Health check

5 mins read

Everyone involved with notified hazardous areas should be well aware of the legislation and ACOPs, and the seriousness of their duties. But part of that includes more audit than some may realise, says Brian Tinham

The term 'hazardous areas' means different things to different people, but to engineers in the oil and gas, petrochemicals and chemicals industries, it signifies plant designated as having some level of fire or explosion risk. Other more general health and safety hazards, both operational and occupational, may well exist too. However, the real deal here is understanding the risks posed mostly by liquids, vapours, mists, gases and combustible dusts – and then preventing catastrophic incidents by considering alternatives, ensuring proper containment, eliminating ignition sources and/or mitigating the human, environmental and plant impact should the nightmare happen. Beyond COSHH (Control of Substances Hazardous to Health 2002) and REACH (Registration, Evaluation, Authorisation and Restriction of Chemicals 2006), primary legislation here comprises COMAH (control of Major Accident Hazards 1999, amended 2005) and DSEAR (Dangerous Substances and Explosive Atmospheres Regulations 2002). COMAH implements the Seveso II Directive, and is policed by the HSE (Health and Safety Executive) but also the Environment Agency (and its counterparts in Scotland and Wales), and covers named dangerous substances, both toxic and explosive. Plants (mostly chemical processing and/or storage) are deemed COMAH sites if they hold or process quantities greater than published thresholds – with those at the high end classified Top-Tier. In the spirit of goal setting, the regulations then require that operators take all measures to prevent major accidents involving these substances, while also limiting the consequences to people and the environment, if they occur. Note, however, that even non-COMAH sites holding small quantities of dangerous materials might find themselves in trouble, if they fail to adhere to good practice, as established under COMAH. Meanwhile, DSEAR requires that workplaces involving potentially explosive atmospheres be classified into zones, based on the assessed scale and frequency of explosive atmosphere risk. As the HSE website puts it, they must then be 'protected from sources of ignition [mechanical as well as electrical] by selecting equipment and protective systems on the basis of the categories set out in the Equipment and Protective Systems for Use in Potentially Explosive Atmospheres Regulations 1996 [EPS]'. As for the details concerning those zones and equipment categories, these are defined under ATEX (ATmospheres EXplosive – actually two directives) and supported by a set of national ACOPS (approved codes of practice). For the record, ATEX 137 (Directive 99/92/EC: the Workplace Directive) covers health and safety protection for workers at risk from explosive atmospheres, while ATEX 95 (Directive 94/9/EC: the Equipment Directive) addresses equipment and protective systems. These lead on to definitions of appropriate equipment protection concepts, such as flameproof Ex d, increased safety Ex e, intrinsically safe Ex i, pressurised Ex p and non-incendive type n. None of this should be new to anyone involved with hazardous area protection. Nevertheless, there remain some very important issues for plant and factory managers, as well as engineers at every level, to wrestle with – and these mostly concern currency. Few would dispute that, when process plants and their control systems were designed, installed and commissioned (following operational studies, risk assessments, etc), the hazardous area implications must have been taken into account. How rigorously and how accurately may be a moot point, but they passed muster. However, what about today? The plain fact is that change happens. Some change is planned, and here the expectation of the HSE, the Environment Agency et al will be that competent persons carry out formal 'management of change' programmes. Note that these should apply no matter how seemingly insignificant the alteration – for instance, installation of a higher performance pump to improve plant throughput. Clearly, it is important that the implications – in terms of containment under COMAH, but also classification under DSEAR – are considered and resolved. And, in effect, much the same applies to retrospective surveys of equipment in place prior to the enactment of DSEAR. It's all about informed and consistent audit. But, while larger COMAH sites have mature processes in place to ensure this happens, there may be question marks over some smaller plants – particularly those operating just outside the COMAH regime. Importantly, however, some change is unplanned. For example, plant deteriorates over time (sometimes inevitably, occasionally avoidably) at rates dependent on the environment, materials of construction, substances being processed, production rates etc. Hence the importance of inspections at whatever frequency matches the duty holder's obligations, particularly when it come to containment. Yet, as Stuart Pointer, team leader for mechanical engineering at HSE's CEMHD (chemicals, explosives and microbiological hazards) division, puts it: "70% of the sites for which we have accumulated data since 2010 need to make improvements, and the most pressing concern is the ongoing integrity of their primary containment." Quite simply, the issue of ageing plant and its implications – not only concerning vessels and pipework, but also safety-critical mechanical equipment, such as pumps and compressors – is not getting the level of management attention, leadership or resources it deserves. As a result, all too often, inspection, analysis and maintenance are falling short. And that is potentially very dangerous. Pointer cautions engineers and managers to ask themselves whether they ought to be satisfied with their arrangements, in terms of plant inspection, where hazardous areas are concerned. And his colleagues in CEMHD's electrical, control and instrumentation, and process safety departments would offer similar advice. His number one exhortation: "Make proper use of the findings from your inspection programme. Don't treat your report like an MOT certificate to be filed away. All too often, when we investigate incidents, we see findings on reports from two or three years beforehand that link directly to what has now happened. Inspections cost a lot of money and unless you take that next step of ensuring you read and understand the implications, then you haven't maximised that investment." You've got the bit of paper, but you haven't heeded what it's telling you about the plant, says Pointer. "Maybe something has changed – and perhaps that's led to faster degradation of a vessel, which needs attention. But then you need to consider what else might have changed out there. By putting the effort in up front, and meeting your legal obligations, you will head off potential incidents." Beyond that, he suggests revisiting the largely hidden issue of corrosion under insulation. "It's quite a big problem. There are still sites out there where it has never even been considered. Engineers and managers need to make a judgement as to how much insulation needs to be removed – for example, from carbon steel pipework in the open – to give them a fair understanding of its state. But, if they don't, it can come and bite them unexpectedly." That's the last thing you need in hazardous areas. Useful publications SAFed (the Safety Assessment Federation) and EEMUA (the Engineering Equipment and Materials Users' Association) published guidance in 2012 on inspecting plant and equipment, taking account of the problems of ageing. 'Mechanical Integrity of plant containing hazardous substances: a guide to periodic examination and testing', which is endorsed by HSE, establishes good practice in maintaining the primary containment boundary. Next up will be a document tackling working with third party specialist plant inspectors. The publication, which is being worked up through the Chemical and Downstream Oil Industries Forum, facilitated by HSE, will provide guidance on the keys to successfully contracting third-party expertise – including defining roles and responsibilities, checking for appropriate competencies and ensuring that in-house knowledge is adequate to understand and challenge the significance of findings. This publication is due to be launched by the end of 2014. Automation systems When it comes to automation systems designed to operate machinery and/or processes in notified hazardous areas, additional measures are required. And – although far from applicable exclusively to plant with explosive atmospheres – these are contained in the European standards concerned with functional safety of electrical, electronic and programmable systems (E/E/PS). Principal among these are IEC EN 61508, which mostly covers safety protection in machine automation, and IEC EN 61511, which describes the measures necessary for safety-related process control. Each, however, introduces key concepts of safety integrity levels (SIL) and performance levels (Pl) – with automation systems specified and tested for robustness to match levels commensurate with the adjudged risk, using standard HAZID (hazard identification) and HAZOP (hazard and operability) studies. And you'll find that PLC system manufacturers, such as ABB, Hima-Sella, Mitsubishi, Rockwell and Siemens, all offer safety-related PLC options as a starting point.