Noise mitigation in refineries and chemical plants has been, and still is, a major concern for plant operators looking to ensure the health and safety of their employees. Although significant progress in understanding industrial noise and effective control has been made, the problem continues to present a challenge in the industry. Robert Lomax, Sales Director of Wakefield Acoustics, explains how one chemical plant is already taking a proactive approach to implementing noise management and mitigation measures within its plant.
With noise control and environmental legislation becoming more stringent and employee health and safety remaining at the forefront of all processing practices, ensuring that noise is effectively mitigated has become a key concern for process plant operators across the chemical processing sector.
Controlling noise in chemical plants presents distinctive and complex noise and acoustical challenges, due to the large number of potential noise sources in-situ and the size of most facilities. The methods required to process or manufacture chemicals, typically on a large scale, employ a large spectrum of mechanical machinery which has the potential to emit excessive noise. Equipment such as centrifuge machines, mixers, high-pressure pumps and valves, as well as the associated pipework, can combine to generate noise that is potentially detrimental to the health of employees and disruptive to the local community.
There is a myriad of noise sources within a typical chemical plant. Identifying key, major contributors to the excesses within the plant is fundamental to reducing the noise impact on site and the environmental impact of plant in the surrounding community. For a large chemical manufacturing plant operator, with a complex plant operation, the process of early identification and noise mitigation proved central to their drive for reduced on-site noise.
Sound advice for chemical plant
Having undertaken a detailed noise survey across the production space, the company’s ESH department identified that a high level of noise was being experienced by operators across the entire workspace. The in-depth site analysis identified the Sedicanter, in particular, as the major source of noise within the facility. In fact, such were the levels of noise on site, that the entire facility had become a mandatory ear protection zone when the machinery was in operation, which should normally be regarded as a last resort.
Although hearing protection reduced the operators’ noise exposure, it also presented several operational issues, including the necessity for regular hearing assessments, instruction and training on noise, and the requirement to display signage in relevant high noise zones. Keen to lessen dependence upon ear defenders, and reduce employee noise exposure from the plant to as low a level as was reasonably practical, the client sought the expertise of noise control specialists Wakefield Acoustics to outline effective noise mitigation options.
The noise levels with the Sedicanter in operation were recorded at 91.3dBA at a distance of one metre, with readings of approximately 83dBA being experienced in other areas of the production space when the machine was in operation. The company was aware that, if left untreated, the noise levels emitted from such equipment could pose a significant risk of hearing damage for operators and maintenance personnel.
With this in mind, the client required that noise levels were reduced to 80dBA or less across all areas of the facility. The chemical plant manager also understood the importance of specifying a solution which would allow maintenance and servicing access throughout the bn lifetime of key machinery, to prevent problems arising, and enable staff to put faults right and ensure equipment is working effectively.
As with the majority of machinery of this type, careful consideration had to be given to the number of different paths in which noise emanated. In the case of the Sedicanter, noise originated in several areas including electric drive motors, hydraulic power packs, the cover to the rotating machine and the material outlet feeds. This being the case, a number of noise control options were considered, with the agreed outcome being a fully ventilated acoustic enclosure to house the entire plant.
Specialised acoustic enclosures
The acoustic enclosure was designed to house the entire machine, including associated power packs. An integrated ventilation system was installed to extract warm air generated by the machine, which was discharged into the main factory area. In order to avoid air recirculation, the inlet and outlet ventilation openings were installed at opposing corners of the enclosure.
As with many acoustic enclosures, maintenance and servicing access remained a major consideration during design and installation. In this instance, two double leaf access doors were incorporated into the enclosure structure to allow personnel access for general maintenance. As the machine was serviced via an existing overhead maintenance beam, the acoustic enclosure was designed with a hinged end-wall panel section and two removable roof sections, permitting easy access to the main screw mechanism and other key components. All removable components were fabricated with lifting points and certified lifting eyes were supplied.
To support routine cleaning processes, which entailed equipment being regularly washed down, the enclosure was manufactured with a 304-grade stainless steel framework. The main acoustic panels were formed with a galvanised steel outer skin with a high specification powder paint finish, and were lined on the inside with 304-grade stainless steel perforated sheet to prevent corrosion.
Whilst the enclosure was designed to offer a high level of noise reduction, one of the company’s concerns was the ability to view the machinery during normal operation when stood externally to the booth. In order to overcome this, a number of vision panels were installed into the side walls of the enclosure, all designed to ensure the resultant noise criterion was achieved.
Through careful diagnosis and the implementation of the acoustic enclosure, noise levels across the chemical plant were reduced to 80dBA or below, in line with the company’s objectives, thus negating the requirement for hearing protection to be worn by operatives.
What’s more, the plant’s staff were able to maintain effective access and maintenance schedules following the installation.
To implement best practice and comply with the most recent noise legislation Chemical producers have turned to the noise mitigation technologies as a way to reduce on-site noise and protect employee health and safety. In the UK, the most recent noise legislation is under The Control of Noise at Work Regulations 2005, whereby the upper and lower daily noise exposure action levels have been reduced by 5 dB from 90 and 85 dB (A) in the previous directive to 85 and 80 dB (A) respectively.
Equally fundamental, the 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. There is also an increased emphasis on controlling noise at source wherever possible, a sizeable shift from the focus of earlier legislation on assessment and quantification of exposure levels, and recommendations for hearing protection.
More and more operators across industry, therefore, are considering ways to utilise noise mitigation technologies throughout their facilities on a greater scale. Forward-thinking chemical plant operators are going a step further, looking to transform their operations by building a culture of early identification and proactive prevention of noise at source.