How do plants protect operators from Arc Flash?

‘Arc Flash’ occurs when electric arcs are formed during fault conditions in switchgear: TAS is conducting a survey to assess the level of knowledge and establish ‘Best Practice’ for worker protection.

Judith Hackitt CBE (Chair of the Health and Safety Commission) said on the 29th April 2008, at a conference on major hazards in London, entitled “Leading from the top – avoiding major incidents” – that the HSC would like to see UK companies sharing ‘good practice’ on known hazardous events, and circulating these between themselves – both internally within companies and with the wider industrial community (

TAS Engineering Consultants are one of very few companies in the UK who regularly conduct and advise on electrical arc flash protection and potential hazards for UK based clients.

There is quoted to be a huge amount of interest in this subject at the moment throughout the UK Electrical Engineering and Safety Management Community, and as a leading member of this community TAS wish to take the lead to establish the ‘Best Practice’, and take the steps towards avoiding any incidents.

Arc Flash occurs when electric arcs are formed during fault conditions in switchgear.

The arc can pose a significant risk to both personnel and plant, and injuries can be caused by the intense thermal radiation, pressure (blast) waves, molten material and noxious gases produced by such arcs.

Serious burns and fatalities have both occurred as a result, in the UK.

A separate effect is that switchgear can be damaged and be out of operation for significant periods, causing plant shutdowns.

TAS, through their MD John Maplesden, have presented papers on the subject at various events, such as the HazardEx series of conferences, and published relevant papers.

Now TAS wish to take the lead in discussing this important area and assessing the level of knowledge about Arc Flash hazards in industry, to understand what plant operators are doing to mitigate the possible dangers, and protect their workforce (such as by use of the proper PPE, Personal Protective Equipment).

The objective will be to create a network that can share good practice amongst the user community.


Initially the survey is being conducted by mailing the questionnaire to UK engineers in industries that are higher power users, (the mailing will go out in June) and there is also an on-line survey form on the TAS website,

Respondents from overseas are welcome, but their experiences, attitudes and knowledge of arc flash hazards may be reported separately, to see and identify where differences exist compared to UK practice.

Following the collation and analysis of the information, the aim is to share the results and point to the best ‘Good Practice’ on such electrical safety intelligence within UK industry.

The results will be presented by TAS in the form of:.

* White papers and articles submitted to industry publications – sharing findings and identifying the proposed future ‘Best Practice’.

* Presentations at conferences, seminars, industry association meetings, road shows and peer forums/fora.

The planned closing date for the survey is 20th June.

Please fill in the survey form, if you use high voltage or high current switchgear: ‘Nil’ returns and requests for more information are as important as complex knowledgeable answers: the survey results will be totally anonymous.

The Sensor + Test Exhibition at Nurnberg, 2008

The Sensor + Test Exhibition in Nurnberg featured many of the normal industrial sensors seen in UK exhibitions, so this report concentrates on some of the developments seen with optical sensors.

Many of these were directed at gas analysers, as have been reported before.


PAS-Tech Gmbh from Hamburg featured their Photo-Acoustic Spectroscopy (PAS) systems , which uses a diode laser to excite the molecules of low concentrations of contaminant gases (dipoles).

The difference between the PAS system and conventional spectroscopy techniques is that PAS-Tech use the acoustic or pressure waves produced by that vibration to detect the small concentration of the contaminant.

Basically the system uses a microphone to pick these signals out.

PAS-Tech was founded only in 2002, but has an impressive array of medicinal and industrial applications, offering gas sensitivity down to 0.001ppm: see

* MKS.

MKS is a US origin company well known for mass flow controllers and systems, although they are not yet sending information to Processingtalk.

However they also offer a more conventional FTIR based gas analyzer range: the MultiGas 2030-HS is a high resolution gas analyzer designed to monitor automobile, diesel and catalyst combustion exhaust at 5 Hz sampling frequencies.

This can monitor 20 gases or more, simultaneously, at this sampling rate.

MKS produce several residual gas analysers for monitoring anything left over from CVD processes, etching or ion implantation systems.

See MKS on

* HBM.

HBM are one of the major strain gauge manufacturers in the world, producing over 5Million gauges a year, and a lot of associated equipment.

At Sensor + Test 2008 they showed their recent fibre-optic developments in strain gauge sensors.

Basically the optical fibre is treated to create a Bragg grating in the section of the fibre that is to be strained.

This section is provided with a carrier that enables the sensor to be bonded to the substrate or test piece in exactly the same way as a conventional strain gauge.

When the fibre is then strained, or stretched, the spacing in the Bragg grating is also stretched.

Laser light transmitted down the fibre is reflected by the Bragg grating at a specific frequency where the wavelength is equivalent to the grating spacing: by tuning the laser frequency, for example over the range 1510-1590 nanometres, the position of the peak of the reflected power gives a measure of the grating width.

The typical width of the peak to be measured might be 0.2nm, so several, say up to 10 peaks, can be monitored by one swept frequency source.

This means that a single optical fibre can carry 10 separate Bragg gratings, making one fibre monitor 10 strain points: See

HBM have developed the electronic units to monitor these different peaks, and can even offer combined optical/electrical strain gauge monitoring systems.

They are building operational sensors for commercial use: tests have shown the fibre-optic cable to easily monitor large strains, such as 7500 um/m, without any hysteresis or ageing, over 2500 cycles (when a conventional strain gauge lasted 100 cycles only): the operational life is expected to exceed 10Million cycles.

This makes the technique useful for monitoring composite materials, plastics or carbon fibre constructions, for example in aircraft components.

The optical strain sensors have also been used on bridge structures, such as stone bridges, and metal bridges: the fast response time allows such sensors to monitor the flexing of the bridges when trains pass over them at different speeds, accelerations etc, turning the sensors into low frequency vibration or flex sensors.

In such outdoor situations there is a possible need for temperature compensation of the optical fibre expansion, or alternatively a second optical sensor, not subjected to a strain, is positioned next to the strained sensor, to provide the zero reference.

But if the flexing amplitude is the only measurement of interest the zero line is irrelevant.


Not quite optical, Sonotec, from Halle near Leipzig, presented their multiple ultrasonic products for through the pipe wall monitoring of liquid level, whether chemical, pharmaceutical or liquefied gases, leakage detection, pipe-cleaning Pig position monitoring, pump protection, bubble detection in liquids and so on.

For the applications you cannot do with optics, Sonotec maybe can do them with ultrasonics:


At EasyFairs Solids this year, Minsterport in the UK showed the Rembe particulates flowmeter, able to monitor powder flows to 0.25% accuracy: Rembe was again at Sensor + Test, showing off the same C-Lever flowmeter, which has successfully been applied to chalk, titanium dioxide, cereals, pigments, sunflower seeds and dried sludge – monitoring flows between 50 and 2000kg/h, on particle sizes up to 10mm.

OK its not quite optical, but you can see how it works, and it provides an electronic measurement of the flow.


Conglomerates + Corporate style: Halma + Spectris

Two major UK groups, Halma plc and Spectris plc, have adopted a “hands-off” approach over the public image of their subsidiaries: these groups own some most interesting process industry suppliers.

There are interesting differences in the corporate style adopted by various of the conglomerates, ie large businesses that own or acquire multiple subsidiaries, in the process industry supply sector.

Many of these you will be aware of, where the multiple subsidiaries and factories are operating under one major company name, such as is the case maybe with ABB and Emerson Process Management.

There are then two other styles of operation adopted: the first is typified by two UK owned groups, Halma and Spectris, and the second is seen in two US company groupings, GE and Thermo Scientific.

The UK style is typified by the operating companies within the group continuing to operate independently, and using their own company names and identities, and outwardly at least retaining an appearance of being an independent company.

They retain their own sales engineers and sales responsibility, so that you might be unaware that they have any link to other companies in the industry.

They also possibly retain the drive and enthusiasm that comes from a small close knit company, and, maybe, gain more customer loyalty therefore: but these are just possible outcomes, no-one can prove it.

The US style is identified by strong corporate branding, and the virtual disappearance of the original or acquired company name.

The result is that sometimes the Exhibition stand seen under the new company name might be displaying products bearing no relation to those that you identify with the company.

The big company gains a corporate identity, with the possible benefits that arise from that.

Whether either style is the “Best” way to run an operation depends on the overall objectives, but the groups now formed in Halma and Spectris are very successful technologically, and apparently in business terms.

But possibly they are also both beginning to adopt a more prominent or corporately forceful role via their main websites, which is an interesting development of this corporate style.


The Halma listing of their major product lines includes the following process industry related companies:.

1) Fire detectors: each year Halma companies sell over 2 million detectors to customers in 60 countries.

The smoke and heat detectors are based on ionisation, thermistor and infrared sensors, under the company names of Apollo Fire Detectors, Fire Fighting Enterprises and Air Products and Controls.

2) Gas detectors are produced by Crowcon Detection Instruments, and include portable units to protect the lives of lone workers and fixed gas sensors to monitor entire industrial sites.

3) Water treatment systems: the main Halma treatment systems are non-chemical, based on UV technology, used for disinfecting drinking water, waste water, swimming pool water and also to create the high purity industrial water supplies used in food processing and electronics manufacture.

Various company names are used, possibly based on the geographical history of the operations: these include Hanovia, Berson Milieutechniek, and Aquionics.

4) Water leak locators: For the water distribution industry, Halma make the world’s most advanced instruments for detecting and locating leaks in underground drinking water pipes.

This technology allows water providers to detect any underground problems, and increase supplies in drought areas while cutting production and distribution costs.

Relevant company names are Palmer Environmental, Hydreka SAS and Fluid Conservation Systems.

5) Other water industry suppliers: In this area we have Halma Water Management, which seems to break the mould of typical Halma companies by using the Halma name! But Halma list this under the Halma Corporate offices, and their products include those produced by Radcom (Technologies).

Other water industry suppliers in the group include Perma Pure (Gas dryers and humidifiers for fuel cell, medical, scientific and industrial use) and Palintest (Instruments for analysing water and measuring environmental pollution).

6) Machine safety systems: Halma leads the world in machinery safety products called interlocks.

These electro-mechanical devices are fitted to hazardous machinery to protect workers from injury or death.

Many of these are reported, under the company names of Castell Safety International and Fortress Interlocks (plus also Netherlocks).

Klaxon Signals (Audio/visual warning signals for fire and industrial security) is also a member of the Halma Group.

7) Spectrometers: Halma also claim to be the world leader in miniature spectrometers, via Ocean Optics.

These are optical sensors and analysers which measure the quantity and spectrum of light to reveal what things are made of and to measure the amount of compounds present in a sample.

They can be used as sensors in atmospheric pollution monitoring systems.

8) Other Process industry suppliers in Halma.

From their corporate website there are several further process industry and water industry suppliers within the group: one of these is Smith Flow Control, manufacturing process safety systems for petrochemical and industrial applications, and Elfab, who produce pressure sensitive relief devices to protect process plant.


The Halma history is interesting: the company origins were in Asia in 1894.

As The Nahalma Tea Estate Company Limited, it operated in Ceylon (now named Sri Lanka): the company later switched to rubber production and in 1937 became the Nahalma Rubber Estate Company.

During the 1950s the Sri-Lankan government nationalised many of the island’s businesses, including the rubber industry.

In 1956 the Nahalma Rubber Estate Company became Halma Investments.

The company ended its connections with rubber and its role changed to an investment management and industrial holding company.

Starting in 1972, a series of acquisitions was made of mechanical, electrical and electronic engineering companies: successful management has generated strong organic growth.

2007 sales were around GBP355M.


Our second example of this UK style of business is Spectris.

This company was founded by Sir Richard Fairey in 1915 as the Fairey Aviation Company.

Initially manufacturing seaplanes, the company achieved renown during the 1930s and 1940s with its aircraft.

Following the rationalisation of the aviation industry in the 1950s, the company diversified and established its non-aviation engineering capabilities in areas such as marine, energy and filtration.

During the 1990s the company concentrated on building its electronics sector, making a number of acquisitions.

In 1997, the company acquired Burnfield, of which Malvern Instruments was the most significant company.

Then Servomex was acquired in 1999.

In July 2000, the acquisition of the four instrumentation and controls businesses of Spectris AG of Germany for GBP171m was the largest ever made by the company and marked an important strategic addition to their instrumentation and controls business.

The reshaping of the group was marked with the change in name to Spectris plc in May 2001.

This business was transformed from being in UK aviation and engineering to a provider of innovative technology for the improvement of customer performance worldwide.

The Spectris claim is that their products help customers to improve product quality and performance, increase productivity and yield, and reduce downtime and waste: sales in 2007 were around GBP668M.

A smaller group than Halma in terms of number of companies owned, there are 13 individual businesses in four segments, and many of these businesses will be well known to readers of the INSIDER, presenting interesting new products under their own names.

1) Materials Analysis.

Malvern Instruments: Analytical systems for materials characterisation, from bulk powders to nanomaterials and macromolecules.

Particle Measuring Systems: Microcontamination monitoring systems for ultraclean environments and manufacturing processes.

PANalytical: X-ray analytical equipment for industrial and scientific applications.

2) Test and Measurement.

Bruel and Kjaer Sound and Vibration: Transducers, sound level meters and analysers for sound and vibration measurement.

HBM: Load cells, transducers, strain gauges, signal conditioning and data acquisition systems, weighing electronics, test and measurement software and services, calibration laboratory and high-precision instruments.

3) In-line instrumentation.

Beta LaserMike: Non-contact, laser-based dimensional measuring and flaw detection; ultrasonic dimensional gauging.

Bruel and Kjaer Vibro: Machine condition monitoring systems and maintenance services.

BTG: Instrumentation, metering and doctoring technology for the pulp and paper industry.

Fusion UV Systems: Ultraviolet light processing technology for curing photosensitive inks, coatings, and adhesives.

NDC Infrared Engineering: Infrared, X-ray, Isotopic and microwave sensors for on-line measurement and control of moisture and composition of foods, tobacco, pharmaceuticals, building products and minerals and film thickness, coat weight and moisture in the converting, extrusion, paper, non-wovens and other web processing industries.

Servomex: Gas analysers, gas analysis systems and transducers.

4) Industrial Controls.

Microscan: High speed industrial barcode scanning and decoding instruments.

Red Lion Controls: Operator interfaces, signal conditioners, temperature controllers, counters, rate indicators and panel meters.