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Silencing offshore noise issues

Published:  06 April, 2016

Health and safety remains a critical aspect of any offshore operation, with companies across the oil and gas industry placing an added emphasis on ensuring the welfare of their workers in recent years. Operating in such hazardous environments presents an abundance of significant safety challenges, none more so than noise, as Lee Nicholson, managing director of Wakefield Acoustics explains.

On a daily basis, offshore workers are exposed to loud turbines, helicopters and mechanical noise for prolonged periods of time. Although strict rules governing the use of hearing protection are already in place, noise induced hearing loss remains a serious problem for the industry, with some 600 cases of hearing loss reported annually in the Norwegian oil and gas industry alone.

Globally, noise-induced hearing loss continues to be one of the most prevalent irreversible occupational hazards in the offshore oil industry. In fact, research from the Health and Safety Executive (HSE) estimates that over 30% of workers in the offshore sector are exposed to noise levels in excess of the upper action limit. While it is predicted that 120 million people worldwide have disabling hearing difficulties.

Norwegian Petroleum Safety reports indicate that the reported number of hearing damage and tinnitus cases is growing, with noise induced hearing loss being the one of most frequent workplace injury/illness reported

While noise is not a specific problem to the offshore industry, the particular characteristics of the industry, with extensive noisy equipment and processes located on a single platform, present particular industry specific noise control challenges. New fields, often in deeper waters are continually being accessed. These often require equipment operating at higher pressures and temperatures, thereby creating even more difficult and noisy conditions in which to operate.

Although progress has been made within the sector, noise exposure remains a major challenge for the industry.

Prolonged exposure to excessive noise levels has the potential to create a wide range of long term and often-irreversible health impacts including permanent hearing loss, tinnitus, cardiovascular diseases, sleep disturbance, stress, brain impairment and mental health issues.

The effects for business should also not be underestimated where the requirement to limit noise levels often leads to lower productivity levels, with a need for increased staffing or shorter hours of operation.

At a time when the offshore oil and gas industry is seeking to access newer, deeper, more complex fields along with a projected growth in Floating, Production, Storage and Offloading (FPSO) facilities, the challenges remain significant and the opportunities for improved occupational health of staff and overall business productivity greater.

Noise Legislation

Regulatory changes are also helping the industry to make significant steps towards safer practices. The key pieces of legislation applicable to noise within offshore installations within the UK are the Control of Noise At Work Regulations 2005 implemented under EU Directive 2003/10/EC) and HSE publication OTR2001/068 which outlines technical recommendations for the way in which noise and vibration should be taken into account in the design of offshore platforms. Exposure limits within the Norwegian sector are in line with EU legislation and NORSOK S002 sets similar standards to OTR 2001/068 for living and working areas.

The Control of Noise at Work Regulations 2005 reduced the upper and lower action levels by 5 dB from 90 and 85 dB (A) in the previous directive to 85 and 80 dB (A) and introduced a new exposure limit of 87 dB (A).

Equally fundamental, the latest regulations move away from a focus of earlier legislation on assessment, quantification of exposure levels and consequent hearing protection, to a philosophy of controlling noise at source wherever possible.

Within the offshore industry the move to access deeper fields, coupled with the close proximity pumps, compressors, valves and pipes and noisy hand tools on a space constrained single platform, means that specific expertise is required to accurately diagnose and treat platform noise control issues. This is an area in which Wakefield Acoustics works particularly closely with customers - understanding, diagnosing and implementing practical noise control solutions.

Over the course of the company’s 35-year history it has developed extensive knowledge of treating complex multifaceted noise problems, each with its particular set of challenges. Work over the last 10 years within the North Sea fields has involved innovative solutions to complex noise issues across a variety of applications.

Addressing noise in offshore applications

Given the increasing demand for higher performance, and the fact that increased power output from offshore machinery leads to higher noise emissions, machinery manufacturers are looking at packaged acoustic enclosure options to mitigate the noise risk and save space.

Wakefield Acoustics has experience with a number of solutions ranging from on-skid mounted localised acoustic enclosures, on-skid localised acoustic screening, and both skid mounted and deck mounted fully encompassing acoustic enclosures, designed to be accessible by personnel for equipment maintenance purposes.

The requirement for skid mounted acoustic enclosures is becoming more widespread, and as such operators require these enclosures to be designed with the highest level of safety in mind.

In line with specification, packaged enclosure options include hazardous area compliant ventilation systems and filtration, hazardous area lighting and emergency back-up lighting, complete with full electrical fit out and terminated at internally or externally mounted junction boxes, as well as fire and gas detection and suppression systems.

Working within the space constraints, which are common to these types of installation, can be particularly challenging. Whilst not losing sight of stringent working environment specifications in relation to personnel, all the ancillary safety equipment and features must be tightly packaged within each enclosure.

In certain applications it is necessary to consider accidental loads in conjunction with environmental loads. In relation to the design of acoustic enclosures, the most critical accidental loads to be considered in most offshore applications are blast loads. Through the process of design and utilisation of Finite Element Analysis (FEA) methods for both static and transient structural analysis, we are capable of manufacturing enclosures that are designed to meet the specification requirements for the most onerous of blast load incidents.

These designs must not only consider the inherent noise of the equipment and the desired maximum noise levels required in different areas of the structure, but also the logistical and spatial limitations in terms of access to, from and around the rig. Hence the correct design and selection of acoustic products in particular housings for plant items is essential. This must be achieved first time to avoid the serious implications of non-compliance of specifications and the excessively costly nature of retro fitting. There is no margin for error and with this in mind we have tested the performance of our range of acoustic enclosures to BS EN ISO 11546-1:2009, as required by BS EN ISO 15667 ‘Acoustics – guidelines for noise control by enclosures and cabins’.

With improved health and safety remaining at the forefront of the offshore oil industry, and noise reduction becoming a major factor in this, the requirement for oil and gas companies to adopt noise control solutions beyond conventional personal protective equipment (PPE) has never been more critical. Add to the mix, renewed legislation, which places an added emphasis on ensuring employee welfare, and that requirement becomes even more obvious. Noise therefore will need to be addressed increasingly through the design and development of offshore platforms.

Johan Sverdrup oil field contract

Wakefield Acoustics recently secured a contract for the Johan Sverdrup oil field, located on the Norwegian continental shelf. This multi-million-pound project comprises Wakefield Acoustics’ engineers designing and installing 17 high specification acoustic enclosures, intended to significantly reduce noise levels on the offshore platform.

The Johan Sverdrup field is one of the largest oil discoveries ever made in the region and is expected to generate between 550-650 barrels per day at its peak over the course of the next 50 years.

The challenges inherent with the supply of noise control solutions to such a highly-productive offshore application were vast. Due to extensive health and safety demands, Wakefield Acoustics designed the enclosures to withstand the client specified blast loads in the event of an explosion.

The packaged enclosure options also incorporated safety features, which are typical for such hazardous area applications, with hazardous area compliant ventilation systems and filtration, internal lighting and emergency back-up lighting, removable sections for regular and major maintenance requirements, as well as fire and gas detection and suppression systems.

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