Thursday, Oct 02, 2014 at 20:04
As already stated, it's the method and type of fuel storage that is where the main problems start.
Many older servos or poorly-constructed servos have underground tank breathers that are located at levels where floodwaters can enter the tank via the breather.
Floodwaters carry mud as
well as water. Once floodwater enters a tank it will always be suspect.
Good servos have breathers on standpipes that are at least 2.5M-3.0M above the ground.
Corrosion is also a huge problem with underground tanks in servos. There are still many old underground fuel tanks around that were installed in the 1950's and 1960's - when tanks were merely coated with bitumen and dropped into a hole in the ground.
Acid soils and groundwater eats under the bitumen coating and into the tanks metal, and they start to let fuel out or let groundwater in.
Here in the West, the Mines Dept (now the Dept of Mines and Petroleum) controls the installation of, and oversees leakage from, underground fuel tanks.
The leakage of excessive amounts of fuel from underground storages (particularly in the sandy soils of the coastal sandplain around
Perth, led to some heartburn in the DoMaP when high-level carcinogens such as benzene (from petrol) were found to be contaminating underground aquifers in the aforesaid coastal plain.
As a result, detection spears are inserted around every underground fuel installation, and as soon as leakage is detected, servo owners are directed to remove and replace the tanks immediately.
They can opt to just remove them if they wish to cease using the site as a servo.
In inland areas where the soils are usually heavy or gravelly clays, leakage is less of a problem, but the corrosion problem is still there.
Servo owners are obliged to report any leaking tanks found, under environmental contamination laws - but there's no requirement for them to report on any tank that has contaminated fuel in it.
Nowadays, new tanks are installed within an impermeable geo-textile liner which is filled with coarse sand before the tank is installed (in the sand), and permanent spears are inserted into the sand between the tank and liner, to pick up any leakage.
If any leakage is found, that tank is taken out of service immediately.
Double-walled fibreglass tanks are becoming an industry standard - but we have a long way to go before we can replace all steel underground storage with fibreglass tanks.
In addition, a fibreglass tank is still prone to fuel contamination from damaged piping, or through water getting in through tank vents - although they are far better than steel tanks.
Envirotank
Tank installation and other associated news and developments in this field is overseen by APICA (Australian Petroleum Industry Contractors and Suppliers Association).
APICSA
It's generally hard to find out when the tanks of the servo you're dealing with were last replaced (unless you saw them being put in!) - but as a good rule of thumb, if the tanks have been replaced in the last 20 years, there should be no problems with fuel contamination.
The last 20 years is where the installation of underground tanks has really been "smartened up" with tighter controls and better designs and layouts.
Most of the contaminated tanks are the ones in the older seaside suburbs, and the ones in old country servos, where they are possibly 40 and 50 years old.
Even when I was travelling around Europe a couple of years ago, I received strict instructions from car hire companies to avoid specific servos. I got the impression it was because of contaminated fuel - of course, it could have been because of fuel substitution rackets (such as the toluene racket of a few years ago, here).
Of course, it's not the first time that a tanker has accidentally dumped petrol into a diesel tank, despite clear markings. It even happens in refineries.
I had a fuel distributor who told me many years ago he'd bungled a fuel refill and mixed serious amounts of diesel and petrol.
He just pumped the tank out and put it back into his bulk diesel depot tank to reduce the dilution.
AnswerID:
539812
Follow Up By: Axle - Thursday, Oct 02, 2014 at 21:23
Thursday, Oct 02, 2014 at 21:23
Hi Ron,..Don't let to much knowledge out around here it falls on deaf ears..lol., But mentioning old fuel storage tanks, our local servo got to the stage where the the tanker could only half fill the diesel tank,.. the other half was water!!.... It was like that for years,..Diesel floats on water No probs...LOL.
Cheers Axle.
FollowupID:
825469
Follow Up By: Ron N - Thursday, Oct 02, 2014 at 21:54
Thursday, Oct 02, 2014 at 21:54
Axle, I don't understand how that could happen, it sounds like a fair bit of legendary BS to me.
The reason being, the suction spear for the pump on underground tanks is screwed in place, and it reaches the bottom of the tank (see the Envirotank link above for diagram) - and it sucks from the bottom of the tank.
This is what causes all the fuel contamination, because all the crap settles on the bottom.
For a pump on an underground tank to be able to just suck the diesel off the top of any water in the tank, it would need to have a floating suction foot valve that floated on top of the fuel.
I do not know of - nor have I ever seen - any underground fuel tank that uses or used a system like this.
I have seen some blokes in a country town doing some digging with a backhoe, in a forecourt of an old industrial buidling, only to find a gusher! (of water).
It turned out that the place originally had an underground fuel tank - but the pumps were removed long ago - and the tank filled with water to prevent collapse!
When the backhoe bucket hit the
old tank, it released a gusher of water, making the blokes pack themselves, thinking they'd hit a water main!
Cheers, Ron.
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Follow Up By: Axle - Thursday, Oct 02, 2014 at 22:09
Thursday, Oct 02, 2014 at 22:09
Ron you are correct in your thinking,.. But what goes on at servos'
especially older ones, and different owners have different ideas, believe me!!....Many a tank I have pulled out....will say know more.
Cheers Axle.
FollowupID:
825474
Follow Up By: Slow one - Thursday, Oct 02, 2014 at 22:27
Thursday, Oct 02, 2014 at 22:27
Above ground tanks are the greatest source of water contamination through heating and cooling causing condensation, trust me.
FollowupID:
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Follow Up By: Ron N - Thursday, Oct 02, 2014 at 22:41
Thursday, Oct 02, 2014 at 22:41
Slow one - Yes, that's true, even more so if tanks are low on fuel and there's more room for moist air.
That's the reason you always refuel tractors and equipment at sundown when you knock off, so there's less room for condensation build-up.
However .. above-ground tanks have a simple solution to condensation build-up - they can be easily drained (and should be), on a regular basis! - just like your air compressor tank!
However, trying to extract a build-up of contamination from an underground tank is nearly impossible.
Underground tanks rarely suffer from a great deal of condensation build-up, because they're always at a very steady 15 deg in the ground - and that temperature never alters more than a degree or two, and over a lengthy period, when it does.
It requires a substantial variation in temperatures on a daily basis, plus extremely moist air, to enable sizeable amounts of condensation to build up, in above-ground tanks.
FollowupID:
825478