Testing conditions for tank testers.

19/06/2016

In addition to the financial implications of the loss of product, leakage from storage tanks can cause serious environmental damage and represent a grave threat to health and safety. In some circumstances, particularly when the stored materials are combustible or explosive, leakage can result in a major incident involving the loss of life and substantial damage to assets and to an organisation’s brand. Regular inspection of tanks is therefore essential in order to identify any potential for future leaks, arising from corrosion, damage or insufficient material thickness or strength.

The variability in tank type, age and condition means that a wide variety of technologies are required in order to conduct effective inspections. The data derived from this work is used to inform an effective tank maintenance, repair and replacement programme. A rigorous inspection programme therefore reduces risk and avoids downtime; protecting sites from environmental and safety impacts, and the costs associated with decontamination and clean up.

TankInspection_Ashtead

Steve Drake, Ashtead’s NDT Market Manager, believes that the most efficient approach to the maintenance of tank structural and operational integrity is based on a flexible non-intrusive inspection programme. He says: “Routine calendar-based inspections that rely on historical data, such as fabrication material and age, risk ignoring current conditions and environmental factors. In contrast, we have customers using a range of inspection instrumentation that enables the assessment of current tank condition, often without interrupting tank service, so that an appropriate inspection frequency can be determined.

“By employing a range of technologies, inspection engineers are able to ensure that all potential risks are assessed, and that inspection frequency is optimised to minimise costs.”

Inspection also helps demonstrate compliance with relevant standards and codes, and provides reliable data on tank capacity; ensuring safe storage of materials such as chemicals, petroleum products and liquefied gases in both underground and above ground tanks.

A wide variety of technologies are employed for the inspection of tanks, and these instruments are amongst the most popular in Ashtead Technology’s fleet of rental equipment. The company’s customers are able to select instruments for Non Destructive Testing (NDT), providing data for thickness, corrosion, cracks, flaws and weld integrity. Remote Visual Inspection (RVI) instruments are also available to inspect the difficult to access locations that exist inside most tanks.

Tank inspection case study – anaerobic sludge digesters
An Ashtead Technology customer was contracted by a British utility to inspect its anaerobic digestion (AD) tanks. In applications involving potentially explosive gases, an intrinsically safe certified push-rod inspection camera is recommended. Following the development of a customised access point, inspection engineers were able to produce comprehensive images and videos showing the condition of the digester’s roof and walls.

The tanks were fabricated in GFS (Glass-Fused-to-Steel), a material which combines the strength of flexibility of steel with the corrosion resistance of glass. Consequently, GFS is commonly employed in applications with aggressive environments such as those inside anaerobic digesters – high temperature, high humidity, methane and hydrogen sulphide. An intrinsically safe Pearpoint P374 camera system was used to inspect the AD tanks, in conjunction with a digital video recorder.

Commenting on the success of the project, Ashtead’s customer said: “We built a customised ‘launch tube’ on one of the purge points on the roof and attached nylon to the camera tip so that we could video every surface once the probe was lowered into the ‘live’ digester.

“We were delighted with the results of the survey because we were able to demonstrate the condition of the tank very effectively, without having to decommission the digester.

“We were very impressed with Ashtead Technology because they ensured that we utilised exactly the right kit, and it was delivered and collected very quickly, which helped keep our costs to a minimum.”

Vessel inspection case study – chemical manufacturer
A chemical manufacturer in the North West of England had a requirement to inspect a large stainless steel vessel. The contents of the vessel were typically saline and varied between 50 and 100 Deg C, so the site managers were concerned that stress corrosion cracking might be a possibility.

Inspection engineers believed that Eddy Current Testing with the Eddyfi Ectane Surface Inspection System Ectane would be ideal for this application, so an Ectane was taken to the customer’s site to provide a demonstration. To test the Ectane’s ability to detect stress corrosion cracking in 10mm stainless steel, the client provided a test sample for inspection, and a flaw was correctly identified. As a result, Ashtead’s customer was awarded a contract to inspect the vessel and an Ectane was hired specifically for this purpose.

The Ectane is a multi-technology test instrument, and in addition to Eddy Current Testing, it is also able to perform Eddy current array (ECA), Remote-field testing (RFT), Near-field testing (NFT), Magnetic flux leakage (MFL) and Internal rotating inspection system (IRIS) ultrasonic tube testing.

The external inspection of the vessel took around 2 hours and covered a surface area of around 16m2 and the vessel was found to be free from any detectable stress corrosion cracking. Commenting on the effectiveness of the inspection technology, Ashtead’s customer said: “We have been very pleased with the Ectane; eddy current testing worked very well and at just 7Kg and battery powered, the instrument has been well designed for field applications.

“Our engineers wore rubber boots, gloves and goggles, but the Ectane was still simple to operate, partly because it can be run independently of a computer. Once the work was complete, the instrument was connected to an office PC running ‘Magnifi’ software, which is supplied with the instrument, and this provided a quick and easy method for analysing the data and helping to produce reports.”

Specialist tank inspection technology
In addition to a wide range of NDT and RVI equipment, Ashtead’s fleet of rental instrumentation now includes some of the latest technology for fast, effective tank inspection. For example, Silverwing, a leading manufacturer of NDT solutions for storage tanks, vessels and pipe inspection, has appointed Ashtead Technology as its Preferred Rental Partner in the UK. The Silverwing products offer motorised magnetic inspection; the Scorpion for example, can inspect vertical, curved and even overhead surfaces.

Designed for cost-effective A and B-scan inspection on ferro-magnetic structures, the Scorpion is a dry-coupled UT crawler that connects with the UT Lite data acquisition instrument via a 30 meter umbilical cord. This removes the cost and safety issues associated with scaffolding or rope access. The UT Lite is a portable corrosion profiling, mapping and weld inspection system that can also be used in conjunction with the R-Scan; a manual, dry-coupled ultrasonic scanner for a wide variety of assets ranging from 50 mm diameter pipes to flat surfaces.

Other Silverwing additions to the Ashtead Technology fleet include the RMS2 (Rapid Motion Scanner) a high speed (17m2/8 hour shift), high accuracy, remote access ultrasonic corrosion mapping system and the RMS2 ARC accessory for longitudinal scanning on pipe diameters from 24” to 48”.

Summarising the importance of technology selection, Steve Drake says: “Every tank is different; not just in age and material of construction, but also in build quality and operational conditions. The environment can also have a significant impact on tank quality and integrity, as can operational conditions.

“It is vitally important that all potential risks are assessed, which is why we offer such a wide range of the latest technologies; offering customers the opportunity to make sure that they use the most appropriate inspection tools for every tank or vessel.”

@ashteadtech #PAuto #NDT

Wireless production test.

07/08/2015

The Wireless Test System (WTS), is a solution from National Instruments (NI), that dramatically lowers the cost of high-volume wireless manufacturing test. Although faced with the rising complexity of wireless test, companies can confidently reduce test costs and multiply throughput on the production floor with a system optimised for measurement speed and parallel test.

wts_05_bdr“Megatrends, such as the Internet of Things (IoT), will push more devices to include RF and sensor functionality, which has traditionally been expensive to test. But test cost shouldn’t limit innovation or the economic viability of a product,” said Olga Shapiro, Program Manager for Measurement and Instrumentation at Frost & Sullivan. “To remain profitable in the future, companies will need to rethink their approach for wireless test and embrace new paradigms. Because the WTS is built on the industry-proven PXI platform and backed with the market expertise of NI, we expect it to have significant impact on the profitability of the IoT.”

The WTS combines the latest advances in PXI hardware to offer a single platform for multi-standard, multi- DUT and multi-port testing. When used with flexible test sequencing software, such as the TestStand Wireless Test Module, manufacturers can significantly improve instrument utilization when testing multiple devices in parallel. The WTS integrates easily into a manufacturing line with ready-to-run test sequences for devices that use chipsets from suppliers like Qualcomm and Broadcom as well as integrated DUT and remote automation control. With these features, customers are seeing considerable efficiency gains from their RF test equipment and further reducing their cost of test.

“We tested multiple wireless technologies ranging from Bluetooth to WiFi to GPS and cellular all with the same equipment using the NI Wireless Test System,” said Markus Krauss, HARMAN/Becker Automotive Systems GmbH. “The WTS and NOFFZ’s RF test engineering expertise helped us significantly reduce test time and the time it took to get our test systems up and running.”

The WTS is the latest system from NI built on PXI hardware and LabVIEW and TestStand software (see the Semiconductor Test System launched in 2014). With support for wireless standards from LTE Advanced to 802.11ac to Bluetooth Low Energy, the WTS is designed for manufacturing test of WLAN access points, cellular handsets, infotainment systems and other multi-standard devices that include cellular, wireless connectivity and navigation standards. Software-designedPXIvector signal transceiver technology inside the WTS delivers superior RF performance in the manufacturing test environment and a platform that can scale with the evolving requirements of RF test.


EMC tests find higher uptake as wireless technology gains currency. #PAuto

26/05/2014

The wider integration of wireless technology into products that were previously wired has caused a steady shift in electromagnetic compatibility (EMC) test services from classic or non-wireless testing to wireless testing. This trend, along with the proliferation of smart devices, has resulted in a higher number of new frequency bands. The greater density of frequency bands, in turn, has created a need for noise and emission reduction, making a strong case for enhanced EMC tests and services. 

Cartoon Science Borealis

Cartoon Science Borealis

New analysis from Frost & Sullivan, The European Electromagnetic Compatibility Test and Services Market, finds that the market earned revenues of $405 million in 2013 and estimates this to reach €409.6 million ($557.8m) in 2020. 

“With the integration and implementation of new technologies as well as the increasing complexity of electronic equipment, customers will require enhanced types of testing services,” said Frost & Sullivan Measurement & Instrumentation Research Analyst Rohan Joy Thomas. “Consequently, there will be the demand for EMC test equipment such as electromagnetic interference (EMI) test receivers, which are capable of more and quicker measurements, and spectrum analysers that are faster as well as more efficient and versatile.” 

The market will be sustained by the advances in the automotive industry, where there is intense activity around electric and hybrid vehicles. Electric and hybrid cars consist of a high voltage power source, an electric motor, a frequency convertor as well as high power cables. The high voltage power source could lead to more emissions of radiation, which can pollute the environment, or interfere with other electric equipment. 

To ensure that the vehicle is electromagnetically compliant with its surroundings, original equipment manufacturers (OEMs) require EMC testing services and consultations from a market participant with significant expertise in this domain. Overall, the higher sophistication of electric and hybrid vehicles generates a need for upgraded EMC test equipment and systems. 

However, although opportunities are plenty, the maturity of the market hinders the growth of smaller participants. As suppliers of EMC testing equipment and test services build their reputation on experience as much as technical expertise, it will be difficult for a market entrant to break into the market. The high investment costs are also significant entry barriers to a fragmented and price-sensitive market. 

“In such a scenario, participants tend to pull out all stops to retain their customer base – primarily by providing exceptional customer services and international standards of testing,” noted Thomas. “As EMC testing equipment and test services are highly specialized, participants have to constantly offer technological innovations and act as one-stop shops for customers.” 

The European Electromagnetic Compatibility Test and Services Market is part of the Test & Measurement Growth Partnership Service program. Frost & Sullivan’s related research services include: Global Sensor Outlook 2013, European Fiber Optic Test Equipment Markets, Western Europe General Purpose Test and Measurement Equipment Market, Analysis of World Markets and Trends for System-in-Package (SiP) Technology and World Densitometers and Profilometers Markets. All research services included in subscriptions provide detailed market opportunities and industry trends evaluated following extensive interviews with market participants. 


Is hiring instruments a good safety bet?

12/05/2014

Why instrument hire makes occupational safety sense!

Decisions concerning the acquisition of occupational safety monitoring instrumentation are often made by operational staff that may not have visibility of the full financial implications of their choices. This article, by James Carlyle of Ashtead Technology, examines the factors affecting these decisions and explain why a strategic decision to hire instrumentation can deliver substantial and wide-ranging advantages.

Background
The Management of Health and Safety at Work Regulations 1999 (originally introduced in Britain 1993 in response to an EU Directive) require employers and self-employed people ‘to carry out a suitable and sufficient assessment of the risks for all work activities for the purpose of deciding what measures are necessary for safety.’  However, the risks arising from toxic gases, dust, explosive mixtures and oxygen depletion can be complex and constantly changing. So, in addition to an initial risk assessment, ongoing monitoring is often necessary to ensure the protection of staff and others.

Employers may choose to conduct their own testing and monitoring, or they may prefer to employ the services of professional consultants to conduct the risk assessments. Either way, the employer of the consultant has to decide whether to purchase the instrumentation or to rent it.

The risks
Before examining the ways in which testing and monitoring should be undertaken, it is first necessary to consider the risks that need to be assessed.

Fire and/or an explosion can result from an excess of oxygen in the atmosphere, for example, from an oxygen cylinder leak, or an explosion may occur from the ignition of airborne flammable contaminants that may have arisen from a leak or spillage from nearby processes.

Toxic gas detection

Toxic gas detection

Toxic gases, fumes or vapours may also arise from leaks and spills, or from disturbed deposits or cleaning processes. Gases and fumes can accumulate in confined spaces such as sewers, manholes and contaminated ground. They can also build up in confined workspaces for welding, flame cutting, lead lining, brush and spray painting, or moulding using glass reinforced plastics, use of adhesives or solvents. Carbon monoxide, particulates and hydrocarbons may also become a problem in situations where the products of combustion are not exhausted adequately. Plant failure can also create gaseous hazards. For example, ammonia levels may increase if refrigeration plant fails or carbon dioxide may accumulate in some pub cellars following leaks from compressed gas cylinders.

Oxygen depletion in workplace air can cause headaches, breathlessness, confusion, fainting and even death. There are many situations in which this can occur; for example:

  • Workers breathing in confined spaces where replacement air is inadequate
  • Oxygen consumption by biological processes in sewers, storage tanks, storm water drains, wells etc.
  • Fermentation in agricultural silos or in brewing processes
  • Certain goods in cargo containers
  • Vessels that have been completely closed for a long time (particularly those constructed of steel) since the process of rust formation on the inside surface consumes oxygen
  • Increased levels of carbon dioxide from wet limestone chippings associated with drainage operations
  • Combustion operations and work such as welding and grinding
  • Displacement of air during pipe freezing, for example, with liquid nitrogen
  • Purging of a confined space with an inert gas to remove flammable or toxic gas, fume, vapour or aerosols
TSI Dustrak

TSI Dustrak

The COSHH definition of a substance hazardous to health includes dust of any kind when present at a concentration in air equal to or greater than 10 mg/m3 8-hour TWA of inhalable dust or 4 mg/m3 8-hour TWA of respirable dust. This means that any dust will be subject to COSHH if people are exposed above these levels. Some dusts have been assigned specific Workplace Exposure Limits (WELs) and exposure to these must comply with the appropriate limit.

Most industrial dusts contain particles with a wide range of size, mass and chemical composition. As a result, their effects on human health vary greatly. However, the Health & Safety Executive (HSE) distinguishes two size fractions for limit-setting purposes termed ‘inhalable’ and ‘respirable’.

Inhalable dust approximates to the fraction of airborne material that enters the nose and mouth during breathing and is therefore available for deposition in the respiratory tract. Respirable dust approximates to the fraction that penetrates to the gaseous exchange region of the lungs. Where dusts contain components that have their own assigned WEL, all the relevant limits should be complied with.

The financial justification for instrument hire
For most of us, when we need something, assuming funds are available, we buy it. At Ashtead Technology, we challenge that assumption; unless the required instrument is either very low cost or likely to be deployed on a frequent basis, it rarely makes sense to purchase the equipment. There are many reasons for this, but the most important is of course financial, however, operational staff are not always aware of the full cost of purchase, because the detail is hidden in the company’s accounts.

Capital purchases are generally written off in the company accounts over a 3, 4 or 5 year period. This means that the cost of ownership is at least 20% of the capital cost per year and possibly over 33%. However, there are of course other costs of ownership – most instruments require regular maintenance and calibration which itself involves further costs both in terms of materials and labour. A gas analyser, for example, would require calibration gases and associated valves and safety equipment; trained staff would be required to ensure that the instrument is calibrated correctly, and consumables such as filters and replacement gases would be required. The same issues arise with other types of instrumentation; all of which require maintenance by suitably trained and qualified staff. Consequently, the annual cost of instrument ownership can easily exceed 50% of the purchase cost.

Another significant financial cost is the ‘opportunity cost’ of the money that is tied up in a purchase; capital expenditure on equipment represents money that could have been used for other purposes – for investing in raw materials, staff, training, marketing, new premises etc. Alternatively that money could have been invested and delivered a return.

In addition to the financial justification, there are many more reasons to hire…

Renting provides appropriate technology
Once an instrument is purchased, the company is committed to that technology for the next few years and this can be a major disadvantage. For example, if a company purchases a PID gas detector for the measurement of solvents, it may find later that there is also a requirement to monitor methane, and the PID would not be suitable for this, so a second analyser would be necessary; an FID for example. Similarly, the company may discover at a later date that solvent speciation is necessary, which again, the PID would fail to achieve.

The same principle applies to other applications. For example, if a basic infrared camera is purchased and it later transpires that higher resolution images are required, a second more expensive camera would be necessary.

From a corporate perspective, instrument purchase can have negative implications because instruments are often shared amongst different departments and between different sites. However, it is unlikely that one technology or one particular instrument is able to meet everybody’s needs, so it is likely that each person will seek to acquire their own instrument; firstly to ensure that they get the kit that they need, but also so that their access to instrumentation is not limited because it is in use elsewhere. If each person is allowed to purchase their own kit; whilst this might be an extremely costly option, it does at least encourage ‘ownership’ so that the equipment is properly maintained. In contrast, shared ownership often results in poor maintenance because none of the staff take responsibility for ensuring that the equipment is serviced and maintained correctly.

Renting instrumentation ensures that all staff have continual access to a range of different technologies, so they do not have to ‘make do’ with whatever happens to be available at the time they need it. If a company has purchased an instrument, its staff are more likely to use it ‘because it is there’ rather than because it is the most appropriate technology.

Renting provides access to new technology
One of the problems with buying an instrument is that your technology is then stuck in a moment of time; inevitably new instruments are developed that are better than their predecessors, but once an instrument has been purchased it is not possible to take advantage of new technology. In contrast, with the benefits of scale, Ashtead is able to continually invest in new technology so that the rental fleet provides access to the latest technology and customers are therefore able to choose the instruments that best meet their needs.

Renting eliminates storage and maintenance costs
One of the common features of all instruments is that they require regular maintenance and in many cases calibration. This is often a skilled activity that requires training and appropriate equipment. Ashtead Technology’s engineers are therefore equipped with all of the necessary equipment to service and maintain every instrument in the rental fleet. They are also trained by manufacturers, so that all instruments can be delivered tested and ready for immediate use. Storage can also represent a cost for the larger pieces of equipment, especially if it is not possible to store the instruments in the same location as the main users.

Technical support from rental companies
Instrumentation is constantly evolving; newer instruments are usually more accurate, more sensitive, faster, lighter, and easier to use. However, the array of instruments available can be bewildering so it is often helpful to discuss options with an Ashtead Technology engineer before making a choice, and then after the instrument is delivered, many customers value telephone support during the setup and operation of the instrument.

Summary
The basic premise behind Ashtead Technology’s business is an intense focus on providing customers with exactly the right equipment at the precise moment that they need it. We therefore seek to become our clients’ instrumentation partner; saving them time and money, and ensuring that they always have access to the best available technologies. This is achieved by:

  • Continually searching the market, looking for the best technologies from the world’s leading suppliers
  • Utilising expert knowledge and buying power to ensure that our fleet of instruments includes a broad selection of the best available technologies
  • Manufacturer training for our engineers
  • Investing in the equipment, spares and consumables for servicing, calibrating and maintaining the entire instrumentation fleet

We invest in these measures so that our clients don’t have to.


Smarter phones drive mobile data monitoring!

02/04/2014
Expansive increase of smartphone use creates a need for mobile data monitoring solutions!

Over the next five to ten years, data traffic is expected to increase exponentially due to the growing adoption of smartphones globally. This amplified volume of data will place considerable strain on the networks of communication service providers (SPs)  and their information management systems, thereby stoking demand for mobile data monitoring systems.

smtphnsMobile data monitoring solutions are critical tools to improve overall mobile data performance and customer experience, as these can analyze mobile data and optimize the performance of their networks.

New analysis from Frost & Sullivan, Global Mobile Data Monitoring Market, finds that the market earned revenue of $312.4 million in 2013 and estimates this to more than triple, reaching $1.103 billion in 2020, at a compound annual growth rate of 19.8 percent.

Due to the rocketing adoption of smart devices, mobile apps and video are expected to be the most consumed types of data. This growth is unlikely to dip, as social networking traffic and machine-to-machine (M2M) communication continues to rise in popularity. Over the next five years, M2M traffic is expected to outstrip even that of social networking traffic, as connected devices and sensors are anticipated to exceed 50 billion units.

Currently, SPs are ill equipped to deal with this demand for data.
“Communications SPs must invest in mobile data monitoring solutions to ensure positive end-user experience and lower customer churn,” stated Frost & Sullivan Communications Test & Measurement Program Manager Olga Yashkova-Shapiro. “Already, many SPs have rolled out Long-Term Evolution (LTE) networks and are exploring other data traffic offload strategies to keep pace with demand.”

Adoption of over-the-top applications stimulates market growth
In addition to the adoption of smart phones, over-the-top (OTT) applications are contributing to the mounting demand for mobile data monitoring solutions. The swelling data traffic is forcing telecom companies to invest in more secure and complex testing capabilities to match strides with network expansions as well as upgrades in 3G and LTE.

Consumers are demanding more bandwidth-hungry applications, which require operators to deploy faster transmission links. When mobile users log on to 3G networks, they expect the applications to work seamlessly. Moreover, the information received from these different networks must be correlated.

Although the adoption of LTE has helped achieve the required data rates, there are significant concerns about the quality of voice and data. Companies are hoping to mitigate these issues with the adoption of voice over LTE (VoLTE), an IP-based multimedia system standardized by the third-generation partnership project (3GPP) to maximize international interoperability. VoLTE allows SPs to reduce the cost of delivery, enhance voice service offerings, and combat the service degradation in OTT services such as Skype and Viber.

“Traditional voice monitoring or service assurance solutions were not designed to analyze voice delivered over a data network,” notes Yashkova-Shapiro. “Therefore, the demand for next-generation mobile data monitoring solutions to support VoLTE is expected to increase and more operators are investing in new mobile devices required to support the VoLTE standards.”

Overall, SPs’ keenness to provide the highest levels of quality of service and quality of experience is expected to sustain the demand for comprehensive management solutions and proactive monitoring.


Testing in 2014 – looking forward!

28/02/2014

National Instruments has released its Automated Test Outlook 2014, highlighting the company’s research into the latest test and measurement technologies and methodologies. Engineers and managers can use the report, which examines trends affecting a wide range of industries, to take advantage of the latest strategies and best practices for optimising any test organisation.

ato_2014_4_colThis look into the future explores the following:

Business Strategy: Organisational Proficiency
The talent pool for test engineers is shrinking and test managers must improve organisational proficiency through smarter hiring, better onboarding and greater investment in training to ensure a properly skilled and staffed test organisation.

Architecture: Managed Test Systems
New technologies deliver greater feature sets on test equipment, helping test managers monitor the health of their test systems, lowering test costs and maximising uptime.

Computing: Cloud Computing for Test
Traditional test frameworks limit profitability by not providing the ideal balance of performance and cost or the ability to scale based on actual product demand. Similar to the IT industry, cloud computing applied to automated test can alleviate these growing test concerns.

Software: Scalable Test Software Architectures
Pressure to deliver test systems faster with fewer resources shifts software strategies away from rigid, inflexible solutions in favour of software-based platforms to maximise longevity and scalability across a product’s lifecycle and across new product designs.

I/O: Redefining the Notion of Sensors
The number of sensors in products has significantly increased, challenging test managers to keep up with new technologies and adapt to this growing need. Test managers need agile test solutions they can change as quickly as the sensor-integrated products they test.

Automated Test Outlook 2014 is based on academic and industry research, user forums and surveys, business intelligence and customer advisory board reviews.


Discrete or Continuous Flow Analysis – which is better?

28/01/2014

A wide variety of factors affect the choice of analytical instrument. These include target workload (samples/hour), variety of chemistries, methods required, bench space, staff availability etc. In the following article Lalicia Potter, Technical Sales & Support Director at SEAL Analytical, examines one of the common decisions facing laboratory managers.

As the manufacturer of an instrumentation range that includes both discrete analyzers and continuous segmented flow analyzers, SEAL Analytical’s technical support chemists are often asked which is the better technique. Both offer fast, automated, colorimetric analysis of multiple samples, however, the answer depends on the current and future analytical requirements of the laboratory.

Descrete Analyser

Descrete Analyser

SEAL’s discrete analysers employ sample trays and discrete reaction wells in which the colorimetric reaction takes place. In contrast, segmented flow analysers (SFA) employ a continuous flow of samples and reagent, segregated by air bubbles within tubing and mixing coils.

In general terms, discrete analysers are ideal when automation is a priority and/or when many and varied tests are needed on different samples. SFA is ideal when a larger number of samples are to be analysed for a smaller number of chemistries. However, both techniques are flexible, so it is important that expert advice is sought in the choice of analyzer and that the instrument is configured to meet the precise needs of the laboratory.

Discrete Analysers
In order to minimise operator involvement, SEAL’s discrete analyzers are highly automated and simple to set up and run, even overnight. A robotic sampling arm works in conjunction with a stepper motor-driven syringe that is responsible for aspirating, dispensing and mixing accurate and precise quantities of sample and reagent. The SEAL AQ1 and AQ2 discrete analyzers can run seven different chemistries from each sample in the same run – and another seven in another run. These instruments have three separate wash stations including a unique probe washer, so cross-contamination is not a problem. This unique washing feature means that even ammonia (using Phenate), nitrate by cadmium reduction– (using ammonium chloride buffer) and low level phenol can be run together with no issues.

SEAL has also built an auto-dilution feature into the discrete analysers for preparing standards automatically and handling over-range samples. These diluted sample results are automatically bracketed by QC sets.

The reproducibility and detection limits of these discrete analysers have been optimised by ensuring that each sample is read in the same optical glass cuvette with a 10mm path length. The sample is always read in the same position in front of the detector, which eliminates any potential issues with scratching or reaction well variability that can be found with direct-read systems. Since the liquid is moved and not the tray; fewer moving
parts maximises reliability.

Most discrete analysers employ miniaturised components to reduce reagent consumption and waste costs. For example, both the AQ1 and AQ2 analysers use just 20 to 400µl of reagent per sample.

Segmented Flow Autoanalysers
Based on the original tried and tested technology of the Technicon™ /Bran Luebbe™ AutoAnalyzer, today’s SFAs deliver fast, accurate analysis for enormous numbers of samples; the QuAAtro for example can run up to 600 tests per hour. SFA’s are also highly automated and once the analyzer is configured and the reagents and samples are loaded, reliable unattended operation is a major benefit.

Flow Analyser

Flow Analyser

A basic SFA system consists of an autosampler, a peristaltic pump, a chemistry manifold, a detector and AACE data acquisition software. Sample and reagents are pumped continuously through the chemistry manifold and
air bubbles are introduced at precisely defined intervals, forming unique reaction segments which are mixed using glass coils. With SFA, even slow reactions run to completion and the ratio of sample to reagents in the detector reaches a constant maximum value; the steady-state condition.

SFAs have been developed for running a few parameters on a larger number of samples, and the SEAL SFAs are the system of choice for marine and seawater organisations and anyone running very low nutrient waters. The SEAL AutoAnalyzer 3 and QuAAtro deliver high levels of performance and reproducibility, and are also the systems of choice for tobacco, soil and fertiliser testing around the world. These analysers provide maximum sensitivity by ensuring that the reaction always goes to completion, and with a digital true dual-beam detection system with real time referencing, the highest reproducibility and very lowest detection limits are achieved.

In summary, when choosing the most appropriate analytical technique, it is important to consider both the current and likely future needs of the laboratory. However, one of the reasons behind the large numbers of SEAL instruments in laboratories around the globe, is that each analyzer has been configured to meet the individual needs of its laboratory. So, it is good practice to contact SEAL’s technical support team at an early stage because if the question is: “Which technique is better,” the answer is: “It depends…”