Subscribe“Which garments provide the best protection against molten metal?” This question is frequently posed by Safety Managers, Purchasing officers and Union officials.
Because there are so many products on the market, it is not easy to decide which fabrics will meet best the worker's requirements.
The easiest course is, to rely on the appropriate industrial standard and select the cheapest product on offer. Unfortunately the easiest way is not always the best. European standards are, indeed, a very good starting point for evaluating the level of protection, but they do not cover all the aspects which should be taken into consideration, when purchasing protective clothing. The conditions on the shop floor are often different, to those imposed by the testing methods carried out under laboratory conditions.
Therefore, a degree of knowledge about the characteristics of the products on offer and the relevant standards is very important for people who have the responsibility of deciding which is the right personal protective equipment for their own particular plant.
Industrial sectors which pose the risk of molten metal splashes are one of the most hostile and dangerous working environments. Workers are not only exposed to a very high level of radiant and convective heat, but substantial splashes of molten metal and cryolite, and at times electric arcing. This has presented the textile industry with a real challenge.
"The conditions on the shop floor are often different, to those imposed by the testing methods carried out under laboratory conditions!"
As a result, it has been necessary to invent and develop solutions in order to ensure, that people working in this hazardous area of manufacturing should be able to carry out their tasks as safely and efficiently as possible.
Workers wearing garments made of Lenzing FRŽ
Protective clothing made with Lenzing FRŽ fiber include the following performance features:
- Shed molten metal and cryolite
- Resist exposure to flame without shrinkage
- Provide insulation against radiant and convective heat
- Protect against electric arcing
- Comfort- functionality
- Maintain appearance and strength
- Be acceptable in cost
To point 1: Shed molten metal and cryolite
Most severe dangers are impacts of molten metal splashes. Protective clothing needs to shed the molten substance quick enough, to avoid any burn injuries to the workers skin. Due to this quick shedding effect, the heat transfer through the garment is discontinued. Some materials have excellent metal shedding properties some are not suitable for protective clothing.
To point 2: Resist exposure to flame without shrinkage
Due to the hot metal splash impacts (Steel approx. 1600°C Aluminum/Cryolite 800-1200°C...) and the tremendous radiant heat, garments, which are not highly flame resistant will flame immediately. Flame resistance can be achieved by using inherently flame resistant fibers like for example Lenzing FRŽ (flame resistant cellulosic fiber) or treatments of wool or cotton.
This treatments provide, if the garment is new, the same flame resistance like inherently flame resistant fibers, but some endusers claimed, that the treatment can be laundered out or even evaporate by the tremendous high radiant heat in the plant. A treatment never offers permanent protection. Additionally it is very important, that the garment does not emit toxic fumes. Some treatments are based on halogens, brominates or contain antimonies, which are dangerous when inhaled.
Garment combination made of Lenzing FRŽ fiber
To point 3: Provide insulation against radiant and convective heat
This issue is often underestimated. Insulation is very important to protect against external heat sources. Garments need to protect against the heat from out side but also allow the body-heat to escape. The fabric respectively the garment weight is very decisive. The textile experts are speaking about the double edged sword.
A bulky and heavy garment temporarily provides good protection against radiant heat, but the wearer will soon collapse, because his body heat is trapped inside. This can lead to muscle cramps, dehydration, fatigue, heat stress and in the worst case result in a heat stroke.
To point 4: Protect against electric arcing
The metal industry is a very "energy hungry" industry. Much electric power is used to melt the metals, especially in aluminum smelting plants. Those people which handle the power for the production are exposed to this additional risk. The risk at an electric arc incident is not so much the high voltage, as the very high temperature of a brief arc and the small molten metal splashes it projects from the electrodes. Insulation by the garment is an important factor also in this case.
Protect against electric arcing
This pictures compare two different fabrics after an electric arc exposure with 8 kA according to the NFPA 70E standard:
- A is a Lenzing FRŽ fabric after the arc flash
- B is a Vinal fabric after the arc flash
- C is the Vinal fabric before the arc flash.
To point 5: Comfort- functionality
This is a very complex topic. If the garment is not comfortable the worker will not accept and wear it. Protective Clothing helps only, if correctly worn!
Lenzing FRŽ blended garments provide the best comfort to the end users.
To point 6: Maintain appearance and strength;
Mechanical properties like tear strength, pilling and abrasion, as well as colour fastness are important to assess the lifetime of a garment.
To point 7: Be acceptable in cost
Highly sophisticated fabrics are not cheap. The garment's durability must be taken into consideration when judging the cost of protective clothing. To save money on protective clothing is to risk the life of the workers.
Historically, the first garments designed to give protection against molten-metal splash were made from very heavy wool fabrics. As the level of protection was low, the material came to be treated with non flammable products such as Zirpro. As the protection level was increased, there was increasing incompatibility between the protective agent and the fabric.
At the same time, the non- flammable treatment provoked allergies due to the presence of chemicals such as Circonio salts. Although the level of protection improved by increasing the weight of the fabric and the introduction of new treatments, garments still needed to be used selectively if they were to resist the impact of some specific molten metals. As a result, it was widely accepted throughout the latter part of the 1980's and into the 1990's that FR-treated fabrics had a number of limitations.
At the end of the 1990's, a completely new range of fabrics was introduced to the marketplace. These materials were blends of Lenzing FRŽ (inherently flameresistant cellulose-type fibre) and wool. Such fabrics offered a new dimension of safety and comfort to the end- user. As a result, they are well on the way to being the unmatched leader in fabrics used in the tailoring of protective clothing for workers exposed to molten aluminium and cryolite splash.
"Lenzing FRŽ is inherently flame resistant!"
Fabrics made with Lenzing FRŽ and natural fiber fulfil Norm EN 531 with the following results:
- ISO/EN 15025 - Limited flame spread Pass (Index 3)
- EN 366 - Radiant heat Level 2
- EN 367 - Convective heat Level 1
- EN 373 - Molten metal splash
- Aluminium min. Level D-3
- Iron min. Level E-3
The Lenzing FRŽ blend has maintained its position as the benchmark standard for protective fabrics across all smelter environments. The multi-functionality of garments offers molten metal operatives a complete solution 'system' across the smelter site from the pot-room through to re-melt, casting, rodding, electrical and maintenance operations. It is now endorsed by some of the largest smelter corporations in the world as the fabric of choice for molten aluminium and cryolite protection.
Currently products made of Lenzing FRŽ are widely employed as the protective fabric of choice throughout Australasia, Europe, South America and the United States. Indeed, wherever the health and safety of hot metal operatives is regarded as paramount, one can almost guarantee that Lenzing FRŽ is already in situ or at least involved in ongoing trials for impending implementations.
Case History
In October 2002 a terrifying accident has shocked all workers in a smelting plant. In the subsequent investigation, it was calculated , that the operator involved in this mishap had supported more than 30 kg of molten Aluminum without severe damage as a result of wearing garments made from Lenzing FRŽ.
