Pre conference conference on Mercury as a Global Pollutant

02/08/2013
This is a brief summary of the Press Conference that preceeded the Mercury 2013 conference in Edinburgh (28 July – 2 August 2013 Scotland).
mercurypconf

Panel members: Loic Viatte, Swedish Ministry for the Environment, Dr Lesley Sloss, Chair of Mercury 2013 and Principal Environmental Consultant at IEA Clean Coal Centre and Lead – Coal Mercury Partnership area at the UNEP, John Topper, Managing Director, IEA Clean Coal Centre and Managing Director of the GHG Group, Dr David Piper, Deputy Head of the Chemicals Branch of UNEP’s Division of Technology Industry and Economics, Michael Bender, co-coordinator of the Zero Mercury Working Group, Eric Uram, Executive Director of SafeMinds, Prof. K. Clive Thompson, Chief Scientist at ALcontrol Laboratories UK.

The panel discussed the progress of legislation to reduce emissions from coal-fired power stations and Dr Lesley Sloss explained that, whilst mercury-specific legislation may take 5 to 10 years to be implemented in Europe, control technologies which can reduce mercury emissions by around 70% are already being utilised in many countries as part of initiatives to lower emissions for pollutants such as particulates, sulphur dioxide and nitrogen oxides. However, it was suggested that some developing countries and emerging economies may choose to implement these technologies as part of their commitment to the Minamata Convention.

rialtasalbaIn advance of the Press Conference, Paul Wheelhouse, Scottish Government Minister for Environment and Climate Change, issued the following statement:“An international conference of this stature puts Scotland on the world stage and demonstrates the important part we are playing in addressing global issues.
“Sound science, strong evidence and engaged citizens means properly informed choices and effective action on the ground and this is essential if the harmful effects of mercury pollution are to be reduced.
“This event is a key part of the journey to a new legally binding international agreement – and Scotland should take great pride in being at the heart of that process. I’d like to warmly welcome all of the 850 delegates from over 60 countries to Edinburgh and wish them every success as they progress this crucial agenda.”

Discussing the different priorities for the week’s conference, Michael Bender said “Mercury knows no boundaries which is why it has been necessary to develop an international convention.” One of the main sectors facing a mercury emissions reduction requirement is illegal artisanal gold mining, but this is a challenging social issue because gold mining is the sole source of income for many of these miners. Enforcing legislation could have very serious social consequences. In contrast, the coal industry, responsible for around 25% of the global emissions from human activities, around half of that from artisanal gold mining, is easier to regulate so this is often regarded as a more tempting target for guaranteed results.

Michael Bender also referred to the benefits of trade barriers which are beginning to halt the flow of mercury between countries, so there is a need for this trend to continue and for more chain of custody regulations.

The panel explained the need to ‘’think globally, act locally” – to acknowledge that mercury distributes itself around the globe with no respect for national borders but to appreciate that all countries may play their part to clean up their own back yard.

One of the priorities will be to address the mercury issues that are the quickest and easiest to address; the low-hanging fruit. The panel felt that this would be the products that contain mercury; especially in the healthcare sector (thermometers and similar instrumentation) because of its ‘do no harm’ ethos and the increasing availability of alternative methods and instruments.

One of the most important issues in delivering the aims of the Convention is ‘political will’ to drive change. For example, the election of President Obama was seen as a significant moment in the development of the Convention because he had already addressed mercury issues earlier in his political career. David Piper said that the support of the United States was very significant in the development of the Minamata Convention.

Michikazu Iseri from the Kumamoto Daily News in Japan asked the panel if NGOs are likely to be disappointed with the Convention, but Michael Bender from the Zero Mercury Working Group (an international coalition of over 100 NGOs) said that, whilst many of them might have preferred greater rigour in the terms of the convention, the overall reaction was very positive because the Convention combines both a financial mechanism and a compliance mechanism. David Piper agreed, describing the Convention as a ‘giant step forward’ but Lesley Sloss said the challenge now is to flesh the convention out with more ‘what and how’ detail.

The final question referred to the adoption of low energy compact fluorescent lightbulbs (CFLs) that contain a small amount of mercury; whilst helping to lower energy usage, they contribute to mercury emissions. Responding, David Piper said that he did not expect this to become a significant issue since these technologies are likely to be replaced with even more environmentally friendly options in the near future.


State of control and safety in manufacturing and power generating industries!

29/07/2013

This paper was written by a team at Premier Farnell. Premier Farnell is a distributor of electronics technology.

The power generation industry has gone through many changes in the last 50 years or so and the controls and safety features that were based primarily on the pneumatic controls are now taken over by electronic controls (with its own set of integrated systems resistors, and capacitors) and/or the Digital Control Systems, Furnace safeguard Supervisory Systems (FSSS) and computer controlled systems. The automation systems have improved over the years and now a standard has emerged for the power generating industries. The general improvements in the systems can be enumerated as below. The systems in a boiler control are generally divided in five sections; wiz, drum level controls, steam temperature control, boiler pressure controls, and furnace safeguard Supervisory Systems (FSSS) as also auxiliary interlocks; apart from the boiler water chemistry control. The boiler water chemistry is a separate control not normally associated with other controls and will not be discussed here.

System for drum level controls
Earlier the controls were based on water level in the drum. Sometimes when the steam demand went down the decrease in water level (because of increase of pressure) would tend to supply more water to the drum. This anomaly was rectified by the introduction of a three level control for the boiler drum. In the new system, the difference in the steam flow and the water flow was the main element for control of drum level with correction from drum level adding to the better control. The drum level system can be independent control with its own electronic controls consisting of resisters transistors and capacitors or integrated circuits.

Figure 1: Three element control

Figure 1: Three element control

The system was further refined with pressure and temperature correction from steam parameters. This resulted in better management of drum level. The three element control with the compensation has not undergone any major change over the last 50 years and is now the industry standard.

Figure 2: Three element controls modified

Figure 2: Three element controls modified

Control for boiler pressure
The pressure control has changed from just pressure control to the addition of other parameters like air flow, fuel flow, and the fuel calorific value for pressure control. The online efficiency calculations are also now integrated along with fuel pressure controls. The primary air, secondary air measurements also assists the control of boiler pressure in the system.

Figure 3: Boiler pressure control

Figure 3: Boiler pressure control

Furnace safeguard Supervisory Systems (FSSS)
The FSSS system makes sure that there is no uncontrolled fuel that can cause explosion in the boiler at any stage. The flame is sensed by photo sensors and as long as the flame is available, the supply of fuel is continued to the burners. The absence of flame shuts off all the fuel in the furnace system. Of course the flame sensing is done by two out of three sensors so that at any stage at least two sensors are working and any dependence on a single flame sensor is avoided. Failure of two sensors to see a flame is a signal to close all the fuel supply to the furnace. The fuel can be in solid, liquid or gaseous form. All the fuel in any form will be cut off irrespective of the condition of boiler pressure. The fuel supply cannot be re-started unless the complete purging of fuel is ensured. For ensuring of absence of any fuel in furnace, the furnace is purged with 30% of air flow for 5 minutes and then only the new supply of fuel can be introduced. The purging is done irrespective of the reason of trip. Here also better flame sensors and better

The functions of FSSS are,

  1. Starting of furnace purge after conditions of auxiliary interlocks are satisfied
  2. Permit starting of fuel introduction
  3. Making sure that burners start working only when an auxiliary flame exists
  4. Stopping of all fuel to boiler when flame is extinguished or no longer detected.

FSSS has three units, wiz indicating and operator’s console, relay and logic cabinet with its own electronic circuits of transistors, resistors and capacitors, relays, timers, AC and DC supplies and the fuel trip system.

Figure 4: Typical FSSS panel

Figure 4: Typical FSSS panel

Steam temperature controls
The steam temperature controls ensure that the metals used in construction of the boiler are below the safe limits under which they can operate. The control of steam temperature can be achieved by many means, but the most effective control is achieved by attemperation of steam in the area between the primary and the secondary superheaters. Any increase of temperature can affect the life of parts and may even cause failure of metals of the final superheater.

Figure 5: Steam temperature control

Figure 5: Steam temperature control

Boiler alarm panels that were previously hard wired have started to become much more sophisticated panels. For example, previously changing alarm settings was only possible with the help of an instrument engineer, now the operator of the panel is able to fine tune the alarm setting.

Figure 6: Boiler indicating and alarm panel

Figure 6: Boiler indicating and alarm panel

All these systems were operated as independent systems with no outside communication. These were known as single loop controllers with their own logic. The trip systems operated independently and had no effect on the other entities in a power plant like the turbine, generator or the electrical systems. Additional reliability was introduced with the help of two out of three systems of primary sensing elements. With all of them agreeing on the value of the sensing element, the average value was used for control. When one of them gave a value beyond a permissible error, it was ignored and the other two were used for calculations and an alarm about the third one going out of service was given to the operator. This increased the reliability of the system, something that was not possible with the pneumatic systems.

Other systems like the water management and fire fighting systems could not be integrated with the overall systems, even though operators could get information through hard wired systems. In emergencies, some of these systems were often ignored, resulting in less than ideal ways of handling the emergency.

The next major change was the introduction of a Digital Control System (DCS) and the use of software in the boiler control system. All the above controls were previously independent of one another, but the introduction of DCS and computer software in alarm and emergency handling systems brought the safe shut down of the boiler, turbine and generator. The system of programmable logic controls and the mechanical relays for protection of generators slowly gave rise to the electronic relays in electrical systems and its integration with the DCS.

The architecture of the DCS is local control supervised by additional layers that overlook the entire system. The individual control level of the drum, pressure control, FSSS of boiler, as well as the control of auxiliary interlocks turbine and generator protection, are individual systems which have their own logics and system of alarm generation for decentralized controls, but the information is sent to a higher level where the safety system takes over in emergencies.

In case of emergency situations in individual areas, the system can have its own set of controls over the change in parameters to handle the situation. The safety of the entire system takes precedence over the individual systems and the safe shutdown of the entire system gets activated.

While the individual controls are meant for the control of a single parameter, the alarm system signals the operator about the abnormal condition. The operator can take over the situation and bring the system back to normal. In case the operator is unable to do so and the situation threatens to get out of hand, the shutdown system comes into play. At this stage the operator cannot have any involvement and can only oversee the system shutting down safely.

Overall, the change from individual controls, to dedicated single loop controllers with redundant sensing elements to the DCS formed the line of change to the present method of state of control and safety in manufacturing and power generating industries.


Process Automation I/O module market driven by IS!

11/06/2013

A new ARC Global Market Research Study shows the market for process I/O module sales showed growth in 2012, yet with slower pace than in the previous two years.  In 2013, ARC expects the growth to stay at a low level, but will pick up the pace in 2014 and beyond.  The market for process I/O modules is mainly driven by two forces:  an increasing need for intrinsically safe I/O modules and the increasing demand from the Middle East and the BRIC countries.

While the process I/O modules market is large in Europe, Japan, and North America – and is expected to remain large – the growth regions will be Latin America, the Middle East, and parts of Asia, namely China, India, Vietnam, Korea, Thailand, Indonesia, and some other countries.  Looking at specific hardware types, intrinsically safe I/O modules, network adapters, and intelligent I/O will grow above the market average.

“The product portfolio of many suppliers of I/O modules shows a broad bandwidth of different types.  While big suppliers leverage their installed base, third-party suppliers of process I/O modules concentrate on specialized I/O modules and compatible I/O modules that fit to the control systems of the big suppliers,” according to Stefan Miksch, the principal author of ARC’s “Process Automation I/O Modules Global Market Research Study.

Intrinsic Safety
Intrinsically safe I/O modules are not a new type of I/O module nor have they changed in how they work.  The increasing amount of installed automation even in harsh and explosive environments makes intrinsically safe components essential.  In turn, the demand for intrinsically safe process I/O modules will grow above average and continue to do so beyond the forecast horizon of this study.

Oil & Gas and Electric Power – Drivers for Process Automation I/O Modules
The oil & gas and the electric power industry will be the fastest growing industries for process I/O modules.  Rising demand for energy and energy distribution will push these sectors above the average growth rates of other industries where process I/O modules are employed.

As these two industries are expected to perform well over the next five years, the demand for explosive protection automation solutions will rise, and in turn push demand for explosive protected or intrinsically safe process I/O modules.

Asia – Also Growth Region in the Future?
Asia needs to be separated into the emerging and mature countries.  While emerging Asia will contribute to the growth of the process I/O module market, mature Asia, more precisely Japan as the biggest market for process I/O modules in this region, will show growth rates explicitly below average.

Europe and North America still experience great uncertainty when it comes to the debt situation and financial markets and therefore growth rates in this regions are not expected to be at a significant high level.


Instruments to strike up in Music City USA!

02/04/2013

Attendee registration for ISA Automation Week 2013—the premier annual event for automation and control professionals worldwide is now open.

5049-AW-panel-for-2013

Leading automation and control experts, authors, innovators and thought leaders across the globe will come together at the event to demonstrate how to fully leverage the power and potential of automation solutions. Attendees will learn that decisions in one organizational area can have significant, sometimes adverse, effects in others, and that the key is addressing core operational needs—safety, people, business and technology—in a more proactive, farsighted and integrated manner. See our report on last years event in Orlando (FL USA) – Not a Mickey Mouse affair.

ISA Automation Week will be conducted 5-7 November 2013 in energetic and exciting Nashville (TN USA), also known as Music City USA!  Registration by 20 August 2013, will save $150 (say €120,00) off the full-price registration fee. Register Here!

ISA Automation Week Partners
ARC Advisory Group, the leading technology research and advisory firm for industry and infrastructure.
Beamex, a technology and service company that develops, manufactures and markets high-quality calibration equipment, software, systems and services for the calibration and maintenance of process instruments.
Cooper Bussmann Wireless, the manufacturer of North American- and European-styled fuses, and the producer of inductors and transformers for power quality in electronic applications and wireless solutions.
ExperTune, the designer of pre-packaged industrial software for the process industries worldwide.
Falcon Electric, a leading manufacturer of award-winning power protection and conversion solutions.
GE Energy Management, the designer of technology solutions for the transmission, distribution, management, conversion and optimization of electrical power across multiple energy-intensive industries.
MAVERICK Technologies (also an ISA Strategic Partner), a global leader in industrial automation, enterprise integration and sustaining services for clients across a wide range of manufacturing and process industries.
OSIsoft (also an ISA Corporate Partner), the leader in real-time data and events infrastructure through the PI System, a streaming data and event management software product for use in manufacturing, energy, utilities, life sciences, data centers, facilities and the process industries.

A new Attendee Networking Hub
Attendees and vendor companies will connect with conference attendees in ISA Automation Week’s new Attendee Networking Hub.
Dedicated space at the Nashville Convention Center will be provided for solutions providers to allow for direct and interactive contact with attendees. This gathering space – known as the Attendee Networking Hub – is ideally situated adjacent to the conference session rooms. The Attendee Networking Hub will be the focal point for workshops, presentations and solutions demonstrations as ISA Partners and suppliers make their technical experts, resources, solutions and product information available to conference attendees.
In addition, the Hub will be open for evening receptions, entertainment, and conference breaks.

Keep an eye on theCorporate Partners
ISA Automation Week’s Corporate Partners (see box on right!) are committed to helping attendees get the most out of their conference experience, and introducing to them new and innovative marketplace solutions.

These companies represent a group of select companies who serve the automation and control marketplace. Their partnership agreements with ISA provide them with the opportunities to offer their technical resources and expertise to conference attendees, and to demonstrate product applications and unique automation solutions.

ISA’s Corporate Partnerships Program offers companies customized packages, combining ISA products and services with marketing opportunities across all channels, and providing a streamlined approach to corporate sponsorship. ISA’s program features three main levels of sponsorship: ISA Strategic Partners, ISA Corporate Partners, and ISA Automation Week Partners. The program, in its fourth year, is limited to a select group of companies at each level to maintain the highest level of visibility for each partner.


Safer containers with FTIR

04/03/2013

antti HeikkilaThis paper, by Gasmet’s Antti Heikkilä, describes how sophisticated gas analysis is being used to check these cargo containers, but this is just one example of the advantages that are available from an analytical technology that can measure almost any gas.
Antti Heikkilä (right) is a senior manager at Gasmet Europe Oy, specialising in developing new applications for the Gasmet FTIR gas analyzers. He holds a MSc degree in Physical Chemistry and has 14 years’ expertise in FTIR spectrometry and quantitative gas analysis, working for the University of Helsinki and Gasmet Technologies group.

Introduction
Entry to freight containers represents a significant hazard to staff responsible for inspection, stuffing or destuffing because of the large number of airborne chemicals that can be present. Research in Germany and the Netherlands found hazardous levels of gases and vapours in around 20% of all containers and this level of contamination is now accepted as commonplace.

Container testing!

Container testing!

It is therefore necessary to examine containers before entry and this work is usually conducted with a wide variety of gas detection techniques in order to be able to assess, individually, all of the substances of greatest concern. However, a Dutch firm of health and safety consultants, Reaktie, has employed FTIR (Fourier Transform Infra Red) gas analysis to dramatically improve the speed and effectiveness with which containers are assessed, because this technology enables the simultaneous measurement of the 50 gases of most concern.

Chemical Hazards
There are two potential sources of hazardous chemicals inside cargo containers; fumigants and chemicals that arise from the goods or packing materials.

Fumigants are applied to goods to control pests and micro-organisms. Cargoes most likely to have been fumigated include foodstuffs, leather goods, handicrafts, textiles, timber or cane furniture, luxury vehicles and cargo in timber cases or on timber pallets from Asia.

According to the IMO’s international regulations, ‘Recommendations on the safe use of pesticides in ships’, fumigated containers and ship cargoes must be labelled giving specifications about dates of fumigation and the fumigation gas used. Furthermore, appropriate certificates are necessary and these records have to be forwarded to the Port Health Authorities without their explicitly asking for them. However, absence of marking cannot be taken to mean fumigants are not present. Containers marked as having been ventilated after fumigation may also contain fumigant that was absorbed by the cargo and released during transit. There is also concern that fumigants may be retained in the goods and subsequently present a hazard to logistics providers, retail staff and consumers.

Common fumigants include Chloropicrine, Methyl bromide, Ethylene dibromide, Sulfuryl fluoride and Phospine. However, with over 20 years of experience testing gases in containers, Peter Broersma from Reakti says “While the fumigants are highly toxic, the number of containers exceeding occupational exposure limits (OEL) due to other chemicals is much greater and the number of ‘failed’ containers is likely to rise as more containers are tested, detection methods improve and new gases are identified.”

Containers often travel for extended periods and experience a wide range of temperatures. It is therefore not surprising that unsafe levels of gases should accumulate in the confined space of a container. Peter identifies the typical sources of gases over their OELs as follows:

  • Solvents from glues used to produce clothing, accessories and shoes
  • 1,2, dichloroethane from plastic products, PVC, blister packaging etc.
  • Formaldehyde found in cheap furniture (Plywood,MDF etc.) but also in used pallets and lashing materials
  • Solvents and formaldehyde from poly-resin products
  • Carbon monoxide from charcoal and natural products
  • Carbon dioxide from natural products
  • Ethylene oxide from medical equipment sterilised with ethylene oxide
  • Solvents including Benzene, Toluene, Ethylbenzene and Xylene (BTEX) in Christmas and decoration products
  • Flammable gases from disposable lighters
  • Ammonia in household equipment with Bakelite parts
  • Volatile Organic Compounds (VOCs) from fire blocks
  • Pentanes and hexanes from consumer electronics
  • Phosphine/arsine from natural minerals such as ferrosilicon

Inspection procedures
Major ports have strict regulations in place to protect against potential hazards in cargo containers. In general terms, every incoming stream of products has to be checked for dangerous gases and if one of more gases are detected during the preliminary investigation, all of the containers from this specific producer must be checked. If no gases are detected, it may be possible to only conduct random tests a few times per year. If it is necessary for Customs staff to enter a container, all containers must first be tested and if necessary de-gassed.

Gas detection
Since there are a large number of gases that might be present inside a container, the traditional approach to monitoring has been either to employ a wide range of instruments or to use chemical stain tubes for the most common gases, or a combination of both.

Chemical stain tubes provide a colorimetric assessment of an individual gas, typically with an accuracy of +/- 15%. Different tubes are available for many gases and results can be obtained between 5 seconds and 15 minutes depending on the test. Once a result has been obtained, the tube itself is hazardous waste and must be disposed of. Historically stain tubes have been popular because the cost per test is low. However, the number of tubes that have to be employed in order to demonstrate that a container is safe can be prohibitively expensive and time-consuming to employ.

Instrumental gas analyzers such as electrochemical sensors, that measure either a single gas or a small number of gases impart a similar level of risk to stain tubes because of the possibility of missing or failing to measure a harmful gas. Deploying multiple instruments also presents practical problems because each will require maintenance and re-calibration in addition to a power source or re-charging. Nevertheless, Reaktie for example, would normally conduct a preliminary assessment with a PID gas detector for total VOCs; an LEL combustible gas sensor and handheld electrochemical sensors might be employed for toxic gases such as carbon monoxide, phosphine, ammonia and ethylene oxide. An FTIR analyser would then be employed to measure 50 target gases simultaneously in a test that would take approximately 3 minutes. This ability to measure compounds individually is important because, for example, whilst a PID gas detector measures total VOCs, it does not provide an individual value for, say, benzene, which is a known carcinogen.

One of the potential problems with electrochemical sensors is their inability to cope with high concentrations in a sample gas. This can result in poisoning of the cell, which would normally result in instrument failure. In contrast, similar high concentrations do not harm FTIR, and the instrument can recommence analysis after a few minutes of backflushing.

DX4040

Gasmet DX4040

Peter Broersma has been one of the first to utilise FTIR in the assessment of containers since it first became possible to acquire the technology in a portable battery powered unit. He says “The problems with hazardous gases in cargo containers is now widely publicised and the requirement for testing is growing as employers fulfil their responsibility to protect the health and welfare of staff. However, the traditional testing methods are laborious, time-consuming and risk failing to find a potentially harmful gas.
“FTIR has long been established as an accurate technology for the simultaneous measurement of gaseous emissions from industrial processes, so when the Finnish company Gasmet developed a portable version we were very eager to investigate its feasibility in container testing.
“Following our initial tests, we worked with Gasmet to develop a configuration for the portable FTIR (a Gasmet DX4030) that would measure the 50 compounds of greatest concern. As a result, we are now able to test for all of these gases in around 3 minutes, which dramatically lowers the time taken for container inspection and greatly increases the number of containers that can be examined every day.
“A further major advantage of this technology is the minimal amount of calibration and maintenance that is necessary. A new instrument can be delivered pre-configured and factory calibrated and from then on the only calibration required is a quick zero check with nitrogen once or twice per day. As a result, it is not necessary to transport a large number of expensive, bulky calibration bottles.
“We now use a portable FTIR for all of our container examination work and we have also supplied a number of these units to freight companies that wish to conduct their own testing. This technology is now in use at Rotterdam, Amsterdam, Vlissingen, Antwerp and Hamburg, and a company providing ship fumigation and degassing is using portable FTIR all over the world.”

Fourier Transform Infra Red (FTIR)
An FTIR spectrometer obtains infrared spectra by first collecting an ‘interferogram’ of a sample signal with an interferometer, which measures all infrared frequencies simultaneously to produce a spectrum.

Over a number of years, Gasmet has established a library of reference spectra that now extends to simultaneous quantification of 50 gases or identification of unknowns from a collection of 5000+ gases. This means that it is possible to
reanalyze produced spectra with the instrument’s PC based software (Calcmet) and thereby to identify unknown gases – a major advantage of FTIR.

Whilst FTIR is able to analyse an enormous number of gases, the technique is not suitable for inert gases, homonuclear diatomic gases (e.g., N2, Cl2, H2, F2, etc) or H2S (detection limit too high).

High levels of accuracy and low levels of maintenance are achieved as a result of continuous calibration with a He-Ne laser, which provides a stable wavenumber scale. In addition, high spectral signal to noise ratio and high wavenumber precision are characteristic of the FTIR method. This yields high analytical sensitivity, accuracy and precision.

Summary
Millions of containers arrive in international ports every year and it is clear that a large proportion of them represent a significant hazard. Employers have a duty of care to protect their staff and court cases have found in favour of workers that have suffered ill-health from container gases. It is inevitable therefore that the amount of testing required will continue to increase so there will be a greater emphasis on speed, risk reduction and cost.

Portable FTIR gas analysers substantially reduce the amount of equipment required to test a container, but more importantly, the technology enables the simultaneous analysis of a large number of target compounds, which improves the effectiveness of the assessment and reduces risk to staff. The technique is also much faster and avoids the use of disposable equipment.


Implementing automated machinery safety

19/02/2013

One of the most significant trends driving automation relates to machinery safety and how the integration of technologies is key to advances in this area. Here, Nigel Dawson, Festo GB’s Product Manager for Electric Drives, surveys interesting developments making life easier for design engineers.

While the subject of machinery safety is not new, it continues to play a key role in machine and plant construction. But, there are many different approaches and a great deal of uncertainty amongst machine builders in how to handle these issues and what degree of complexity and cost they need to go to, to adequately minimise risks; it isn’t surprising many machine builders and end users seek advice and support.

A fully integrated approach that monitors both the axis of a machine and allows safety-related clamping or braking is the best, safest solution!

A fully integrated approach that monitors both the axis of a machine and allows safety-related clamping or braking is the best, safest solution!

In applications that are not protected by physical safety guards, but where personnel can come into direct contact with plant components, the Machinery Directive 2006/42/EC indicates systems must provide adequate risk reduction through integrated safety functions.

In many cases an overall safety concept, requires the monitoring of moving axis, as well as safety-related clamping or braking, depending on the expected conditions. In higher risk applications two independent channels are required. In the past, machine builders would often design in their own safety solutions that took the safety switching device and wired in the STO, or Safe Torque Off, function. Frequently servo motor have been replaced by a motor and brake combination in vertical applications.

Now there are several problems with this approach; they do not take into account all the possible failure states – a coupling assembly breakage or slippage or a broken toothed belt in a parallel mounting kit could render the brake useless. These faults could still allow the carriage and load to fall, causing damage or injury.

A fully integrated approach that monitors both the axis of a machine and allows safety-related clamping or braking is the best, safest solution and this is exactly what Festo’s electric axis EGC unit does, it has an optional second channel displacement encoder and one or two channel clamping unit. The mechanical system can be monitored by both a motor encoder (first channel) and the linear displacement encoder (second channel) mounted on the axis providing two channel monitoring.

The axis can also be specified with single or dual-channel clamping units EGC-HPN which are suitable for holding a position, collision protection and, due to their emergency braking features, enhance safety in any vertical axes, for example, those which are typically used in lifting and stacking applications.

Of course legislative safety is not the only use of such features as additional encoders and mechanical braking systems. External encoders offer direct input into Festo servo controllers to allow unsurpassed positional repeatability on mechanical axis. For instance, it is now possible to achieve 10 micron positional repeatability on a standard belt drive when configured with a simple low cost encoder option, giving machine builders belt drive performance with ballscrew accuracy. Similarly vertical loads can be held safely for long periods without the need for high current usage on servo motors, by choosing a simple mechanical clamp option.

With today’s safety standards it is a more complicated task for designers to gather together all of the data from different manufacturers to calculate and document their own designed safety solutions. The Festo EGC axis provides a cost effective solution for compliance to the requirements of the Machinery Directive in a neat and self contained assembly and a single part number. Festo provides information on a wide range of electric and pneumatic safety functions through a Safety Guidelines manual that can be downloaded from their website and distributed through the Machinery Safety Alliance seminar program.