Safety during grinding

Everything you need to know about noise, dust and PPE

Grinding with handheld and stationary machines is a central process used in metal processing for stock removal, forming or surface finishing. Grinding work can be carried out with a wide range of tools and machines, which involve different degrees of risk, depending on the application and abrasive used.

Because: High speeds and temperatures are involved – a grinding disc, for example, usually runs at up to 11,000 revolutions per minute. This results in speeds of almost 300 km/h at the edge, and overall process temperatures of more than 800 degrees.

As with all industrial processes, “acute” safety problems, such as burns or cuts, can occur due to device failure, but also due to human error. In addition, there are possible long-term health hazards that can also occur with the routine use of abrasives; these include the effects of noise, dust or excessive hand-arm vibration.

In the following, we will briefly explain which of these safety aspects must be taken into account when grinding and what precautions must be taken (to counter them). – For example, with products from safety technology manufacturer and VSM partner Dräger. The focus is also on how new, more efficient products from VSM can reduce the risks associated with grinding. The fact is that VSM’s products can help customers make their employees’ work stations safer, quieter and, all in all, significantly more user-friendly. Read how below.

Grinding dust and its extraction

Dust is generated when grinding workpieces, on the one hand due to the removal of stock from the workpiece, and on the other hand due to the wear of the abrasive itself. If the dust gets into the air, there is a risk of skin contact – or even worse: The dust can be inhaled.

At first glance, dust usually seems harmless and really more of a nuisance, since it makes cleaning necessary. However: Dust is not just annoying; it can actually become dangerous for users, even though the lungs can generally handle smaller concentrations of dust. Ultimately, various factors influence whether and to what extent respirable dust is harmful. The type of dust, the duration of exposure to the dust, and the composition and size of the so-called airborne particles are decisive. These, in turn, are primarily influenced by the workpiece and the material properties of the abrasive used.

Dust is the cause of many occupational illnesses. Extremely fine grinding dusts, some of which are not even visible to the naked eye, are considered particularly harmful to health. Because the finer the particles, the more easily they can be inhaled via the respiratory tract. And the finer the abrasive, the finer or smaller the dust particles. A fine dust particle with a size of 1 µm, for example, takes up to seven hours to fall to the ground – which means it can be inhaled over this period of time.

There are two categories of dust: A-dust and E-dust. E-dust refers to all “inhalable dust”. A-dust, on the other hand, refers to the proportion of respirable dust that actually reaches the air sacs of the lung (the alveoli), since it is too small to be retained in the nose or throat. There are strict limits to be observed for both types of dust: Since 2001, the limit value of 10 mg/m³ has been in force for E-dust. The limit value for the particularly harmful A-dust, which finds its way into the alveoli, was recently lowered further to 1.25 mg/m³.

Learn more about grinding dusts

Health hazards

Small particles can be deposited in the nose, mouth and throat – or in the lungs, via which they can enter the bloodstream. The deeper the dust penetrates into the lungs, the more dangerous it is: Very fine dust particles from 0.1 to 1.0 µm can penetrate particularly far into the lungs. If they settle there and stick to the alveoli, because large amounts of dust are inhaled over a long period of time, the natural cleansing process of the lungs can come to a standstill.

Such inhaled dusts that no longer dissolve in the body can cause diseases. These range from respiratory tract inflammations such as chronic bronchitis, asthma and COPD to so-called pneumoconiosis such as silicosis, allergies and cancer.

Particularly dangerous situations can arise when aluminium is processed. This is because aluminium dust is considered extremely hazardous when inhaled, and it can even cause an explosion under certain circumstances – i.e. with a sufficient ratio of oxygen from the air in combination with an ignition source. Work stations where aluminium is ground must therefore be equipped with an extraction system that is in continuous operation.

Safety management

Use appropriate abrasives: The finer the dust, the less noticeable it is, making it potentially more hazardous. The goal should therefore be to produce as few chips and particles as possible, or at least to produce chips and particles that are larger in size – the grit size of the abrasive and the type of stock removal it achieves are decisive factors here. Self-sharpening VSM abrasives such as the VSM CERAMICS series or VSM ACTIROX with their geometrically shaped abrasive grain cut particularly cleanly and effectively through the material and thus produce larger chips that remain in the air for less time. The consequences: The shorter dust exposure times mean reduced pollution of the work station. The abrasives themselves also help reduce dust generation, as they have a long service life and ensure high stock removal rates.

Extraction and ventilation: Extraction of the dust is not only necessary when grinding aluminium, where it is also mandatory, but also when grinding other dusts if the dust load cannot be minimised by technical means. “If the machining task does not allow this, the dust must be completely captured at the point of origin, extracted, and safely removed from the working area”, stipulates the German Association for Accident Insurance (DGUV). There are various different technical approaches to this – they range from encapsulation within a completely enclosed working area that is connected to an extraction system through to semi-open systems with dust-extraction grinding tables, and integrated direct extraction devices in the tool.

PPE: In addition to using ventilation and suitable abrasives, users must be equipped with appropriate personal protective equipment (PPE). In the case of inhalable dust, this involves suitable eye and respiratory protection (at least FFP2) as well as a protective suit and gloves.

Safe workplace design

Noise during the grinding process

In a metalworking workshop, there is a lot going on – after all, mechanical means and high speeds are required to remove any unevenness, burrs, etc. from the workpiece surfaces. All this creates considerable background noise in the form of sound pressure. In other words: Grinding machines are always noisy: From the drive of the machine and the coolant pump through to the workpiece conveying system and any incoming and outgoing workpieces, or vibration noises that originate from the workpiece itself (such as in the case of larger tanks), there is a veritable concert of noise originating from a wide range of sources. Not forgetting: The abrasive belt or grinding disc itself.

Hand-arm vibrations

Grinding machines vibrate during use. One problem that occurs, especially in professional grinding, is the vibrations that affect the operator’s hand-arm system. This hazard occurs primarily on bench grinders or when using bonded abrasives, but also when using hand grinders such as angle, disc and orbital grinders as well as hand-held grinding machines in continuous industrial use.

Grinding seminars in Hanover – just enough theory plus lots of practice

Grinding greases and oils

A major problem, especially when machining non-ferrous metals such as aluminium, is rapid clogging of the abrasive. This is due to the fact that aluminium has very low strength and thus a high tendency to smear and cause material to build-up on the cutting edges during grinding. For a long time, it was common practice to add grease or grinding oil to keep the abrasive belt unclogged for longer, especially when grinding aluminium. Grinding oil and grease reduce the friction between the abrasive and the material, which generally improves durability and extends the service life of the abrasive. They also act as a cooling lubricant. The biggest and most obvious disadvantage: Extensive cleaning of the machine, tool, workpieces and the entire working environment is necessary, which has a negative impact on productivity.

Learn more about safe work stations

Noise emission: Health hazards

This overall noise can place quite a strain on the machine operator, even when ear protectors are worn. There is a risk of ear pain or even hearing damage such as tinnitus or permanent noise hearing loss.

In principle, anything above an average noise level of 80/85 dB is considered hazardous to health. The determination of the specific risk of noise exposure – the so-called risk assessment – must be carried out by a qualified person. If the daytime noise exposure levels determined in this way exceed the above-mentioned values, certain legally prescribed protective measures must be taken. These include informing employees about the dangers, providing and ensuring the use of hearing protection (from 85 dB), marking and technically demarcating noise areas, and taking mandatory occupational health precautions. The maximum peak sound pressure level must not exceed 137 dB.

Noise emission: Safety management

"The actual noise level during grinding depends, among other things, on the grinding method, the type of grinding machine, the workpiece, and the ambient conditions", states the DGUV . Accordingly, it recommends, among other things,

technical measures such as encapsulation or partial encapsulation of the machine
the use of silencers on pneumatically driven machines
also equipping colleagues in the vicinity with eye and ear protection.

The choice of abrasives also has a decisive influence on noise exposure. For significantly smoother/quieter operation than with conventional, simply coated abrasives, VSM ILUMERON, for example, is a good choice. Why is this? The fully-coated, very even surface of the abrasive lies flat on the workpiece – thanks to the even surface topography of the contact zone between the abrasive and the workpiece. But VSM ceramic grain abrasives such as ACTIROX and the VSM CERAMICS series also significantly reduce noise exposure as a whole – because they grind faster and therefore for shorter periods. Lower levels of operating noise mean better protection and much more relaxed and fatigue-free working. And employees are even more productive, of course.

Hand-arm vibrations: Health hazards

Such prolonged exposure to vibrations transmitted by the tool can have major health effects. These include, for example, circulation disorders, nerve function disorders, vascular damage, and bone and joint damage. The best known is the so-called white finger syndrome, which refers to irreversible blood flow disorders in the fingers caused by prolonged vibration. The risk of contracting the aforementioned diseases increases even further when working in the cold.

Hand-arm vibrations: Safety management

Companies are obliged under the German Noise and Vibration Occupational Safety Ordinance to minimise the risk associated with vibrations. The regulations specify a strict daily vibration exposure value that should not be exceeded: For example, in the case of very high exposure levels, the limit value at which protective measures must be taken is reached after just a few minutes.

The health risks due to too many vibrations can be limited by a number of different measures. It is particularly important to choose a grinding machine that is as powerful as possible, has low vibrations, and can complete the grinding work in the shortest possible time. Among other things, the DGUV recommends using devices with additional systems for vibration reduction or with balance compensation and vibration-reducing handles. An autobalancer is a particularly effective way of damping vibrations, since it optimises ergonomics. It also ensures that the specified maximum values are not reached until later, so that users can work with the device for longer. Choosing the right contact element, in terms of its hardness, also influences the vibrations.

In addition to the health benefits, an autobalancer also ensures more efficient grinding, since the grinding discs last longer and run times are shorter. The same applies to the selection of suitable abrasives: Those with high stock removal such as VSM ACTIROX prove to be particularly suitable, since they significantly reduce the strain on the user. They grind more aggressively and up to 200 percent faster than comparable grinding and fibre discs and require less contact pressure. This results in much shorter processing times and therefore less exposure to vibrations.

Other important measures to reduce vibrations are vibration-resistant gloves and the careful selection, adjustment and control of the machines used, especially with the aim of avoiding any imbalance.

Grinding greases and oils: Health hazards

Due to the high temperatures and tool speeds during grinding, the lubricant mixture of grease or oil, possibly supplemented by other cooling lubricants, is dispersed in the air as fine particles. These aerosols and invisible oil vapours are hazardous to health and can cause acute headaches, dizziness and nausea when inhaled. The long-term consequences can be more serious respiratory diseases such as cancer. In addition, grinding oil can cause skin irritation and allergic reactions if it comes into contact with the skin. Of course, eye contact should also be avoided, to prevent any irritation. Last but not least, there is even a risk of fire or deflagration if flammable oil mist/air mixtures are formed.

Grinding greases and oils: Safety management

PPE and extraction: To minimise these risks, users must take appropriate protective measures when using grinding oils and greases. This primarily includes wearing suitable respiratory protection masks to prevent inhalation of grinding dust and vapours. If certain workplace limit values are exceeded (10 mg of oil mist and oil vapour per cubic meter of breathing air), additional extraction systems and filtering separators are required. Gloves, special skin protection creams and safety glasses help prevent skin irritation and eye damage. It is also essential to keep the work area clean and always ensure that the grinding machine is properly maintained.

Use suitable abrasives: VSM ALU-X
Ideally, users should avoid using grinding oils and greases as much as possible. When it comes to aluminium processing, an abrasive such as VSM ALU-X is recommended, since it was specially developed for the requirements of grinding non-ferrous metals. The additional grinding-active layer and the semi-open coating of ceramic grain ensure noticeably reduced chip adhesion, so that with VSM ALU-X the work station can remain permanently free of grease and oil. “Grinding instead of cleaning” is the motto – with more productive machining in mind.

Personal Protective Equipment (PPE)

Personal protective equipment (PPE) is a central component of occupational safety, especially in industry and metal processing. It is intended to be used or worn by employees to protect them from hazards to their health and safety. In Germany, the provision of PPE by the employer and its use by employees is regulated in the German “Ordinance on Safety and Health Protection when Using Personal Protective Equipment at Work”. According to the German Occupational Health and Safety Act, the employer is obliged to provide its employees with protective clothing free of charge. Wearing the PPE is in the interests of each individual, even beyond their duty to do so, because it is ultimately about their own health.

Learn more about PPE

Health hazards

Wearing or using PPE is mandatory for good reason, because grinding metal involves a whole range of different hazards, which, for example, the DGUV and the Employer's Liability Insurance Association for Wood and Metal (Berufsgenossenschaft Holz und Metall) have clearly classified and summarised. On the one hand, these hazards include the physical hazards already mentioned above, resulting from noise or hand-arm vibrations, as well as hazards arising from substances and materials, such as vapours/aerosols and grinding dust.

On the other hand, there are additional hazards, such as mechanical hazards due to flyaway grinding disc fragments or to contact with the grinding disc, and thermal hazards due to hot workpiece surfaces after grinding, as well as fire and explosion hazards. Breakages or failure of the tool are particularly dangerous.

Safety management

Given the variety of hazards, it is not surprising that the safety-related regulations are comprehensive and very detailed. In the risk assessment for each work station or activity, professionals apply the so-called STOP principle: The aim is to first consider how the burden can be reduced by means of substitution (e.g. using other work methods or materials), technical solutions (e.g. structural shielding or extraction systems) or organisational measures (e.g. time limitations or training).

Only then should the remaining risks be further reduced by the use of personal protective equipment. The PPE is therefore intended to minimise the so-called “residual risk”.

PPE used during grinding includes

respiratory protection
eye protection
head protection
ear protection
and protective clothing including safety shoes, hand protection and skin protection.

All employees must be trained in the correct use of their PPE. Safety technology manufacturer and VSM partner Dräger.

provides a good overview of all products used as PPE when working on and with grinding machines.

The most important tips for safe handling of abrasives

Everyone who works with grinding machines must be aware of the associated safety risks. And this is important, since much of the responsibility lies with the operator of the tool. But employers are also responsible for ensuring the safety and well-being of their employees.

Most hazards can be minimised by users if they follow some key safety rules:

Use the right tools and abrasives for the application: This involves ensuring that the permissible speeds and maximum permissible speeds of the machine, backup pad and abrasive are compatible, for example, but also that the disc diameter matches the machine; otherwise the maximum cutting speed will no longer be correct.
Familiarise yourself with the tool, especially the start and stop behaviour, and do not modify it yourself. Observe the operating instructions and safety instructions and comply with the maintenance intervals.
Use only certified fibre discs, as these offer the highest level of product safety and user protection. In Germany, coated abrasives must comply with DIN safety standard EN 13743. All VSM fibre discs are also certified by the "Organisation for the Safety of Abrasives" (oSa) and are therefore particularly safe. The standards of the oSa are far higher than the legal framework requires.
Never use damaged or worn grinding discs: Also check new abrasives thoroughly for possible defects, e.g. transport or storage damage, before use. Observe the shelf life date!
Check discs for imbalance and readjust if necessary.
Tighten the fixing nut or flange nut correctly when clamping.
Use fibre discs only for grinding and not for cutting.
Always check to make sure that the workpieces are secured and fixed in place.
Always use PPE. Also avoid wearing loose clothing, open hair or jewellery, as there is a risk of these getting caught in the machine.
Maintain a safe working environment – also for third parties: If possible, work in an enclosed area and make sure that other people in the vicinity are not at risk from dust, sparks or noise.