For over 5 years, NVM has worked with an international engineering company on various projects, including foundation design and assessments of hyper and booster reciprocating compressors. Analyses include site soil characteristics, seismic response, liquefaction and soil structure, in addition to vibration and dynamic response anlaysis.
NVM are often called in to trouble-shoot problems with foundations (not of our design!), piping, vessels and machinery / structures of all descriptions and for all purposes. NVM are possible one of the few companies who have carried out the noise design and follow up survey for an LDPE (low density polyethylene) plant.
The management of a manufacturing facility requested NVM to perform an independent vibration survey and report results relative to whole body vibration criteria. The weaving and textile machines, situated on a concrete suspended floor, are in operation over a 24 hour period, seven days a week. Vibration of the floor is perceptible. The facts were established by direct survey –measurement of the vibration and the risk determined by comparison with limit criteria. In this particular case the floor vibration was found to be within safe limits in terms of hazard to employees.
Investigations were undertaken on site to determine the cause of a gas compressor’s high vibration levels, which was disturbing and damaging fittings around the package. Tests were carried out on the main components and piping at relevant, accessible locations and measurement data collected. Comparative data from two other machines on site was also collected to help determine suitable solutions for reducing the high vibration to acceptable levels. Various changes were made to the machine. A construction and modification process was used during which tests for natural frequencies and effects under running conditions were made to ensure desirable characteristics were being achieved.
Instructions were given by the client to predict specific vibration characteristics of a compressor foundation. Results for single point and double point models were calculated, vibration responses predicted using modelling software and the data presented.
This particular company provides solids control and waste management products and services to the oil and gas industries and has been a client of NVM for over 10 years.
NVM has carried out various vibration surveys, noise reduction trials, trial enclosures, acoustic intensity and noise testing on various types of machinery. Most recently, NVM provided noise and vibration tests on a shaker machine. Survey results are presented to the client in a clear and concise report.
NVM were instructed to undertake a vibration survey on a seawater cooling pipe line located offshore to Qatar. The works were conducted in two parts; offshore survey entailing measurements of the piping vibration, and office-based computer modelling of the pipe systems using finite element analysis (FEA). A formal report was produced containing information from the survey and the modelling with recommendations for changes needed to the pipe system supports to reduce vibration amplitudes.
Production within a wafer fab requires specific conditions, including negligible floor vibration. Any disruption to production involves high cost. A specialist principal contractor responsible for avoiding such disruption to production within a wafer fab from construction work on site required a vibration monitoring system. NVM began monitoring on site for specific time periods in 2009 and work is continuing.
A manufacturer of bridges and similar structures for erection and installation at sites across the UK requested a workplace noise survey with reference to the current Noise at Work Regulations (2006). Production involves the cutting and fixing together of steel and wood beams and plates.
NVM conducted the survey and reported the results, considering the current hearing protection in use and made recommendations as necessary.
This particular centre is used for a variety of events from exercise classes, drama classes to wedding disco parties, i.e., requirements ranging from speech to music. Complaints were made regarding the acoustic qualities.
The centre manager instructed NVM to perform acoustic tests and produce a report with recommendations. Reverberation times of the main hall were tested, in addition to background noise levels and noise from HVAC (heating, ventilation and air conditioning equipment). Recommendations were given in the report to improve the acoustic qualities of the hall for both intelligibility of speech and enjoyment of music.
An international engineering and environmental consultancy group required an independent structural analysis and response factor prediction for two floors in a newbuild project. A finite element modelling method was employed to identify the lowest natural frequency and modal summary data produced to assess results with limit criteria.
One of the worlds' leading suppliers of semi-conductor technologies was to install a new E-beam tool on an entablature floor in a clean room. Appropriate surveys were necessary to comply with the tool vendors' specification of acoustic, vibration and electromagnetic (EM) field limits for the floor environment in order to ensure proper function.
Measurement surveys were undertaken on site by NVM and the compliance of the data collected relative to the limit specifications reported. Surveys carried out included;
An assessment of noise and vibration levels in the accommodation and bridge areas of this tug were required to indicate practical noise control options.
NVM established the instrumentation on board the vessel following inspection and discussion of operating regimes. Monitoring was carried out during typical and simulated operations in the estuary. Subsequently, office based data analysis, an assessment to the various requirements, and consideration of practical options was completed.
New buildings were being constructed in the vicinity of a listed wall. The starting point was to understand the levels of vibration directly along/near the wall. The data collected was then used to assess the risk to the wall and provide recommendations to limit damage.
A leading global plant EPC constructor based in Korea, working on projects requiring hyper compressor systems wanted to enhance management understanding of the hyper compressor design procedure.
Training seminars at the company's Korean offices were undertaken by NVM over three days.
Complaints were made by public users relating to the level of floor vibration in the gymnasium/sports room due to activities in adjacent studio spaces. Vibration measurements were taken at the gym and studio floor areas relative to these concerns and an assessment performed. Recommendations were made for the current situation and further work which would be required to rectify the problem.
NVM has carried out work for private individuals who are disturbed by low frequency noise within their homes.
The threshold of hearing is the lowest sound level that can be heard; it depends upon the pitch or frequency and is strongly variable between different individuals. It has often been observed that, while individual hearing thresholds vary, one person can describe a sound at low frequency as “loud” while others cannot hear that sound.
NVM has investigated whether a noise is apparent, can be classed as a nuisance, and if it is most likely to be ground borne, i.e., vibration transmitted into and through the ground appears as noise within a property.
A specialist manufacturer of packaging required a noise survey report to comply with a Local Authority requirement in respect of their IPPC (Integrated Pollution Prevention and Control) permit.
Noise measurements were carried out on and around the site by NVM. Predictions of noise emitted to the surrounding area and the impact of that noise were facilitated using a computer based environmental noise calculation model. The relative noise impact at the local residential community was assessed and results compiled in a report for the consideration of the Local Authority. Noise levels are primarily assessed for impact according to BS 4142:1997 and World Health Organisation (WHO) guidance.
The client was concerned of movement in a 1950’s concrete framed building, notable vibration was experienced at the top (9thfloor) of the building. NVM were instructed to install suitable monitoring equipment and collect vibration data over a two week period. A formal report was produced presenting the main data collected, an analysis of this data confirming that unusually high vibration transients occurred and an assessment for the source of the vibration.
A noise impact assessment was carried out for a proposed mixed use site development, formerly an industrial site. The assessment took into account the proposed employment area, in addition to predicting the impact of both the prevailing environmental noise and assumed new industrial noise at the dwellings. Mitigation proposals were given for the worst case location for both internal and garden amenity.
The local authority required noise impact to be assessed in the planning process for two farm properties involved in poultry production. Background noise measurements were taken at the proposal sites. In addition, noise measurements were made at an operational site corresponding closely to the planned sites. NVM were then able, using a computer based environmental noise model to facilitate calculations, to predict noise at the surrounding area to the proposal sites and assess the impact of that noise in terms of BS 4142 and the WHO guidance criteria.