Pumps get testing time!

23/08/2012

Having for many years used one of Sensor Technology’s novel TorqSense non-contact torque sensors as an aid to product development, Watson-Marlow Pumps Group, the world’s leading specialist in peristaltic pumping, has now chosen another of these versatile and dependable sensors for production-line testing of its most critical products.

The TorqSense sensor was selected for this demanding application because of its ease of use and because of the reliability and accuracy that has been consistently demonstrated by the similar unit in use in the development department.

Widely accepted as the world’s fastest growing pump type, peristaltic pumps such as those manufactured by Watson-Marlow have no valves, seals or glands to wear, leak or replace. The fluid contacts only the bore of the hose or tube, thus eliminating the risk of the pump contaminating the fluid, or the fluid contaminating the pump.

Peristaltic pumps have a number of advantages over other pump types: they provide superior flow rate stability, accuracy to +/-0.5%; they are ideal for viscous and abrasive fluids as well as sterile processes; have extensive chemical compatibility; and are inherently hygienic and safe to run. In all, they offer the lowest whole life cost of all pump types.

Many of Watson-Marlow’s pumps are used as components in medical and pharmaceutical equipment and, in these demanding applications, accurate information about the operating characteristics of individual pumps is often needed. To meet the needs of its customers with applications of this type, Watson-Marlow offers the option of supplying products that are 100% tested prior to despatch.

A key element of the testing is the determination of the relationship between the operating torque of the pump and the flow rate it delivers. In order to be able to measure this, a torque sensor that will deliver accurate and reliable results over long periods without adjustment or maintenance is needed. These requirements, the engineers at Watson-Marlow Pumps knew, could most conveniently be met by using a sensor from the Sensor Technology TorqSense range.

These innovative sensors, which are covered by patents, are built around surface acoustic wave (SAW) transducer, which essentially comprise a pattern of interlocking conductive fingers deposited on a piezoelectric substrate, such as quartz.

This arrangement behaves as if it were a conventional resonant circuit with a resonant frequency in the radio frequency range. When the transducer is deformed, however, the resonant frequency changes. In torque sensing applications, the transducer is fixed to the shaft in which it is required to measure the torque. As the shaft twists in response to the applied torque, it deforms the transducer. By measuring the change in resonant frequency of the transducer produced by this deformation, the torque in the shaft can be accurately determined.

Since the SAW transducers operate at radio frequencies, it is easy to couple signals to them wirelessly. Hence, the TorqSense sensors that incorporate the SAW transducer technology can be used on rotating shafts, and can provide data continuously without the need for the inherently unreliable brushes and slip rings that are often found in traditional torque measurement systems.

In the latest application at Watson-Marlow Pumps, a TorqSense sensor with a nominal maximum torque rating of 0.5 Nm is used in a production-line test rig for peristaltic pumps where it typically measures torque over the range 0.11 to 0.17 Nm while the pump drive shaft is rotating at 60 rpm. The results are displayed and recorded using a netbook PC. The test results are ultimately logged against a serial number for every pump so that, in the event of a query from the end user, the test data for the pump in question can be readily located.

“As we had anticipated, the sensor was easy to install and set up,” said Harvey Crook of Watson-Marlow Pumps, “and it’s also very easy to use on a day-to-day basis. We’ve been using it for a considerable time now, and it has proved to be totally reliable, just like its larger counterpart in our development department. Our experience shows that these innovative sensors are a convenient, versatile and cost-effective choice for both development and production line applications.”


Putting feeling into drugs safety and handling

08/06/2011

Most applications we cover on the Read-out Signpost have to do with the actual production of product, say in a pharmaceutical process. However the products eventually end up in the hands of health professionals or patients and the correct handling of these in this area can be as important as in the earlier period of production. This application is one designed to help at this user interface.

When product integrity is paramount, packaging has a key role to play. It has to be secure enough for protection in all likely scenarios, but has to be easy to open in possibly high tension situations.

When using diagnostic fluids on ill or nervous patients, hospital staff are likely to be feeling the stress and will not take kindly to bottle tops that proves difficult to open. However they will want them to feel secure enough that they can be confident of the fluid’s sterility.

To this end specialist capping machines have been developed by Cap Coder, which not only tighten bottle caps within precisely defined tolerance but also log every detail of every bottle that is capped by one of their machines. And they have done it with a minimum of fuss, using an off-the-shelf technology and associated software.

“Our machines are essentially simple,” says Roger Brown of Cap Coder. “Filled bottles are presented to a torque head, which quickly screws on a cap. But the devil is in the details.

“A batch size is typically 10,000 bottles, which we have to cap at say one per second. Every cap has to be done up to the same torque, and we have to provide proof of this performance. Sterility has to be ensured – the machine may even be working in a high vacuum to ensure that no bacteria or other contaminants are present.

“Put all of this together and you end up with a need for a highly engineered machine.”

As the need for traceability emerged, Cap Coder realised that it would have to develop a standard solution, which while not quite identical for every machine, would be based on the same technology deployed in the same way. And because exports are the lifeblood of such an OEM, flexibility to meet different counties’ standards had to be designed in from the outset.

Even the largest bottle tops are not that big, so handling them at the speeds required can appear impossibly fiddly.

“Our philosophy is to have a simply machine design that avoids extraneous parts,” says Roger. “This lead us to the idea that we’d like the torque sensor to be wireless.”

Looking at torque sensors available on the market, one, TorqSense from Sensor Technology, stood out as meeting all criteria: simplicity, robustness, high speed and wireless. The company was contacted and design meetings set up.

Mark Ingham of Sensor Technology takes up the story: “Basically we could use TorqSense ‘as is’ for this application; we just needed to work out mounting arrangements. Similarly, the associated software was ready to go after a bit of calibration and some front end graphics.”

The sensors that attracted the attention of Cap Coder depend for their operation on surface acoustic wave (SAW) transducers. These transducers comprise two thin metal electrodes, in the form of interlocking “fingers”, on a piezoelectric substrate such as quartz. When an RF signal of the correct frequency is applied to the transducer, surface acoustic waves are set up, and the transducer behaves as a resonant circuit.

The key feature, however, is that if the substrate is deformed, the resonant frequency changes. When the transducer is attached to a motor drive shaft, the deformation of the substrate and hence the change in resonant frequency is related to the torque applied to the shaft. In other words, the transducer, in effect, becomes a frequency-dependent strain gauge.

Since the transducers operate at radio frequencies, it is easy to couple signals to them wirelessly. Hence, TorqSense sensors that incorporate the SAW transducer technology can be used on rotating shafts, and can provide data continuously without the need for the inherently unreliable brushes and slip rings that are often found in traditional torque measurement systems.

With the Cap Coder project, software was required to do two things: run the torque up to 10kgcm within tolerances of 10 percent, and record the actual value achieved. This secures the cap to the bottle at a level of tightness that will ensure security and sterility, yet is at a level that can be opened relatively easily by an adult. The logged values are saved to a hard drive to provide a permanent record for traceability purposes.

Roger explains: “Diagnostic fluids are distributed widely, typically to every hospital in the country, where they may be stored for months before use. Tracing each bottle’s origin would be practically impossible without full records being automatically produced and saved to a central location.

“We found a solution to this complex but critical problem using an out of the box technology. And what amazes me is the diversity of other fields in which TorqSense is used – its really any machine with a rotating shaft.”


Addicted to technology transfer

09/10/2010

By Tony Ingham

Technology transfer may prove one of the cornerstone engines for growth as Britain and other countries emerge from recession over the coming months. Tony Ingham of Sensor Technology  tells us his company is virtually addicted to the habit, so we asked him to tell us how it has shaped the company’s development and what the future holds.

TorqSense in Technology Transfer

Wireless became one of the buzzwords of the late Noughties, and ‘wireless’ got our grandparents’ generation excited too in the 1940s. But between those periods the word was not much used – except at Sensor Technology around the turn of the Millennium.

We’d identified a way to measure the torque in a rotating shaft without maintaining physical contact – well, the theory of how to do it! Doing away with the traditional slip rings would be a big advantage in many potential applications, and we kept thinking of more and more reasons to develop the concept.

Sensor Technology had been founded in the 1970s to develop various instruments and by the 1990s had diversified into several parallel fields of research and development. We had a number of projects running relating to electromagnetic corruption, EMC, and its control.

Computers and electronics were getting everywhere in the 1990s, but they could be susceptible to electrical interference if they were used in proximity to virtually any sort of machine. This included the obvious places like factory floors, but also hospital wards, offices, broadcast studios, shops full of refrigerators and police command centres. EMC was a big hurdle that had to be overcome if computers were to reach their full potential. We were working hard in the field, as were many other organisations.

Sensor Technology had been investigating the use of Surface Acoustic Waves (SAWs) or Rayleigh Waves as a way of blocking interference. These waves are produced by most objects in motion and the theory was that they could be made to interact with the EMC waves and cancel them out.  It’s a technique that several teams were working on and with which some success has been achieved.

We were setting up a long running trial on a lab bench. Things had got a bit messy and we were just tidying up a bit before starting the trial, when we noticed on our instruments that SAWs react to strain.

It was hardly a eureka moment, but over the next few days the idea grew that the SAWs could be refined to act as gauges. Even this didn’t get us too excited, but then it struck us that it was a wireless connection and this opened up many practical possibilities.

A few weeks and several late nights on and we had a workable proposition. Soon we had DTi (Department of Trade & Industry) and PERA (Production Engineering Research Association) backing to run a proof of concept project. This was successful and the race was on to develop a marketable product.

We protected ourselves with patents and worked out a plan to commercialise the technology. We needed a spread of application projects to work on; some easy, some tough; some commercial, some academic; some mainstream, some specialist. Fortunately, just about every machine in the world uses a rotating shaft to transmit power so there were plenty of contenders.

Universities were fertile grounds. At University College Dublin (IRL) the technology – by now dubbed TorqSense – was used to mix solids into liquids. It doesn’t sound that demanding, but there were highly defined targets relating to achieving an even mix in minimum time and with minimum power expenditure.

I could see that there were hundreds of industrial applications for this work, but I didn’t predict what it actually turned out to be – stirring meat and other ingredients into curry sauce on an industrial scale! This may sound a bit trivial, but it represents many many industrial processes, particularly in Ireland’s food-focussed economy.

The University of Greenwich (GB) provided a project at the toughest end of the scale – monitoring the torque in high speed rotating stone saws. These need to be brought up to speed very quickly; when they first contact the stone the shock load is incredible, but to get a smooth cut surface a constant torque has to be maintained throughout the entire cutting process, with on-the-fly adjustments being made to account for variations in the stone’s density.

Industrial stone cutting is a harsh environment and the TorqSense has to perform faultlessly for hour after hour.

The technology proved itself again and again in fields as diverse as aerospace, marine, nuclear, pharmaceuticals, packaging, pumping, conveying and mixing. Soon the company shifted its focus to developing variations of the basic theme.

We designed big and small units; single-piece sensors that are simple to fit; two-part units with a small head that will fit into the tiniest space and communicate to a controller elsewhere on the machine; a pulley replacement unit for direct installation on belt and chain drives, etc , etc, etc.

Another technology transfer is now underway. We are developing a load sensor, which is being built into helicopter cargo hooks. A wireless connection feeds real time data through to the pilot, and also logs it for later management analysis.

The wireless-ness is a massive advantage, because it means the hook is legally not a part of the aircraft. Therefore users don’t need to spend time and money getting Aviation Authority approval for its installation. The datalogging means exact billing to customers, while an integral GPS means spraying or similar tasks can be done with utter precision.

The commercial flying community is very excited about the idea and coming up with more and more avenues for us to explore.

This all seems a long way from the drive shafts and industrial plant we usually deal with, but it’s a not-unusual technology transfer scenario. We come up with an idea, get something working and let people see it. Chances are someone will step out of left field and say: “That’s just what I’ve been looking for.”


• There are other applications for Sensor Technologies’ TorqSense described on the Read-out Instrument Signpost’s other blog. Use the Google Search on the left hand column with the word TorqSense

 


“Once more with feeling!” Pharma capping reliability!

30/04/2010

Total traceability extends to packaging as well as product in the rarefied world of pharmaceuticals. Capcoder Ltd has adopted a novel torque sensing system as the core of the datalogging capabilities of its bottle sealing machines.

When product integrity is paramount, packaging has a key role to play. It has to be secure enough for protection in all likely scenarios, but has to be easy to open in possibly high tension situations.

When using diagnostic fluids on ill or nervous patients, hospital staff are likely to be feeling the stress and will not take kindly to bottle tops that proves difficult to open. However they will want them to feel secure enough that they can be confident of the fluid’s sterility.

To this end specialist capping machines have been developed by Capcoder of Oxford (GB), which not only tighten bottle caps within precisely defined tolerance but also log every detail of every bottle that is capped by one of their machines. And they have done it with a minimum of fuss, using an off-the-shelf technology and associated software.

“Our machines are essentially simple,” says Roger Brown of Capcoder. “Filled bottles are presented to a torque head, which quickly screws on a cap. But the devil is in the details.

“A batch size is typically 10,000 bottles, which we have to cap at say one per second. Every cap has to be done up to the same torque, and we have to provide proof of this performance. Sterility has to be ensured – the machine may even be working in a high vacuum to ensure that no bacteria or other contaminants are present.

“Put all of this together and you end up with a need for a highly engineered machine.”

As the need for traceability emerged, Capcoder realised that it would have to develop a standard solution, which while not quite identical for every machine, would be based on the same technology deployed in the same way. And because exports are the lifeblood of such an OEM, flexibility to meet different counties’ standards had to be designed in from the outset.

Even the largest bottle tops are not that big, so handling them at the speeds required can appear impossibly fiddly.

“Our philosophy is to have a simply machine design that avoids extraneous parts,” says Roger. “This lead us to the idea that we’d like the torque sensor to be wireless.”

Looking at torque sensors available on the market, one, TorqSense from Sensor Technology in nearby Banbury, stood out as meeting all criteria: simplicity, robustness, high speed and wireless. The company was contacted and design meetings set up.

Mark Ingham of Sensor Technology takes up the story: “Basically we could use TorqSense ‘as is’ for this application; we just needed to work out mounting arrangements. Similarly, the associated software was ready to go after a bit of calibration and some front end graphics.”

TorqSense is wireless in that it does not need to physically contact the bottle caps or shaft of the torque head it is monitoring. Instead sensing is achieved through a radio frequency link. Two tiny piezoelectric combs are attached to the shaft of the torque head, perpendicular to one another and at 45deg to the axis of the shaft. These form half of a Wheatstone bridge circuit, which is in radio contact with the other half in the main body of the TorqSense.

“When the shaft rotates a phenomenon known as Surface Affect Waves causes one comb to expand and the other to contract, changing their electrical resistance in proportion to the speed of rotation” explains Mark. “This unbalances the bridge and generates a signal indicating the torque value.”

With the Capcoder project, software was required to do two things: run the torque up to 10kgcm within tolerances of 10 percent, and record the actual value achieved. This secures the cap to the bottle at a level of tightness that will ensure security and sterility, yet is at a level that can be opened relatively easily by an adult. The logged values are saved to a hard drive to provide a permanent record for traceability purposes.

Roger explains: “Diagnostic fluids are distributed widely, typically to every hospital in the country, where they may be stored for months before use. Tracing each bottle’s origin would be practically impossible without full records being automatically produced and saved to a central location.

“We found a solution to this complex but critical problem using an out of the box technology. And what amazes me is the diversity of other fields in which TorqSense is used – its really any machine with a rotating shaft.”