The type of work and the risks to which a person is exposed during their working hours makes it necessary to develop suitable Personal Protective Equipment (PPE). PPE must offer a variety of benefits to assure the correct protection and good health conditions for those using it.
One of the most important types of PPE is footwear. This must protect the foot from at least four hazardous situations: compression, impact, punctures and chemical products. However, there are also what we refer to as special risks, and these include electrical, mechanical and cutting with chainsaws.
According to the Spanish National Institute for Occupational Safety and Health (INSHT) the three types of footwear differentiated in an initial basic classification are:
- Safety footwear – footwear that includes elements to protect the user from risks that can cause accidents, equipped with a safety part to protect the toes. Safety footwear is designed to offer protection against impact when it is tested with an energy level of at least 200 J and against compression when it is tested with a load of at least 15 kN.
- Protective footwear – footwear with elements to protect the user from risks that can produce accidents, equipped with a special part to protect the toes. Protective footwear is designed to offer protection against impact when it is tested with an energy level of at least 100 J and against compression when it is tested with a load of at least 10 kN.
- Occupational footwear – footwear that includes elements to protect the user from risks that can result in accidents. It does not guarantee protection against impact and compression in the front part of the foot.
Depending on the manufacturing material, there are two categories:
- Category I – footwear produced with leather and other materials, excluded footwear made completely with rubber or polymeric materials
- Category II – footwear manufactured entirely with rubber (for instance, completely vulcanised) or totally polymeric (for example, completely moulded).
Any of the three types, within these two possible categories, deliver a set of benefits that allow them to offer protection against several risks.
Regulations for footwear
PPE and footwear must meet the requirements under the specific standards according to the type of work in which they are going to be used. For footwear, these include:
- Standard UNE-EN ISO 20345:2012. Personal protective equipment – Safety footwear
- Standard UNE-EN ISO 20346:2014. Personal protective equipment – Protective footwear
- Standard UNE-EN ISO 20347:2013. Personal protective equipment – Occupational footwear
- Standard UNE-EN ISO 17249:2014. Safety footwear with resistance to chainsaw cutting
- Standard UNE-EN 13832-1:2007. Footwear protecting against chemicals – Part 1: Terminology and test methods
- Standard UNE-EN 13832-2:2007. Footwear protecting against chemicals – Part 2: Requirements for footwear resistant to chemicals under laboratory conditions
- Standard UNE-EN 13832-3:2007. Footwear protecting against chemicals – Part 3: Requirements for footwear highly resistant to chemicals under laboratory conditions
- Standard UNE-EN 15090:2007. Footwear for firefighters
- Standard UNE-EN 50321:2000. Electrically insulating footwear for working on low voltage installations
- Standard UNE-EN ISO 13634:2012. Protective footwear for motorcycle riders – Requirements and test methods
- Standard UNE-EN ISO 20349:2011. Personal protective equipment – Footwear protecting against thermal risks and molten metal splashes as found in foundries and welding – Requirements and test method
Moreover, most parts of the methodology to obtain the required values are shown in the Standard UNE-EN ISO 20344:2012 ‘Personal protective equipment – Test methods for footwear’, that explains the procedures to test the complete footwear as well as the individual components. In this article, some of the methods for whole footwear proposed in this standard will be detailed.
UNE EN ISO 20344:2012
The standard UNE-EN ISO 20344:2012 lists until 17 test methods for complete footwear. These tests are usually carried out in the laboratory to control the quality and detect errors in the production systems.
Specific ergonomic features
The specific ergonomic features for footwear must be verified through using tests over three testers with different sizes. Testers must simulate typical tasks carried out during general use, such as walking, climbing and descending steps, and kneeling/ crouching down with a knee on the ground, to complete a questionnaire later.
Determination of upper/outsole and sole interlayer bond strength
This test measures the strength required to separate the upper and outsole, as well as the layers of the sole, or to cause a tear on the upper or on the sole.
The aim is to assess the resistance of the pasting in the area located near the edge of the bond. In Figure 1, a test sample is shown during the test.
Figure 1: Test for the determination of the upper/outsole bond strength
Determination of internal toecap length
This determines the internal length of the toecap, that is, its depth or usable space.
Determination of impact resistance
A piece of steel within the equipment shown in Figure 2 is dropped on the front part of the shoe. The drop height is the height required to obtain the needed impact energy, calculated as potential energy. The assessment is carried out through the free span inside the toecap at the moment of the impact, measured with a cylinder of modelling clay. The deformation is measured (final height) using a micrometre.
Figure 2: Equipment to determine the impact resistance
Determination of compression resistance
The front part of the footwear is compressed between the plates of a dynamometer (see Figure 3). To evaluate the compression resistance, the free span inside the toecap is measured when the dynamometer reaches the required compression strength, through a cylinder of modelling clay located in a similar way to the impact test.
Figure 3: Equipment to determine the compression resistance
Behaviour of toecaps and inserts (thermal and chemical)
In the case of metallic toecaps and inserts, this test measures the corrosion resistance, testing them under the action of sodium chloride. In the case of non-metallic toecaps and inserts, the impact resistance of the toecaps is measured after thermal and chemical ageing treatments.
Determination of the dimensional conformity of inserts and the penetration resistance of the sole
The location of the insert is checked in relation to the protective toecap and the last, as well as the presence of holes in the insert.
Figure 4: Tooling for the perforation test
In the case of footwear that includes metallic inserts, the resistance to penetration is defined as the maximum strength that must be applied to perforate the sole with a normalised punch (see Figure 4), pushing perpendicularly to the footstep surface.
In the case of footwear that includes non-metallic inserts, the resistance to penetration is defined as the fact that the perforation happens, or not, with the normalised punch and a strength of 1100 N, pushing perpendicularly to the footstep surface.
Determination of the flex resistance of penetration-resistant inserts
The behaviour under flexion of the anti-puncture insert is determined visually, after 106 flexion cycles at a frequency of 16 cycles/s. The equipment is shown on Figure 5.
Figure 5: Inserts flexometer
Determination of electrical resistance
The electrical resistance of conductive footwear is measured after conditioning in a dry atmosphere. The electrical resistance for antistatic footwear is measured both after conditioning in a dry atmosphere and a wet atmosphere.
The electrical resistance is determined by transferring a direct current at a voltage defined through the shoe or boot.
Determination of footwear slip resistance
The simple test is located on the test surface (see Figure 6), with a specific vertical load. The surface moves and the horizontal friction strength is measured, calculating the dynamic coefficient of friction (CoF), dividing the value of the friction strength by the normal force.
Figure 6: Equipment to determine the slip resistance
Determination of insulation against heat
This test determines the variation of the temperature inside the footwear after a temperature increase within a sand bath, as shown in Figure 7.
Figure 7: Equipment to determine the resistance against heat
Determination of insulation against cold
This test determines the variation of the temperature inside the shoe after leaving it for 30 minutes in a refrigerator at a temperature of -17ºC, as shown in Figure 8.
Figure 8: Equipment to determine the resistance against cold
Determination of energy absorption of the seat region
This test determines the energy absorbed by the heel area when a force of 5000 N is applied with the rear part of a last. For that, it uses a dynamometer, as shown in Figure 9.
Figure 9: Test to determine the energy absorption of the seat region
Determination of the resistance to water for whole footwear
The objective of this method is to offer a way to assess the resistance to water for footwear. The footwear is secured in a flexion machine with water, such as the one shown in Figure 10, until a height defined over the line of the bond upper-outsole. To conduct this test, the footwear is flexed at a constant speed and the penetration of water is reviewed at intervals.
Figure 10: Equipment to determine the resistance to water