At airports, the fuel pump has an earth lead.

[flying dog]

I'm wanting to know the "standard" which defines how the earth is measured.

 

I'll call Standards Aust later on but anyone here have any ideas where I could look to find it?

 

Thanks in advance.

 

 

[Tomo]

Not real sure what you're trying to ask Flying Dog?

 

Are you referring to the Earth lead at airports, their length? or are you wanting to know how to measure our planet earth??

 

If it's the Airport fueling earth lead, it doesn't have a particular length, (Ie. That worry's the performance of it) As long as it's connected to the earth, and it's a conductive wire/lead, it will work no matter what length, within reason!

 

Sorry about the understanding of your question, you may need to clarify a bit more clearly what you would like to know:sorry: Or is it just me..?

 

 

[Guest watto]

Not sure on that one but I believe you can no longer fill plastic containers at petrol stations either without first placing them on the ground to earth them and as I am aware you cannot rock up with a 200lt drum and fill it on the back of a ute as there is no earth facility at the average site, this practice may be taking place at some locations but is supposed to have ceased. you can do this at the airport or a fuel depot though.

 

 

[Guest watto]

I agree Tomo, static earthing is not a coplicated process, you are simply giving spark an alternative more direct route and the leads are of course the simplest most effective way to do this which can be attached to any object.

 

The more important part is where the earth spike goes, and your local electrician or power supplier will be able to assist you with how that is measured

 

 

[davemac]

Filling 200 lt drums at servos has been banned for a few years as, supposedly they may not be earthed. But how is your car's petrol tank earthed? Through the hose is the answer, carbon filled rubber hose, and this by the nozzle touching the petrol filler neck. So if you keep the filler nozzle in contact with the 200 lt drum neck, then it is earthed; if you break this contact intermittently, like shaking the nozzle, you could cause a static discharge, ie, a spark. This was the supposed reason that a lady set fire to her car when filling a jerry can recently; apparently she stopped the fill, removed the nozzle to check how much was in the can, and up it went! I have tried to fill a 200 lt drum in my ute with a proper earth line connected back to the bowser but the console operater does not understand the theory and just says No. How the hell one lifts a full 200 lt drum back into a ute at a servo is beyond me!

 

I just use metal jerry cans at the servo, filled on the ground, and lifted into the ute when full.

 

 

[Guest watto]

Yep dave it is a hornets nest of different arguements, theories and exceptions but like everthing it is worst scenario driven.

 

 

[flying dog]

Ok sorry, it was toooo early when I posted it.

 

"EARTHED" is a bit vague.

 

What is the minimum resistance? How is it measured?

 

At a private airport the earth lead is a bit yucky. We want to make it better, but want to do it correctly.

 

As much as it is more to do with discharging the static between the tank and the container....

 

I am just looking for any "minimum standards" needed for aircraft earth points, their lowest allowable resistance to "earth" etc....

 

 

[GraemeK]

I noticed CASA gave an exemption the other day to QF so they don't have to earth the plane while refuelling - the QF argument was that their suppliers no longer permitted earthing.

 

BUT - the key was that the truck, the tank, the aircraft, anything else used had to be bonded together electrically (ie all at the same potential, but not necessarily at earth potential). Just as davemac said re the conductive hose.

 

 

[Guest ozzie]

The term 'earth' just really means that everything is connected t a single point so they are of the same potential resistance to ground.

 

regardless of 'conductive' hoses i would still use a cable to ground all equipment.

 

the weather we are having at the moment being hot and dry with lots of airborne dust to generate static makes it is the time for refuelling fires. there have been three fires in servos in Sydney and Melbourne over the last few weeks. Avoid wearing nylon. Since the dust storms every time i get out of my van i get zapped and gee i really hate that.

 

good quality 2.5mm insulated and coloured yellow/green, single or multi core wire is suitable for an earthing cable fitted to a good grip welding type clamp. make sure the bond to the pump is clean and unpainted use stainless bolts and washers. Be wary of those wind up reels fitted to the pump. they have a habit of losing the connectivity between the reel and the pin they revolve around. check regularly with an ohms meter between the pump and clamp

 

i also get into the habit of touching the bowser or earth leads to remove any static from myself before opening the fuel tanks or lifting the nozzel.

 

Ozzie

 

 

[flying dog]

Hey Ozzie.

 

(Back to what I am asking)

 

Yeah, well I am just wanting to learn the minimums required by law. I understand the problem and what is going on, but I think it would be a good idea to learn what is required BY LAW (be it there is such a thing) and use that as the starting point.

 

It is amuzing watching some planes fill up: They are fiberglass. The pilot puts the earth to the exhause pipe and then fills up the PLASTIC tank nowhere near the engine. It kinda doesn't work.

 

Getting a bit off the topic:

 

I have been to places where one suburb is at a different earth potential than the adjoining suburb!

 

Simply sticking a "rod" into the ground may not be the best. If the place in the ground where you stick it is too dry, rocky, etc, then it is not really an earth and though you may connect the plane to the pump with a lead, the other mentioned problems still exist.

 

Yes, I've seen places too where the roll of wire is not too well connected to the post and can nearly be lifted off. This too is a problem.

 

Sure these individual things are not problems and not "mission ciritical" for safe refueling. However, accidents usually happen when more than one thing fails in a not too good system. Then all hell breaks lose.

 

 

[Captain]

With my J230, there is a long SS wire in each tank that just lies in the fuel, and both are earthed back to the engine via the post next to the tank.

 

In my case, when refuelling I also lie the wire that attaches and retains each fuel cap over the post so that the system is eathed as much as possible via the earth post at each fill point. I then attached the fuel system earth clamp to the exhaust + clamp the one from the bouzer nozzle to the earth post at each fill point.

 

I reckon that is about as good as I can do.

 

 

[Guest ozzie]

I have in my possesion for work the 'wiring rules' from Standards Australia

 

AS/NZS 3000:2007 on page 206 it covers two sections regarding earthing. one is Potective Earthing 5.2.1,theother section is 5.2.2 Functional Earthing there are alsosome tables for thecorrect sizing/ material for the conductor rods too long winded to copy here best to grab a copy from a sparky and look it up.

 

 

[flying dog]

http://www.casa.gov.au/wcmswr/_assets/main/rules/1998casr/139/139m11.pdf

 

page 13 - 15 seem like nice reading.

 

Ozzie, shall read you new post after posting this.

 

Thanks.

 

 

[Guest Gomer]

I can't help with the legality side of things, but on the reality side... The wiring rules don't really apply in this case, as they are sized to carry as much current as the mains supply can provide in a fault situation. Hence, if a mains sub-circuit is rated at 16A, the the related earth has to be similarly rated. In the case of refuelling, all that is required is a bond to drain away the static that may have built up. Once it is drained, even a very high resistance will keep it that way.

 

One of the good reasons for having a separate earth strap is simply to create the spark (if there is one) before either opening the fuel caps or bringing the hose near the a/c. If you rely only on a conductive hose, you're still going to get the initial spark when the hose is first touches the body.

 

Didn't really answer your question, but hopefully it was helpful background... :)

 

 

[davemac]

Hi Gomer,

 

the earth wire applied before fuelling aircraft has two purposes, it dissipates static electric charges built up on the skin due to the air rushing past it in flight, and static charge also build up during the fuel operation itself by the fuel rushing along the hose. This is why the aircraft is 'earthed' to ground and "earthed" to the bowser. No electric potential difference anywhere. In days gone by, this whole operation may been have carried out on a totally grassed surface, often a poor conductor.

 

The conductive hose in servos is only considered for static buildup during the fuelling operation as the initial action of opening the tank cap will 'earth' out the tank via the person standing on the ground doing the refuelling.

 

But, I must admit, I have often thought of that zap I get, as I put the key in the car door after walking across from a shop with a carpeted floor. I seem to get the biggest zap when returning from my local Dick Smith!

 

After re-reading your post yet again, this is pretty much what you have already said, but my take on it may help another reader to see it more clearly.