Earthing portable concrete vibrator

[Driftn]

Hi All,

I am working as a lead electrical field engineer on an Aluminum Smelter in Bahrain. I am an American using the British Standards for the first time, a lot to learn. The question: the site safety department is requesting the subcontractors to earth (drive earthing rods) portable gas driven concrete vibrators. The one vibrator I looked at is rated 42 Volts, .55 Amps, 200 Hz. I have researched several sites looking for vendor manuals on gas driven concrete vibrators and have not found any site discussing earthing the portable vibrators.

I would like some feed back so I can argue with safety that earthing is not required or feed back to show the subcontractors earthing is required.

Thanks,
Kurt

 

[hivolt]

All the portable electrical equipment are earthed to prevent paiful shock and/or fatal shock to the person handling it.Also even if someone is normaly not holding it with hands it needs touching sometimes .If the equipment is not earthed
whoever touches it will get electricuted.Hence it has to be earthed for SAFETY REASONS.Just earthing is not effective if you dont have appropriate earth leakage relays of 30 milli Amp rating at the upsreame to cut he power OFF when there is earth fault. Even if it is driven by Air,then also Earthing is required to drain off the possibly accumulated static electric charges,which can reach dangerously high enough level to cause/create shocks or sparks& consequent fires.However for the static charge to get drained off, its not neccessary to go for solid earthing methods,an earth resistance of the order of few mega ohms is OK.The bottom line is there is nothing wrong in earthing the vibrator ,may be the chances are you will be saving someone from a SHOCK. So go ahead and START EARTHING the vibrator.

 

[Skogsgurra]

Driftn,

42 V AC is PELV (Protective Extra Low Voltage) and there is most certainly a reason why the manufacturer has chosen such a low voltage. As you probably already guessed, the reason is that you shall be able to run without any earthing at all.

I beg your pardon hivolt, but I think that you got carried away by the safety issue. Your advice would mean a lot of unnecessary inconveniance to Driftn - and no better safety at all. Probably a decrease in safety because there would be many "trip wires" on the site if you were to ground every rod.

 

[Ahr35181]

In the UK:-

42V AC is ELV (i.e less than 50V a.c)

The vibrators could be SELV (Seperated (FROM EARTH) Extra Low Voltage) which is class III, in which case it must not be connected to earth.

Or they could be PELV (Protective Extra Low Voltage)which is NOT electrically seperated from earth, but which otherwise satisfies all the requirements for SELV. PELV requires protection against indirect contact, therefore the use of an earth rod may be advisable.

My guess is the units are class III, the symbol for class III equipment is shown in the IEE code of practice for In-Service Inspection and Testing of Electrical Equipment.

If they are class III, they must not be connected to earth.

Alan

 

[Driftn]

Thanks to everyone,

I found the IEC 60745-1 standard on Hand Held Motor Operated Electric Tools Safety and per the information in this IEC standard and the information I have found on the gas driven vibrator it meets the class III requirements.

Thanks,
Driftn