DGUV Information 209-090e - Activities relating to Magnesium (DGUV Information 2...

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Abschnitt 3, 3 Personal protective equipment/work clothes
Abschnitt 3
Activities relating to Magnesium (DGUV Information 209-090)
Titel: Activities relating to Magnesium (DGUV Information 209-090)
Normgeber: Bund
Amtliche Abkürzung: DGUV Information 209-090
Gliederungs-Nr.: [keine Angabe]
Normtyp: Satzung

Abschnitt 3 – 3 Personal protective equipment/work clothes

The choice of personal protective equipment depends on the respective activities and the operational conditions. A distinction is essentially made between the area of melting/casting and the area of machining of magnesium workpieces.

There is a risk that magnesium dust adhering to clothing can easily ignite. Therefore, protective clothing worn during machining of magnesium must never be used in areas with molten magnesium. A change of protective clothing is therefore necessary.

If the clothing soiled with magnesium dust has to be cleaned, it is essential to observe the washing instructions given by the clothing manufacturer.

Personal Protective Equipment (PPE), machining area

The main hazard during machining, especially during dry grinding, is the accumulation of magnesium dusts and chips on protective work clothes. These particles adhering to the protective work clothes are highly flammable. For this reason, a clothing fire containing magnesium can spread very quickly and extremely violently.

Therefore, suitable protective clothing with a smooth surface without pockets (e. g. rubber or leather apron) must be worn. The quantity of magnesium dust adhering to the work clothes can thus be minimized.

In general, clothing should be cleaned regularly to remove adhering magnesium residues.

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Under no circumstances may clothing be blown off with compressed air or worn during activities involving fire hazards (welding)!

Personal Protective Equipment (PPE), melting/casting area

In the melting/casting area, the following personal protective equipment is worn, depending on the risk assessment:

  • foundry clothing (protective clothing and underwear according to DIN EN ISO 11612)

  • foundry helmet

  • foot protection

  • gloves

and, according to the risk assessment, also

  • safety goggles with side protection

  • ear protection

  • respiratory protection

In areas with direct contact with molten metal (e. g. skimming on the furnace platform, cleaning of pumps, manual casting, ...)

  • foundry clothing (protective clothing, underwear and aluminised foundry coat for direct contact with molten metal according to DIN EN ISO 11612),

  • head and face protection (e. g. foundry helmet with visor, neck guard, hood),

  • foot protection, possibly gaiters,

  • foundry gloves

have to be worn in addition.

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Figure 28
Protective oven suit

Foundry clothing

The selection of protective clothing against heat and flames when handling molten metals is carried out in accordance with DIN EN ISO 11612. In addition, DIN EN ISO 9185 (formerly DIN EN 373) assesses the material resistance to liquid metal splashes and DIN EN ISO 15025 (formerly DIN EN 532 ) assesses the fire behavior of protective clothing.

When handling molten magnesium (e. g. skimming, molten metal treatment, furnace cleaning, etc.), particular attention must be paid to the drip off properties of the molten metal and the low flammability of the fabric. A textile material has good drip off properties, if molten magnesium does not remain adhered.

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Figure 29
Burnt unsuitable protective clothing

The above mentioned requirements are divided into classes in DIN EN ISO 11612:

  • A Flaming of materials and seams (DIN EN ISO 15025)

  • B Protection against convective heat (DIN EN ISO 9151)

  • C Protection against radiant heat (ISO 6942 method B)

  • D Protection against molten aluminum

    (DIN EN ISO 9185)

  • E Protection against molten iron (DIN EN ISO 9185)

  • F Contact heat (ISO 12127-1)

For foundries, classes D and E are of particular importance. For protection against molten magnesium, it is recommended to wear clothing of class D3, based on the protection against molten aluminium.

The manufacturer must provide appropriate proof of the suitability of the clothing. As a rule, this is done by means of pouring tests in accordance with DIN EN ISO 9185 with the magnesium alloy used.

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Figure 30
Pouring tests

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Figure 31
Pouring tests

The performance of the pouring tests is also described in DGUV Information 212-013 "Hitzeschutzkleidung" ("Heat protection clothing") in Section 4.3. It also contains further information on heat protection clothing.

In contrast to the aluminized foundry coat, the underwear/work clothes may have pockets. However, these must have flaps (e. g. pocket flaps) that are at least 20 mm wider than the pocket opening (10 mm on each side). This prevents ingress of molten magnesium and dust (roof tile principle).

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Company logos and reflective strips, the names of employees or companies that are subsequently attached can lead to a reduction of the protective function of the protective clothing.

If a subsequent attachment is necessary, it should only be done in consultation with the manufacturer of the personal protective equipment. This ensures that the emblems are attached at an uncritical position (roof tile principle still ensured).

The material used for the foundry coat is a flame-resistant fabric metallised with aluminium ("silver clothing"). The metallization protects against the radiant heat of the molten metal during a metal fire.

Objects such as lighters, smartphones and torches must not be carried in trouser or jacket pockets near the molten mass. There is a risk of explosive molten metal ejection if the objects fall into the molten metal.

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Figure 32
Molten metal ejection in case of a lithium ion accumulator (smartphone, torch)

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Figure 33
Helmet and face shield; here: hood with air supply

Foundry helmet and face shield

Requirements for industrial helmets are defined in DIN EN 397. In general, thermoset helmets with textile fibre reinforcement (unpainted or painted) as well as thermoset helmets without textile fibre reinforcement based on polycarbonate are used in foundry areas in case of hazards caused by splashes of molten metal and/or by use at very high temperatures above 150 C).

The face shield shall be designed to provide adequate protection against metal splashes, flames and, if necessary, optical radiation (UV/IR radiation portion) (e. g. gold-plated visor).

Foot protection

In a foundry environment, foot protection includes safety shoes and gaiters.

To ensure that the shoes offer sufficient protection against penetration of metal splashes, they must be at least ankle high. In addition, they should be designed in such a way that they can be taken off quickly (quick release fastener). Furthermore, at least protection class S2 must be ensured. The requirements for the material correspond to those for protective clothing (low flammability, drip off properties).

Foundry gloves

If there is a risk of hand burns, suitable protective gloves have to be worn that insulate against the effects of heat. In areas with a risk of ejection of molten metal, gloves must be worn which consist of the same aluminized material as the foundry coat, for example.

Requirements are dealt with in DIN EN 407 "Protective gloves against thermal risks (heat and/or fire)".

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Figure 34
Example of the labeling of heat protection gloves according to EN 407

Underwear

Special attention should also be paid to the fabric of the underwear. Synthetic fibres can melt quickly on the skin and, in the worst case, have to be surgically removed. In the risk assessment, it must be determined and specified for each individual case which underwear should be worn.

It is generally recommended to choose underwear that does not contain any synthetic fibers.

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Clothing with finished fabrics releases more unpleasant gases when exposed to heat than clothing with inherently flame-retardant fabrics. For finished fabrics, attention must also be paid to the maximum number of washing cycles for which the certified protection is guaranteed.

Respiratory protection

The selection and use of respiratory protective devices is described in detail in DGUV Rule 112-190 "Benutzung von Atemschutzgeräten".

In case of high dust exposure, for example during the regular drossing process, the use of a separately ventilated airstream helmet has proven its worth.

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Figure 35
Helmet and face shield; here hood with air supply

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Respiratory protection for Mg work should not be used for other activities, for example when grinding steel. There is a risk that Mg particles in the filter suddenly ignite due to sparks from other activities.