Tank Earthing

[Leinster]

In the past we have always earthed storage tanks into a "earthing pit" right next to the tank... We have just come across a consultant who is insisting that all earthing should be done outside of the bund wall as when it rains the whole bund area will become charged.

What are your opinions on this?

 

[adamuk]

I think your 'consultant' should do gen up on some basic electics first.

Any earth will be held at 'ground' potential which is 0 Volts so any charge developing anywhere near a conductor that was earthed would immediately cause a current to flow and the voltage to drop.

Vessels and tanks are earthed as a static charge can form when nonconducting fluids flow these (a bit like rubbing a balloon on your sweater as a child). The earthing prevents the static charge from getting high enough to cause a spark (and thus catastrophe in chemical plant, potentially)

Typically here in the UK the earth bonding checks should indicate a resistance of 10 ohms or less to earth.

HTH

Adam.

Adam Potter MEng CEng MIMechE

http://www.ax-ea.co.uk

 

[Duwe6]

10 ohms = marginally acceptable
<2 ohms = good earthing/ground