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Arc flash protection | A whitepaper on clothing & garment selection

Author : Hamilton Smith, Technical Sales Manager, ProGarm

01 September 2020

An arc flash is the light and heat produced as part of an arc fault; a type of electrical explosion or discharge that results from a low impedance connection through air to ground or another voltage phase in an electrical system.

In laymans’ terms:

An arc flash occurs when electrical current jumps across an air gap between conductors, like when lightning jumps down to earth.

That large instantaneous discharge of electrical current causes an explosion:

– Extremely high levels of energy, heat and light are released in fractions of seconds

– Temperatures can reach up to 35,000ºF (19,000ºC) = 4 times the temperature of the Sun’s surface!

– A blast and pressure wave that can damage eardrums and even strip away garments

Where and when does an arc flash occur?

Where?

Industrial electrical environments – Factories, manufacturing plants, electrical maintenance even including areas such as electric vehicle maintenance and manufacture

Power generation -Traditional environments but also including renewables such as wind turbine maintenance

Utilities – Anyone breaking ground in electrical, gas and water, even operatives installing street lights

Rail sector – Electrification and maintenance

Petrochemicals – Protecting plant workers and even tanker drivers in the same way as for arc flash against flash fire

When?

Whilst undertaking installation, maintenance or repairs, but also when breaking ground, undertaking excavations and construction

Why does an arc flash occur?

- Tools or equipment inadvertently touch live conductors or are dropped
- Faults or mistakes in isolating equipment
- Equipment failure due to faulty parts, poor installation, or even normal wear + tear
- Dust, corrosion or other impurities on conductor surfaces
- Cable strikes when breaking ground 8 to 10 cable strikes are reported daily in the UK!

Arc flash vs. operative... only one winner!

- Skin burns right to 3 rd degree from direct heat exposure
- Damage to eyesight caused by heat and the high intensity flash which includes UV light
- Hearing loss and physical damage as the blast can greatly exceed the sound of a jet engine
- Significant injury risks from flying debris such as equipment, shrapnel wounds and molten metal
- Loss of memory or permanent impairment of brain function from concussion
- Burns from hot liquids in oil cooled or insulated equipment
- Other physical injuries from being blown off ladders, into walls etc

It’s no exaggeration when we say the implications and injuries can be life threatening, they’re certainly life changing.

Employee protection - what can be done?

Employers have a duty to protect their employees against injury and other hazards.

There is a hierarchy of steps to safeguard workers:

1. Reduce the exposure of operatives to risk
2. Define and enforce safe working practices to reduce risk – they can undertake an AF study
3. Provide appropriate level sot PPE – AF assessments or studies can help to predict potential exposure and suggest the level of protection.

PPE is designed to reduce the risk of life changing or life threatening 2nd or 3rd degree burns. Arc flash clothing and PPE is the last line of defence when risks cannot be totally eliminated.

Arc flash protection standards


IEC 61482 2 : 2018 Protective Clothing Against the Thermal Hazards of Electric Arc

Arc flash testing information – there are two test methods:

BS EN IEC 61482-1 1:2019

Method 1: Determination of the arc rating (ELIM, ATPV and/or EBT) of clothing materials and of protective clothing using an open arc (Open Arc Test).

- ATPV = Arc Thermal Performance Value:

the value of incident energy at which the heat transfer through the test specimen is enough to reach the Stoll criteria with 50% probability of 2nd degree burn e.g. if a product that achieves 8cal/cm² ATPV, is hit with 8cal arc exposure then there is 50% probability of 2nd degree burns.

- EBT = Breakopen Threshold Energy:

the value of incident energy at which breakopen occurs with 50% probability of 2nd degree burn e.g. a product that achieves 8cal/cm² EBT, if hit with 8cal arc exposure then there is 50% probability of 2nd degree burn and with breakopen of material.

- ELIM = Incident Energy Limit:

a numerical value of incident energy attributed to a product, below which there is no data point with the amount of heat transmitted through the product reaching the Stoll criteria or with the product exhibiting breakopen e.g. a product that achieves 8cal/cm² ELIM, if hit with 8cal arc exposure then there is 0% probability of 2nd degree burn.

IEC 61482 2 : 2018 Protective Clothing Against the Thermal Hazards of Electric Arc

Arc flash testing information – there are two test methods:

BS EN 61482-1 2:2014

Method 2: Determination of arc protection class of material and clothing by using a constrained and directed arc (Box Test)

APC 1 (Class 1):

– test current 4kA (+/-5%)
– voltage 400 volts a.c. (+/-5%)
– arc duration 500 ms (+/-5%)
– frequency either 50hz (+/- 0.1hz) or 60hz (+/- 0.12hz)

APC 2 (Class 2):

– test current 7kA (+/-5%)
– voltage 400 volts a.c. (+/-5%)
– arc duration 500 ms (+/-5%)
– frequency either 50hz (+/ 0.1hz) or 60hz (+/ 0.12hz)

Fibres, fabrics & creating protective garments

Treated vs Inherent

- At ProGARM we believe fundamentally that inherent FR fabrics offer the best solution

- Traditionally treated fabrics have been stiff, uncomfortable, lacked breathability and even smelly!

- Protection from treatments reduces every time a garment is washed

- Inherent means that characteristically the fibre will not burn – Inherent fibres create inherent yarns which are knitted or woven into inherent fabrics instant extinguishing

Our fabrics are called VXS+

Clothing systems

Examples of garments that are often combined into a PPE system

Protection in layers where 1 + 1 = 3

Make sure they are the right layers though

- We’ve developed a total range of garments from underwear and thermal base layers to 47cal waterproofs

- Many H&S Managers and operatives are not aware that wearing the wrong fabrics, even under AF protective garments, can compromise the AF garments and result in injury

What makes a great garment?

Let’s take a look at some of the features that protect and save lives.

Arc flash garment features to be aware of:

Take a look at the garment design features that show the attention to detail.

Triple stitched seams
Inherent fabric & instant extinguishing
FR threads
ThermSAFE components tested to continue to function after an incident
Wrist tabs and neck fastening
Reflective tape
SafetyICON marking
Internal labelling inc batch numbers for traceability
Stretch panels
Napoleon pockets for harnesses
Garments available from S to 4XL
Women’s garments

Let's sum up

Education is one of our core missions – we’re here to help.

ProGARM’s Mission

Educate and inform to save lives
Constantly develop and innovate
Deliver an exceptional customer experience
Never compromise. Lives depend on it

We’re here to help you find the right solution for your operatives who are at risk of an electric arc to make sure they come home safely.

For more information, visit: https://www.powerandcables.com/arc-flash-protection-a-whitepaper-on-clothing-garment-selection/


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