Testing gloves against high voltages
Tests can be carried out on gloves to assess protection against high voltages.
The effects of electricity flowing through the human body vary from a tingling sensation at a current of 1-2mA, through pain at 5-6mA to muscle spasms above 20mA. Clearly we are all different and these values are only approximate but the dangers are clear. As with all hazardous tasks, the hierarchy of risk reduction always starts with trying to do the work in a different way that either removes or reduces the hazard. For instance, the risk of shock can be removed if it is possible to work on the equipment with the supply disconnected, locked off and earthed. However, the final line of defence is to use items of personal protective equipment (PPE), such as protective gloves, which have been tested and approved as providing an acceptable level of protection against contact with a high voltage.
Glove testing in Europe
The European standard covering such gloves is EN 60903 – 'Live working. Gloves of insulating material'. It includes a range of tests, some of which are optional and only carried out if a specific property is to be claimed. The mandatory test assessments include checks on dimensions, finish, marking and packaging, plus tests on basic mechanical performance, dielectric properties, ageing treatments and thermal tests.
The basic mechanical performance tests cover tensile strength and elongation at break and puncture resistance. Several performance levels are available for the dielectric or electrical insulation tests (see box 1). The thermal requirements consist of a flame retardancy test on the glove fingers and a cold crack test carried out after exposure to a minus 25ºC environment. Optional tests for gloves with special properties, together with their associated marking codes, are listed in box 2.
|Box 1: Electrical insulation tests|
|Class||Maximum use voltage||Colour code*||AC proof
|00||500V ac / 750V dc||Beige||2.5||5|
|0||1,000V ac / 1,500V dc||Red||5||10|
|1||7,500V ac / 11,250V dc||White||10||20|
|2||17,000V ac / 25,500V dc||Yellow||20||30|
|3||26,500V ac / 39,750V dc||Green||30||40|
|4||36,000V ac / 54,000V dc||Orange||40||50|
|*Optional colour code for marking symbols|
|Box 2: Optional tests on gloves with special properties|
|Special property||Marking code|
|Acid, oil and ozone resistance||R|
|Extreme low temperature||C|
|Increased mechanical properties (blade cut, tear and puncture)||Mechanical pictogram|
SATRA test equipment
The photograph shows the high voltage test apparatus which is used in SATRA’s labs for the EN 60903 electrical testing. Most European tests for insulation resistance assess performance in what is considered to be a worst-case situation – that is, when the sample is wet, as moisture will usually aid the flow of current. This means the test protocol often includes a pre-treatment procedure to maximise the moisture content of the product. This is either achieved by storage in an environment with a defined high humidity, or (as is the case in EN 60903) by immersion in water.
High voltage tests on various products such as gloves typically include insulation resistance measurement and dielectric strength (electrical flashover). Thus a test may apply 5kV to the sample for three minutes, during which time the leakage current is recorded – this is usually called the proof test voltage. The voltage is then increased to a level referred to as the ‘withstand voltage’ and the product is assessed for resistance to electrical puncture (see box 1).
SATRA can also test sleeves to EN 60984.
Further information on SATRA's PPE certification and testing services is available at www.satra.com/ppe
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