TECHNICAL AND ORGANIZATIONAL METHODS AGAINST VIBRATION

Pursuant to §5 of the Regulation of the Minister of Economy and Labor of August 5, 2005 on health and safety at work associated with exposure to noise or mechanical vibrations (Journal of Laws of 2005, No. 157, item 1318) it is the employer's duty to eliminate the source of occupational risk related to exposure to mechanical vibrations or limiting this risk to the lowest possible level whilst taking into account available technical solutions and scientific and technical progress.

Activities aimed at limiting exposure to mechanical vibrations and related risks should include technical and/or organizational solutions that can be implemented in a given situation, which must be strictly correlated with the applicable legal requirements.

Effective methods of minimizing exposure to vibrations require adherence to a proven and commonly accepted system of actions. According to it, the measures taken to reduce the risks associated with mechanical vibrations should be in accordance with the following scheme:

1., Elimination of the hazard through its reduction at the source.

2. Reduction of vibrations through the method of propagation.

3. Personal protective equipment.

4. Organizational solutions.

Elimination of the risk factor by its reduction at the source of formation is a technical solution that produces the best results, but is not always possible for technical or economic reasons.

The reduction of source vibroactivity can be achieved by interfering with their construction such as minimization of clearances, improvement of balancing of rotating elements, elimination of mutual impacts of cooperating elements and their proper assembly, proper fastening of machines to the ground - foundations, etc.). Most of the activities of this type are usually only at the design and production stage of the machine, however, systematic technical inspections, replacement and adjustment of wearing parts of the device can be performed by the user.

In the ordinance of the Minister of Economy of October 21, 2008 on essential requirements for machinery and safety components (Journal of Laws 2008 No. 199 item 1228) it was specified that:

1. In the instruction attached to the held or hand-guided mobile machines information should be given on the frequency-weighted r.m.s value of acceleration for hand-am vibration considering two possible cases. These being, when the R.M.S value of acceleration (1) exceeds 2.5m/s² and (2) is below 2.5m/s². In the absence of an appropriate method for determining the effective value of vibration acceleration, the manufacturer should determine based on which methods and under what conditions this value has been determined.

2. In the case of a moving machine, the manual should contain measured or calculated values on the basis of measurements of identical machines:

1. The frequency-weighted r.m.s value of acceleration transmitted to the hand-arm system, (1) if this value exceeds 2,5 m/s² and (2) if this value does not exceed 2,5 m/s². This information should be included in the instructions.

2. The frequency-weighted r.m.s value of acceleration transmitted to the body as a whole - foot and buttocks, (1) if this value exceeds 0,5 m/s² and (2) if this value does not exceed 0,5 m/s². This information should be included in the instructions.

The manufacturer should also provide information regarding the operating conditions of the machine during the time of measurement. The results from the tests should be included in the instructions along  with a description of the measurement method used. If harmonized standards are not used, vibration should be measured using the most appropriate method for the machine.

Proper use of equipment, as intended by the manufacturer, ensures high impact on the emission of vibration from the source. This includes the proper installation and use of vibration isolation and damping elements that are components of the machine equipment. Thus, the operational manual should be consulted to ensure that the equipment is being operated in its intended use.

One of the technical methods that is eliminating vibrations on the path of propagation consists in adding between the source and the protected object various elements separating, damping or isolating vibrations. A typical example is the addition of dilatation between machine and equipment foundations and the environment, using vibroinsulating materials in various forms (mats, pads, special vibro-shock absorbers), as well as by the use of personal protective equipment (anti-vibration gloves). Vibration damping is also obtained by using multilayer structures or covering vibration elements with damping layers. As a result of these applications, there is a decrease in the amplitudes of steady-state vibrations, a rapid decay of free vibrations and the suppression of waves propagating in elastic elements. Depending on both the device and vibration damping strategy used, various materials may be used on the bituminous substrate, polymers, elastomers, rubbers, organic glasses and felt, etc.

Vibro-shock absorbers are the most commonly used elements that limit transmission of vibrations from devices/stationary machines. The effectiveness of vibro-isolators depends not only on their design but also on their proper selection (mainly to the mass and frequency of the machine). Standard vibro-isolators are usually made of elastic elements in the form of, for example, steel springs, as well as rubber, pneumatic or hydraulic elements absorbing and insulating vibrations.

Another technical method of minimizing vibrations is connecting additional mechanical systems to vibrating objects, such as dynamic vibration absorber, which allow to limit the amplitude of vibrations. Because vibration eliminators require tuning them to a specific frequency (narrow frequency range), such solutions are used for machines and stationary devices generating steady-state or near steady-state vibrations.

The most modern and effective technical methods of limiting or eliminating mechanical vibrations include active and semi-active vibroisolation systems. In active systems, additional, properly controlled sources of extortion are used. However, in the semi-active control systems, the parameters of antivibration elements (eg. elasticity) are used. Spring elements are commonly used to limit exposure to whole-body vibration transmitting to the body of the worker through buttocks and back of the seat (seat vibration insulation).

Personal protective equipment against hand-arm vibration (anti-vibration gloves) should be used when it is not possible to eliminate the risk associated with mechanical vibrations using alternative  solutions or as an auxiliary element. The effectiveness of anti-vibration gloves depends largely on the frequency but also on the strength of the grip and feed force exerted by the operator.

Anti-vibration gloves assume that they do not damp vibrations at low frequencies (below 30 ÷ 50 Hz), which cause unfavorable changes in the osseous-joint and muscular system of hand operators of vibration tools, but often effectively limit vibrations at higher frequencies which, according to research, have a significant impact on the appearance and development of the vaso-nerve form of the vibration syndrome. This is extremely important, because among the recorded cases of the vibration syndrome, its vasomotor form is very common. The effectiveness of protection of anti-vibration gloves depends not only on their design but also on the conditions in which they are used (the nature of the vibrations emitted by the tool and the exerted force by the operator), which is why it is very important to choose them properly.

It should be noted that the use of anti-vibration gloves not only reduces the vibrations transmitted from tools to the operator's hands, but also protects hands against low temperature and moisture, which intensify the effects of vibrations, accelerating the development of the vibration syndrome. Therefore, the use of anti-vibration gloves even in cases where they reduce vibrations to a very small extent is perfectly justified.

Technical methods of limiting the risk of mechanical vibration include also automation of technological processes and remote control of vibration sources. These methods allow employees to move away from areas threatened by mechanical vibrations, reducing the risk of health loss due to vibrations.

Organizational solutions aimed at limiting exposure to mechanical vibrations include:

• Shortening the time of exposure to vibrations during the working day.
• Making use of breaks at work and rotation at workplaces.
• Designing jobs and placing jobs in such a way as to limit the number of exposed workers, or to limit the simultaneous impact of multiple sources on the employee.
• Moving people who are particularly sensitive to vibrations to work in other positions.
• Employers should undergo training on exposure to vibrations.
• Controlling factors that favor the development of the vibrating unit.

Activities aimed at shortening working time, using breaks and rotation at workstations are aimed at reducing the daily exposure to vibrations. Reported to employees and employers as part of the training (more information about the training is in the section on employer's responsibilities), it avoids mistakes and inappropriate behaviour that may increase the risk related to the risk of vibration. Controlling factors such as low temperature, excessive humidity or physical load of the body helps to minimize the risk of vibration syndrome (these factors contribute to the development of this disorder).