Standards, Competence and Training
16 March 2012
In addition to the very specific installation and use standards for trace heating, gas detection and miners’ caplights, there are five standards in the IEC 60079 series. These are all about what happens to equipment after it is dispatched from the factory. History confirms that most accidents relate to the use of these standards, rather than the standards of construction.
Expulsion of hot gases through a flamepath
People are the weakest link in the chain and training alone does not prove competence.
As David Doig of OPITO wrote in the January edition of HazardEx, talking of a survey of oil majors: “There is a mixed approach to competence with various views on what it is and how it is measured. More attention needs to be paid to the outcomes of training programmes.”
Certainly training is a major component leading to competence, but it is not the only one, and an examination directly following a training course is mainly a measure of short-term memory retention of the training material. A failure confirms incompetence but a pass cannot confirm competence.
The concept of competence should focus on what is expected of an employee in the workplace, and their ability to perform, rather than on the learning process. Competency will either build or degrade throughout a work period according to how the learnt skills and knowledge are applied in the workplace.
Area Classification – IEC 60079-10-1/-2
The formulae for determining Zones and extent of Zones are quite complex and difficult to work with. It is necessary to apply engineering judgement as a reality check. The ability to apply that judgement only comes with building competence. Even the definitions for Zones 0, 1 and 2 and for Zones 20, 21 and 22 need to be read with a degree of understanding applied at the most basic level.
Selection and Installation – IEC 60079-14
The section on cable glands alone can test the competence of many people, but there are other parts that could be easily overlooked if the fundamental technical background is not understood. The standard contains very strict “anti-obstruction” requirements relating to the flamepaths on Ex d equipment. Yet there is plenty of evidence that this requirement is either ignored or overlooked. An understanding of the distinctive two ways in which the escaping gasses are cooled to avoid ignition of the surrounding gas-air mixture will ensure the requirement is never overlooked.
Incorrect maintenance leads directly to danger
The primary cooling relates to the pressure drop along the path. Everyone who has pumped up a bicycle tyre by hand will understand the application of the universal gas law PV/T = C – that is that the hand holding the top of the pump feels the heat caused by the compression. The flamepath behaves exactly the same but in reverse, so the gasses are cooled by the change in pressure (and definitely not by the cooling effect of the surfaces of the path, which makes a minimal contribution).
The secondary cooling is caused by the speed of the escaping gasses being sufficient to entrain the cooler external gasses into the stream, thus further cooling the escaping gasses. This secondary cooling may or may not be necessary, depending on the exact configuration of the flamepath.But other than for screw-thread flamepaths, the installer of equipment will not be able to tell. Placing an obstruction close to the exit of the flamepath can interfere with this process and can trap the hot gasses in a confined space with the external atmosphere, leading to an external ignition.
Inspection and Maintenance – IEC 60079-17
The standard describes three levels of inspection: visual; close; and detailed, and different skills are needed for each. There is also a need to understand the difference between maintenance and re-design. Any re-design (i.e. replacement of a part of an equipment by a different part) needs very careful consideration, and the standard draws attention to the need for a review process with appropriate level of authorisation. It is also very clear that the person performing the maintenance is not allowed to sign off his own work as having been inspected.
In the case of the switch in the Ex d enclosure shown, three people should have been involved in the acceptance: the individual who accepted the re-design; the operative who actually made the modification; and the inspector who signed off his work. Can we conclude that all three were ignorant of the need not to drill a hole in the back of an Ex d enclosure or, more likely, can we conclude that the maintenance was not carried out in accordance with the procedures in the standard?
Repair and Overhaul – IEC 60079-19
This standard is the foundation of the IECEx Service Facility Certification Scheme which has been running since 2007, with now 60 certified repair workshops in the scheme. It is important to realise that much of the standard is concerned with mechanical service and reclamation, such as metal spraying, as well as the electrical aspects. As well as competence in these specific techniques, the staff still need to understand the fundamentals of the explosion protection techniques, or they may replace high tensile fasteners with those less able to withstand the explosion pressures.
Recent discussions in the IECEx ExTAG Committee have revealed that sometimes it is the plant owners who try to put pressure on the repairers to subvert the standard requirements because they do not understand the reasons why certain activities are restricted.
An inferior fastener can fail
IECEx Certificate of Personnel Competence
This scheme was devised to meet the needs of industry as a partner to all five of the “user” standards. The foundation is a three-part approach to verifying competence: first, a requirement for training related to the activity: second, a requirement to log and validate work experience putting the training into practice, and third, a separate examination concentrating on the application of the knowledge and skills in the workplace.
Of the 10 formal Units of Competence, six involve a practical element as part of the examination and some involve practical calculations. All involve both multiple choice questions and short-form answer questions. Although one person has actually sat and passed the examinations for nine units in one week, this was the exception and it would be normal for an individual to sit between one and five units, to match their current employment experience.
For full information, see www.iecex.com
The experience from Australia is interesting, where a number of engineers have obtained the IECEx Certificate of Personnel Competence in response to concerns about the effectiveness of the existing Australian scheme, where the training establishments are in charge of the examinations. They have attended Baseefa examination centres in both the UK and Singapore, so have clearly seen the value of the IECEx scheme over and above their national scheme.
Singapore is proving important as an examination centre and not just for Australians, as both Petronas and Shell Brunei have also put their weight behind the scheme. In Europe, much of the interest follows from the support for the scheme from Total.
By the time this appears in print, there will be approximately 100 individuals with IECEx Certification. This may not sound a lot but, after the first three years, there were about 100 product certificates issued in the original IECEx Scheme. The total now exceeds 10,000. A similar exponential expansion is envisaged in the field of Personnel Competence, with a possible total of between 50,000 and 100,000 certificates issued in a 10 to 15 year period.
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