Vibration Monitoring and Assessment

Introduction

Vibration monitoring is an essential part of day to day site management in the construction industry. Guidance notes on instrument placing and monitoring guidelines can be found  in monitoring standars such as;

• BS 5228: 2009 +A1 2014: Code of practice for noise and vibration control on construction and open sites – Part 2: Vibration.
• ISO 1996-1:2016 “Acoustics – Description, measurement and assessment of environmental noise Part 1: Basic Quantities and assessment Procedures”
• BS 7385 – “Evaluation and measurement for vibration in buildings – Part 2: Guide to damage levels from ground borne vibration” (1993);

Concern in relation to the potential for structural damage and nuisance caused by the use of explosives during quarrying and mining and also the use of piling equipment on construction sites with that of alternative heavy construction activity as always been high on the agenda of many construction companies, Local Authorities and the general public.

NVM Ltd can provide both the expertise and equipment to complete assessments to ensure all allowable and acceptable levels are at proposed or existing guidance levels.

Vibration Surveys

NVM Ltd can complete baseline / background monitoring and assessment surveys to establish existing vibration levels and help companies in their planning of pre–works monitoring programs. Complaints about vibration caused by traffic, pile-driving, and blasting are commonplace within the construction industries.

Recognised criteria for assessment of vibration impacts is peak particle velocity which is measured in three orthogonal directions transverse, vertical and longitudinal (x,y and z axes) this measured in millimetres per second (mm/s).

“On typical piling and construction projects at well - constructed properties - Typical values of between 10 mm/s and 30 mm/s can be tolerated without serious damage implications, however the figure with which the human body is sensitive to and capable of perceiving vibration levels at is much lower –human perception can be as low as 0.5 to 2 mm/s in the vertical direction which is the main reason why complaints are commonplace.”

Construction Applications

• Structural vibration monitoring
• Prediction of ground-bourne vibration
• Airover pressure from large scale demolition projects risk analysis
• Piling monitoring programs

Quarries and Mining applications

• Measurement and assessment of HGV and rail movements
• Determination of safe working distances
• Residential monitoring programs
• Blast monitoring
• Quarry and IPPC license procedures

Occupational Surveys - HAV and Whole Body Assessment

• Guide To Hand Arm Vibration

New legislation regarding the protection of employees and employers in the field of vibration is now in force in the Republic of Ireland.

The Control of Vibration at Work Regulations 2005

This requires employers to monitor and implement, if necessary, strategies to ensure that their employees are not exposed to vibration levels that may cause pain, discomfort or adversely affect their lives outside of work, or impede their ability to perform their duties properly.

The groups who may be at risk are;

• Employees who are exposed to Hand Arm Vibration through the use of hand held tools like for example grinders, impact drills, cutting tools, etc.
• Employees who are exposed to Whole Body Vibration through the operation of heavy plant and machinery such as diggers, dumpers, excavators, fork lift trucks, grass cutting machines, etc.

NVM Ltd offer a comprehensive testing and reporting service which conform to the ISO 8041:2005 and is in accordance with the Control of Vibration at Work Regulations 2005.

Summary of HAV

Hand-arm vibration syndrome, once commonly known as vibration white finger, is a type of repetitive stress injury that can result in permanent damage to your fingers, hands, and lower arms.
It can develop after prolonged exposure to hand-held, vibrating tools. Because this describes many different types of machinery, hand-arm vibration syndrome, or HAVS, can affect a wide variety of people and professions.

HAVS can occur due to the use of several different types of equipment, including:

• Jackhammers
• Concrete vibrators and levelers
• Chainsaws
• Needle guns
• Chipping tools
• Polishers
• Sanders

Over time, the vibrating can affect your circulation, nerves, and other tissue. Thus, there are three different indicators of HAVS.

First, you may notice a condition similar to Raynaud's phenomenon. This is where people derive the nickname "white finger." With this symptom, exposure to cold weather or cold objects can make your fingers turn a very stark white.

Next, they turn blush as they lose their oxygenated blood supply. Lastly, circulation rapidly returns, turning fingers bright red.

Next, vibrating tools can also interfere with your nerves. This can leave you with painful tingling as well as numbness in your fingers. The numbness can disrupt your ability to handle fine tasks, such as fastening buttons.

Lastly, the vibrations can also cause damage to your muscles, bones, and joints through your fingers, hands, and lower arms. This may cause you to suffer from aches and pains throughout your arms.

In 2005 the Health and Safety Authority (HSA) estimated that 13% of workers in Ireland are exposed to HAV in the workplace, and about 40% of those who are exposed are exposed to levels of vibration where there are clear risks of developing disease.

HAVS is preventable, but once the damage is done it’s irreversible and the cost to employees and employers who do not take action could be very high.

The regulations introduced Action and Limit Values for HAV and action to reduce the level of personal exposure is required if these values are reached or exceeded.

Exposure Action Value (EAV)

This level is set at 2.5m/s² averaged over an 8 hours working day, where employers are required to put in place technical and organisational measures to reduce exposure.

Exposure Limit Value (ELV)

This level is set at 5.0m/s² averaged over an 8 hour working day, where employee exposure is not permitted to exceed.

Summary of WBV

Have you ever tightened your grip on the steering wheel, dashboard or seat anticipating the next pothole or next obstacle? Over a prolonged period of time, this type of exposure takes a toll on the body. Occupations that require driving long distances or operating heavy equipment expose workers daily to low-frequency vibrations generally less than 100 Hz. Exposure to these vibrations can cause serious physical problems ranging from chronic back pain to nerve or organ damage.

Research on truck drivers and heavy equipment operators indicates that intense, long-term whole-body vibration increases risk to the spine.

Whole-body vibration is caused by twisted sitting postures combined with vibration. The combination increases stress and load on the neck, shoulder and lower back. To compensate for the discomfort from vibration, drivers should change their position. However, if the assumed position is incorrect, the stress may be increased.

This often occurs when operating equipment which causes constant physical vibration such as occurs when driving off-road vehicles or forklifts.

Whole-Body Vibration Exposure

As vibration is transmitted to the body, the effect of the vibration can be amplified by factors such as body posture, type of seating and frequency of the vibration. Individual human body parts have their own resonant frequencies. This is why after a long drive we continue to feel as if we are still moving even after the vehicle has stopped. Vibration from engines can agitate the body to the point of causing micro fractures in the vertebrae, disc protrusion, nerve damage and acute lower back pain.

Short-term exposure vibration causes only small physiological effects such as a slight degree of hyperventilation and increased heart rate. Vibration also causes increased muscle tension from voluntary and involuntary muscle contraction. Muscles become tense in order to dampen the vibration. Examples of this type of tension would be having your foot fall asleep while pressing the accelerator pedal or experiencing a tingling sensation in your hands from gripping a steering wheel too tightly.

• Low-frequency vibrations of moderate intensity can induce sleep.

• Higher frequencies have the opposite effect.
• Vision can also become blurred because of the movement of the image on the retina.

With advancements in transportation, we often travel longer distances at faster speeds. Whole-body vibration research is now focusing on determining the vibration and exposure levels that initiate physical and mechanical changes in the body.

Exposure Determination

To determine possible whole-body exposure to workers, ask the following questions:

• Is the worker exposed to whole-body vibration while sitting in a vehicle?
• Does motion and/or vibration cause the worker to hold on to the steering wheel or another support for stability while standing or sitting?
• Does the worker complain of pain, discomfort or fatigue in the back, buttocks or feet because of jolts or vibration?
• Does the worker bounce when the vehicle is in operation?
• Is the worker in an awkward position?
• Is the seat on the vehicle properly secured and maintained?

Control Measures

If your workers are exposed to whole-body vibration, engineer the problem out by installing newly designed seats and suspension systems. If that is not practical, the next best thing is to institute work practice controls to reduce or minimize the vibration.

To control the amount of whole-body vibration, the following work practices and administrative controls can be implemented:

• Reduce travel speed to reduce vibration levels;
• Require rest breaks to avoid constant continued exposure.
• Obtain information on equipment vibration and recommended maintenance schedules from the vendor;
• Minimize the vibration created between floor ramps and vehicles by maintaining ramps and dock levellers;
• Improve vehicle suspension and use vibration isolation or dampening for seating to reduce vibration transmission; and
• When appropriate, workers should incline the backrest up to 10 degrees and use lumbar support.

Summary

Whole-body vibration most often affects occupations that require prolonged driving.

Research shows that continuous exposure to vibration can be detrimental to the body. Any intervention such as isolating the driver, using lumbar support and armrests or repairing roads can help reduce whole-body vibration. The key is to take action by eliminating or reducing the exposure to whole-body vibration.