The costs of fitting d.c braking is approximately £125 for parts + £125 for electrical labour costs per motor, although this is dependant on the size of the motor that will be appropriate to the machine.
If the machine isolator is operated then power to the entire machine, including the braking unit, is cut off before the braking cycle has completed so the braking effect is lost. This has caused ‘run down’ accidents on machines fitted with DC injection braking when operators have approached the machinery for setting, not realising that the cutters were still rotating. It is therefore vital that the machine E-stop is always used to allow the braking cycle to complete before isolating the power supply.
The wiring to a d.c. brake should be such that actuating an E-stop, either a local or remote one, sends the d.c to the brake and stops the machine, i.e. this action is not prevented by how it is wired.
If the electrical supply to the factory/workshop etc. is known to be unreliable then to ensure that the d.c brakes still work either a battery backup or emergency a.c. supply of some sort should be considered (the d.c. brake control unit acts as a rectifier). However, in practice, although not unknown, battery backup is rare as it is very expensive, both financially and in space requirements and any battery pack would need to be able to meet the demands of all the machines that needed to be braked.
As long as the manual brake is maintained and works properly by quickly bringing the saw to a stop, there is no need to fit additional braking. If however the saw gets a lot of use and operators have been known not to use the manual brake then the risk assessment for the saw should be reviewed and consideration given to fitting electrical braking.
A spring or pulley system that returns the saw into a safe protected area can be fitted, as shown in cross-cut saw that will stop blade contact whilst it is running down. However, you will need to consider in your risk assessment how often the saw is used and by who. If lots of people use the saw and it has a long run down time, there may be a chance that another user pulls out the saw carriage not knowing that the blade is still rotating. If this is the case then braking may be a better option.
Many companies use trenching heads on radial arm cross cut saws. The increased weight and momentum of trenching heads causes longer run down times and this needs to be taken into account in your risk assessment (see previous question). If braking is to be used it should be able to cope with the heaviest blade in regular use and bring the saw to a complete stop before it cuts out. Note: all such tools must be ‘chip-limited’.
When working with thicker timber the machine feed table is often lowered sufficiently to allow ease of access to the cutters. The machines typically have a long run down period which increases the risk when making adjustments or clearing waste material.
The simple answer is yes as fixed machinery forms part of the electrical system.
Regulation 4(2) of The Electricity at Work Regulations 1989 requires that:
As may be necessary to prevent danger, all systems shall be maintained so as to prevent, so far as is reasonably practicable, such danger.
Guidance on this regulation is given in the Memorandum of guidance on the Electricity at Work Regulations 1989 - Guidance on Regulations, ISBN 978-0-7176-6228-9 (HSR25) which in summary says:
The following definitions are given in HSR25:
Further advice on inspection and testing of fixed installations can be found in:
The machine installer is required to carry out sufficient testing to establish that the safety precautions that are inherent in the machines design are satisfactory prior to it being used.
For, example if earth bonding between various parts of the machine has been disassembled then reconnected then it would be reasonable to test this to ensure it is satisfactory. This will apply to other aspects but would not necessarily mean a complete retest of the whole machine.
Where plug-in connections are used, it is not usual to retest electrical connections every time they are made or removed but this depends on the design and robustness of the plug/socket.
If however, these connections incorporate safety related control systems then some form of functional testing should be carried out. The range and type of plug connectors available is wide and varied, with some being more robust than others and may even incorporate key systems to prevent incorrect insertion. The quality of the connectors will therefore influence the level of testing required.
Four-sided planer moulders fall within the group of woodworking machines that require employers to carry out a risk assessment to find out if they need to fit brakes. However, Woodworking Information Sheet No. 38 PUWER 98: Retrofitting of braking to woodworking machines advises that the only reason for not fitting brakes would be if there was no added benefit. An example of this would be if the machine was in an enclosure with interlocked doors, where the interlocks prevented the doors being opened until the cutters had come to rest, using either a time delay or a stop/motion sensor.
Woodworking Information Sheet No.40 Safe use of four sided moulding machines provides good reasons for braking to be fitted:
In summary, four-sided planer moulders should normally be braked as they will then be safer and can be stopped and reset quickly so there will be less time lost. In addition, if a tool breaks, stopping the machine quickly will reduce the amount of damage that takes place.
On older machines fitted with a “wooden box” type enclosure simple locks and bolts will not prevent access to the enclosure with the machine running unless braking has been fitted and employees are trained and instructed to operate the brake and stop the machine before entering.
As a standard, machines should have an enclosure and braking should be fitted. In some cases interlocks on doors linked to the braking may also be beneficial. However, this will be dependant on the machines characteristics and system of work that must be employed with it, particularly for setting (see Q.3).
During setting it is a requirement for the heads to be running as the trial piece of material is ‘inched through’ the machine and the cutters are correctly adjusted.
Old machines may not have the remote setting /adjusting mode of newer machines and in some cases cutter adjustment must take place locally. Where an enclosure has been fitted the setter therefore has to work inside it. In these circumstances, if interlocks were fitted to the doors they would have to be closed to allow the machine to run. The setter would therefore be required to work alone inside the sealed enclosure and this could increase the safety risk. In addition, there will also be a higher exposure to noise and dust. This is why careful consideration is needed before fitting interlocks on the enclosure doors. Other options, such as a lock with controlled key access, may be more appropriate.
During setting operations it is very important that all cutters have been effectively guarded and this is normally achieved in two ways:
The normal expectation is that guards are fitted and closed during setting. However, on some of the older machines setters have reported that they need to be able to actually see the cutters during final adjustment and have been known to have the hood guards in the open position during setting. If this practice is identified during the risk assessment and confirmed to be an actual requirement then additional mesh guards must be fitted between the hood guard and the cutters. They should be designed to allow observation of the cutters during setting but be able to prevent any risk of contact with the cutters. They must also only be able to be opened or removed by a specialist tool. Care must be taken that the mesh guards are not detrimental to the extraction system and if so, they should only be fitted and used for setting and removed prior to normal machine operation.
Because of the dangers associated with setting it is essential that a machine specific risk assessment that considers safety and health issues has been completed. This should then be used to produce a safe system of work for the setting operation. The following topics should be considered:
Medium Density Fibreboard (MDF) is an engineered wood-based sheet material made by bonding together wood fibres with a synthetic resin adhesive. MDF is extremely versatile and can be machined and finished to a high standard. As a result, MDF has replaced solid timber as a low-cost alternative in a wide range of applications across industry.
The majority of MDF is mainly composed of softwood, although some brands may contain a higher percentage of temperate hardwood if this is locally available to the manufacturer. High levels of hardwood can be found in MDF board from outside the UK and Ireland.
The most common binder for boards intended for dry environments is urea-formaldehyde. Other binders may be used depending on the grade of board and its intended end-use. For example, melamine urea-formaldehyde, phenolic resins and polymeric diphenylmethane diisocyanate (PMDI) are generally used in boards that require an improved moisture resistance. PMDI binder is not formaldehyde-based and consequently does not emit any formaldehyde. The exact constituents of an MDF board will vary from product to product.
The atmosphere created by machining or sanding MDF board contains a mixture of softwood dust and hardwood dust (if it is present). In addition, there will also be free formaldehyde, dust particles onto which formaldehyde is adsorbed and potentially, the resin binder itself and its derivatives. However, the levels of free formaldehyde in boards made within the EU at levels of formaldehyde class E1 are thought to be insignificant. This is because at these levels the resin is fully reacted (polymerised) – see the questions below for information on standards and classes.
Under current legislation softwood dust, hardwood dust and formaldehyde are considered to be hazardous to health. Both softwood and hardwood dusts are known to be respiratory sensitisers and may cause asthma and other respiratory problems. Hardwood dust can also cause a rare form of nasal cancer.
Formaldehyde is classified in the UK, and in the European Union as a carcinogen and it carries the hazard statement ‘suspected of causing cancer’.
Because of the additional presence of formaldehyde in MDF the simple precautions detailed in questions below should be followed.
Formaldehyde is a simple but essential organic chemical that occurs naturally in most forms of life, including people, some foods we eat and trees. All products made from wood will therefore emit some naturally occurring formaldehyde. It is widely used in the manufacture of numerous products including shampoos, plastics, carpets, clothing, resins and glues etc.
A range of materials found in the home or workplace may therefore release formaldehyde. The US Consumer Products Safety Commission provides the following information on formaldehyde on their website.
Formaldehyde is normally present at low levels, usually less than 0.03 ppm,(parts per million) in both outdoor and indoor air. The outdoor air in rural areas has lower concentrations while urban areas have higher concentrations. Residences or offices that contain products that release formaldehyde to the air can have formaldehyde levels of greater than 0.03 ppm. Products that may add formaldehyde to the air include particleboard used as flooring underlayment, shelving, furniture and cabinets; MDF in cabinets and furniture; hardwood plywood wall panels, and urea-formaldehyde foam used as insulation.
Similar levels are quoted in the World Health Organisation (WHO) report WHO guidelines for indoor air quality: selected pollutants, published in December 2010. This states for buildings, some of which contain wood based panels, ‘levels on the average are less than 0.05 mg/m3 (0.04ppm) in homes and about half that in public buildings’. It is important to note that these levels are from all sources, not just building products.
MDF boards manufactured in Europe for construction purposes must meet the appropriate European standards. These are BS EN 622-1:2003 Fibreboards-Specifications - Part 1: General requirements and BS EN 622-5:2009 Fibreboards - Specifications - Part 5: Requirements for dry process boards (MDF). There are two European formaldehyde classes, E1 and E2, depending on levels of formaldehyde emission measured. The release of formaldehyde from E1 boards is less than 0.1 ppm (parts per million) and for E2 boards it is between 0.1 ppm and 0.3 ppm.
In Europe, the majority of manufacturers produce only low emission boards. There are some boards available on the market with extremely low formaldehyde emissions and some with ‘no added formaldehyde’, for example those using formaldehyde free binders such as PMDI, i.e. these boards will only have the naturally occurring emissions from the wood itself. Manufacturers from outside Europe may however produce boards that have higher emissions.
Wood based panels, such as MDF, that are used in construction should be CE marked according to – Characteristics, evaluation of conformity and marking. In complying with this standard, formaldehyde levels will have to be tested on a regular basis and a class will have to be declared (E1 or E2).
Other than compliance with the Construction Products Directive via CE marking (soon to be superseded by the Construction Products Regulation), there are no regulatory compliance schemes in the UK for emissions of formaldehyde.
There are a limited number of third party labelling schemes that do operate in the UK which specify amongst other things, maximum formaldehyde limits as part of their requirements. Such schemes include BREEAM (Building Research Establishment Environmental Assessment Method) for the assessment of buildings and for furniture products and the Furniture Industry Research Association ’FIRA Gold’ scheme.
Around the world there are certification and labelling schemes for products that can be specific to formaldehyde release, such as the Californian Air Resources Board (CARB) scheme or other schemes where a range of emissions may be considered, such as the AgBB scheme in Germany.
HSE is not aware of any countries in the world where MDF is banned.
Employers have duties under the Control of Substances Hazardous to Health Regulations 2002 (COSHH) to control risks to employees’ health arising from work activities. This means they need to ensure exposures to wood dust and formaldehyde are kept as far below the Workplace Exposure Limits (WELs) as reasonably practicable.
WELs are the concentrations of hazardous material in the air averaged over a specified time period – called the Time Weighted Average (TWA).
Two periods are used, long-term (8 hours) and short-term (15 mins) – the long-term representing a working day and the short-term to help prevent effects such as eye irritation which may occur after only a few minutes exposure.
The WELs for hardwood dust, softwood dust and formaldehyde are expressed in the number of milligrams (mg) of material in one cubic metre of air (m3). Levels of formaldehyde are also expressed in parts per million (ppm). The current WELs are:
To control exposures, employers should follow the ‘hierarchy of control’ set out in the COSHH Regulations. This means:
RPE should not be used as the only means of control as it should complement other control measures such as a dust extraction system. Where you need to use RPE you should:
RPE comes in three types FFP1 (4x protection), FFP2 (10x protection) and FFP3 (20x protection).
FFP3 is the most advisable type to have if you are exposed to high levels of dust and one combined with an organic vapour filter will also provide protection against any formaldehyde vapours that are present.
Chip limited tooling (marked as MAN meaning hand-feed) must always be used on a vertical spindle moulder, even if a demountable power feed unit is in use.
The Vertical Spindle Moulder is still required to be fitted with a ‘False Fence’ to reduce the gap between the fence cheeks, so as to ensure the following:
The bridge guard should be adjusted over the top of the workpiece as illustrated in Figure.1 of HSE Woodworking Information Sheet 17 not adjusted to the edge of the workpiece. The reasons for this are as follows:
Adjusting the bridge guard to the edge of the timber may appear to be safer as the blade is completely covered while the timber is passing over it, compared to the over the top method where the portion of blade not covered by the workpiece appears to be only partially guarded and is visible under the bridge guard and theoretically accessible. However, accident investigations have identified that operators are far more likely to come into contact with the cutters close to the fence due to workpiece 'kickback', rather than under the guard beside the workpiece. Kickback ejects the workpiece violently and unpredictably, leaving the cutters fully exposed where the workpiece used to be. There is therefore a considerable risk that the operators hand will make contact with the cutters when they become unbalanced and reach out for support, or when the following feeding hand passes directly over the now exposed cutters.
Information sheets & Circular saw poster
Approved Code of Practice and Guidance (ACOP)
DVD: Health and safety in the woodworking industry
BS EN’s for woodworking machines
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