected to an accelerative force, and this causes the crystal to produce an electrical signal that is proportional to the force applied. This is then amplified and conditioned by inbuilt electronics to produce a signal that can be used by higher level data acquisition or control systems either online or offline.

The online system measures and analyses the output from sensors and interfaces directly with a PLC. On the other hand, an offline system is created by mounting sensors onto machinery and connecting them to a switch box; engineers can then use a hand-held data collector to collect readings.

The two main categories of the accelerometer are AC accelerometers, which are typically used with data collectors for monitoring the condition of higher value assets such as critical process systems, and 4-20 mA accelerometers, which are commonly used with PLCs to measure lower value assets, like motors, fans, and pumps. AC versions offer the additional capability to detect gear defects, belt problems, looseness, and cavitation, but both AC and 4-20 mA accelerometers can identify misalignment, bearing condition and imbalance.

Inside the Air Handling Unit

A typical air handling unit contains a supply fan and an extractor fan, coils that circulate steam or hot water for heating, chilled water for cooling and air filters, encased within a large metal enclosure with removable panels. The complete fan and motor assembly are confined within the enclosure, so engineers can easily gain access to carry out any necessary maintenance procedures by removing the panels. It should be known that the supply fan and extractor fan can either be direct-drive or non-direct drive. While the direct-drive fans may require a vibration sensor on both the drive end and non-drive-end bearing, the non-direct drive fans may require the addition of two accelerometers on the journal bearings of the gear shaft.

The established and cost-effective technique for identifying imbalance and misalignment in air handling units employs 4-20 mA sensors mounted onto bearings and shafts, with the velocity readings being fed back to a PLC, allowing overall vibration trends to be monitored. Both a 4-20 mA output and an AC output can be provided by a dual output sensor, allowing engineers to take in-depth vibration analyses via a data collector.

An M12 connector used in conjunction with separate M12 cable assemblies offers an effective option in an air handling unit, as the M12 connector is of a smaller size than many alternatives, and the associated cable assemblies have a tight bend radius.

Furthermore, another option is to use fixed AC sensors hard-wired to switch boxes outside the air handling unit, allowing data to be collected safely from the same positions on a regular basis. The limitation of this choice is that readings only apply to the moment in time that they were taken.

Specification and Installation

Stainless steel units are often compulsory in pharmaceutical applications when it comes to switch boxes. important guidance on installation will be given by an established supplier who will also offer valuable advice on specification issues.

The preferred mounting technique is to drill and tap a thread directly onto the machine so that an accelerometer with an integral ¼-28UNF, M6 or M8 mounting thread can be screwed into place. This so called ‘drill and tap’ method can also be used to fix a mounting stud, to which an accelerometer can then be attached. There are specialized installation kits are available for this task.

It is vital that the right tools are used for the job, as tightening the sensor outside the appropriate torque levels can damage equipment or reduce its effectiveness. Overtightening can damage the sensor by stripping the thread. Similarly, under-tightening will lead to inaccurate readings due to poor contact with the vibrating surface.

However, if drilling and tapping is not an option, the next best thing is to attach mounting studs using adhesive. Consideration of the temperature present within the application must be taken and there should be careful choice of an adhesive that is capable of coping with that temperature. Applications at temperatures up to 100 °C, a metal-filled epoxy adhesive would be the appropriate substance to use.

In addition to this, having installed accelerometers as carefully as possible, ensure that the accelerometer cable is clamped to the body of the accelerometer itself with cable ties. This will prevent strain and the false readings that can be generated when loose cables create excessive movement.

The specification and installation issues must be carefully considered as this will ensure that the air handling unit will be able to maintain air control consistently to the benefit of the plant as a whole, but it may also be possible to extend the operating life of equipment beyond recommended maintenance intervals – guarding against the expense generated when increases in vibration lead to machine failure, downtime and unwelcome reductions in production volume or quality.

This information has been sourced, reviewed and adapted from materials provided by Hansford Sensors Ltd.

For more information on this source, please visit Hansford Sensors Ltd.

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