Cleaning main tank?

[PA1195]

Algae, bugs, crud, and corrosion like moisture. If available at the bottom of the tank or above the fuel they'll set up housekeeping. Common with turbine engine fuel that sometimes needs ice inhibiting additives like PRIST. Isopropyl alcohol can keep things dry.

Gary

[Hank Jarrett]

Larry, I remember using those vacuums in the Navy. They worked great and didn't carry the explosion hazard of a shop vac. I also remember a radiator shop guy telling me they had a car gas tank "WHOMP!!!!" on them that had sat open for YEARS. He was the guy who told me most shops flood the tank with CO2 now to prevent explosions. It isn't a "high yield" explosion, More like a long low thump, but it does tend to try to make the tank a sphere and split the seams. The way he talked he never wanted to be around a second time for it. The CO2 doesn't get rid of the fumes, but there is no O2 to support combustion.

Hank

[lawheelock]

Hank, a practical way to flood the tank with CO2 is to get if available, some dry ice and put it in the tank. I did some welding for a drain on a new 50 gallon tank that I had for my pickup to transport unleaded ethanol free mogas to my plane. I got some dry ice and never had a problem. I am not sure that the tank had ever had gasoline in it but I was not taking any chances. Down here in deep south Texas dry ice is often available at WalMart or Sams for the folks that come from deep down in Mexico to shop and transport frozen food back to whereever they live.
I have never inquired, but it is possible that Swans would sell someone a little dry ice as they have a big CO2 tank at their truck base location to use in their delivery trucks.

Larry

[astjp2]

To do it right, pull the tank and take it to a radiator shop, they can remove any corrosion, repair any damage and reinforce the bung for the fuel outlet. That is the place they most likely crack. It needs to be an old time shop that actually does repairs. If you need to replace the elbow screen or header tank valve, let me know. Your IA should be recommending the same thing. Tim

[Hank Jarrett]

Dry ice was what the guy I talked to used. I don't think he actually put the dry ice into the tank, but used a container that had a hose that led to the tank. Something about not wanting to cool one area where the dry ice was in contact with the metal causing stress to the tank joints. Pretty simple set-up. Just a foam cooler with a hose to the tank. The CO2 is heavier than air.

Hank

[Scott]

There is a correct procedure for safety performing fuel tank work. Most aircraft fuel tanks cannot be removed so manufacturers have developed procedures to safely purge fuel tanks for service. Avgas is easier to deal with compared to jet fuel in terms of tank prep but obviously avgas is more easily ignited.

Basically the tank is most dangerous when the fuel vapour is mixed wit air. So a tank with fuel in it, and saturated "air" space is relatively safe, and a fully purged tank is safe, but there's a point during purging were the fuel/air mixture is in the danger range. The danger when circulating air, whether by shopvac, fan, or ventury, is the risk of creating static charges. So the number one precaution is to ensure everything is grounded.

There are "sniffer" testers that measure the oxygen content and therefore flammability of the gas mixture in the tank. Testing is done during the purging process and continues to ensure a safe environment once work commences. So next time you're about to crawl into a fuel tank this is what needs to happen first!

A Taylocraft tank presents no significant challenges. There are no baffles, nooks or crannies to deal with and avgas or mogas evaporate quickly.
1. Make sure the aircraft, tank, and any air-moving equipment is properly grounded.
2. Completely defuel the airplane,
3. pump air into the tank (as opposed to sucking potentially volitile mixture through your equipment) until everything is dry and
4. keep the air flowing as you work.

[astjp2]

LFL and LEL need to be outside the threashold, plug in a vacuum cleaner to the exhaust port and let it run for an hour or 2, if you smell active gas, its not enough. or just take it to someone who specializes in fixing them, like a radiator shop. I cant fix it for the same price they can. Tim