How much does braking cost?
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 I turn the machine off at the isolator, why doesn’t the brake work?
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.
Should there be a secondary power supply for d.c. braking if the E-stops in a workshop turns off the power to all machines?
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.
I use a pull over cross-cut saw which has a manual brake fitted. Do I still need to fit electric braking?
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.
What if my cross-cut has no manual brake?
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.
I use a variety of different cutting blades on my cross-cut saw. How does this affect braking?
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’.
Why do Planer/Thicknessers have to be braked? The cutters are all enclosed within the machine.
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.
Is there any requirement to have woodworking machinery electrically tested to ensure that it is in a safe electrical condition?
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:
- Regulation 4(2) is concerned with the need for maintenance to be done to ensure the safety of the system…
- The obligation to maintain arises only if danger would otherwise result. The quality and frequency of maintenance should be sufficient to prevent danger, so far as is reasonably practicable.
- Regular inspection of equipment is an essential part of any preventative maintenance programme. Practical experience of use may indicate a change in how often preventative maintenance needs to be carried out. This is a matter of judgement of the duty holder who should get all the information he needs before making this decision, including reference to the equipment manufacturer's guidance.
- Records of maintenance include test results and these should be kept throughout the working life of the electrical system. This is because it will allow the condition of the equipment and the effectiveness of the maintenance policies to be monitored. Without effective monitoring, dutyholders cannot be certain that the requirement for maintenance have been complied with.
The following definitions are given in HSR25:
- means an electrical system in which all the electrical equipment is, or may be, electrically connected to a common source of electrical energy, and includes such source and such equipment
- "electrical equipment"
- includes anything used, intended to be used or installed for use, to generate, provide, transmit, transform, rectify, convert, conduct, distribute, control, store, measurement or use of electrical energy.
Further advice on inspection and testing of fixed installations can be found in:
- BS 7671:2008 Requirements for electrical installations;
- IEE Wiring Regulations Seventeenth Edition;
- BS EN 60204-1:2006 Safety of machinery. Electrical equipment of machines. General requirements;
- Additional references are given in Appendix 2 of The Electricity at Work Regulations 1989 (HSR25).
Is a manufacturer required to perform an EN 60204 electrical installation test if a new machine that has been tested after manufacture is then disassembled for transport and re-assembled on site?
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 planing and moulding machines
Should Four-sided Planer Moulders be braked?
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:
- On older four-sided planer moulders the spindle stopping time can be as high as five minutes.
- Most accidents could have been prevented if the cutters had come to rest before operators approached them.
- Out of 125 accidents investigated access to the cutters with the machinery running was only necessary in 17 cases.
- About half of all accidents were caused by people approaching the cutters.
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 new machines interlocks are fitted to enclosure access doors that cut power, stop the feed and apply brakes. What is the standard for older machines?
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).
Considering the high number of accidents that occur during adjusting and setting four sided-planer moulders, how should setting be done safely, particularly on an old machine?
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:
- Hood/extraction enclosures around the cutter blocks, particularly the vertical and horizontal top cutter blocks, which also provides effective guarding.
- A bridge type guard, similar to that used on a hand fed surface planer that covers the bottom horizontal heads.
- Guards are only removed or opened when the machine is stopped and being cleaned/maintained or a cutter block is being fitted to the spindle during a tool changing operation.
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:
- Only adequately trained and experienced employees should be authorised to carry out setting and adjustment and only the setter should be allowed in the working area of the machine during setting operations.
- Access to cutters must be prevented during setting.
- Suitable eye, ear and foot protection must be worn and RPE (Respiratory protective equipment) if necessary. There should be no loose clothing that could cause entanglement.
- The correct tools and equipment must be used and be located in a safe area.
- The immediate floor area must be clean and kept clear of all obstructions and tripping hazards.
- Fitting cutters
- Many injuries occur when cutter blocks are being handled, either because of the sharp cutters or the weight of the block.
- Protective gloves should be worn, suitable for handling sharp and possibly oily cutter blocks. Gloves should provide a good grip and be able to prevent cuts and abrasions.
- Cutter blocks can weigh up to 30 kg and may need to be fitted at arms length so the risk of injuries can be high. Cutters should therefore be moved on a trolley and a mechanical device to help them being lifted on and off the spindle may be needed.
Medium Density Fibreboard (MDF)
What is MDF?
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.
What are the dangers of working with MDF compared with softwoods, hardwoods or other panel products?
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.
What is formaldehyde and where does it come from?
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.
How much formaldehyde is released by MDF board?
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.
How are MDF boards labelled?
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.
Is MDF banned in other countries and, if so, why not in the UK?
HSE is not aware of any countries in the world where MDF is banned.
What precautions should be taken when working with MDF?
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:
- Formaldehyde - 2.5 mg/m3 or 2 ppm for both the long-term exposure limit and the short-term exposure limit
- The WEL for hardwood dust is 3mg/m3 (based on an 8-hour time-weighted average). The WEL for softwood dust is 5mg/m3 (based on an 8-hour time-weighted average). For mixtures of hardwood and softwood dusts the WEL for hardwood dust of 3mg/m3 applies to all wood dusts present in that mixture. There is no short-term WEL
To control exposures, employers should follow the ‘hierarchy of control’ set out in the COSHH Regulations. This means:
- First, try to reduce risks at source where possible by using a lower risk alternative, where one exists. An example of this could be to use a ‘no added formaldehyde’ MDF board or low-emission MDF board if practicable to do so.
- There should be an effective dust extraction system in use whenever MDF is machined or sanded. This is often termed local exhaust ventilation (LEV).
- Vacuum equipment that meets at least the dust class M (medium hazard) classification should be used to clean up MDF dust, or use a hose connected to the LEV system. Airlines and brushes should not be used as these produce clouds of fine dust that is easily breathed in.
- Respiratory protective equipment (RPE) may also be needed but this will generally be the last line of protection.
If I do need to use respiratory protective equipment (RPE), what should I use – is a dust mask sufficient?
RPE should not be used as the only means of control as it should complement other control measures such as a dust extraction system. General information on RPE is available at "http://www.hse.gov.uk/pubns/books/hsg53.htm" www.hse.gov.uk/pubns/books/hsg53.htm
When you need to use RPE to provide protection against inhalation of wood dust, you should ensure that the RPE is adequate and suitable (for more information see http://www.hse.gov.uk/pubns/wis14.pdf ).
For RPE to be adequate you must select the right mask/respirator and filter. A face filtering piece (FFP) with an assigned protection factor of at least 20 e.g. FFP3 or a half-mask with a P3 particle filter can be used to protect against exposure to wood dust.
- Do not use nuisance dust masks, FFP1 or FFP2 as they do not provide sufficient protection. If organic vapours are also present eg formaldehyde, then a half-mask with both a P3 particle filter and an appropriate filter for the organic substance could be used.
- For RPE to be suitable it must fit the wearer and be appropriate for the task and environment. For tight-fitting masks like a dust mask you must ensure that the mask fits the worker by undertaking ‘face fit’ testing (for further details see Guidance on respiratory protective equipment (RPE) fit testing).
- Workers wearing tight-fitting masks must be clean-shaven as stubble prevents the mask sealing properly against the face. The mask worn should be compatible with any other protective equipment worn e.g. safety glasses, hearing protection.
Any RPE should be used correctly, and filters changed regularly, in accordance with the manufacturers instructions. Respirators must also be stored correctly and, for non-disposable RPE like half-masks, properly maintained by a competent person.