impeller material for use with jet A-1 Fuel

Don't think it matters much from the perspective of compatibility with A1. BTW, I'm surprized you have been requiring stainless. I don't know of any specific need to do so. Is there some reason that you have been using SS? Perhaps you should investigate why you have been doing that and why it was (apparently) specified for this particular pump, as you may want to consider that whatever reasons you find there might have some bearing on the selection now.

BigInch-born in the trenches.

Hi,

Now I have to find out why the SS impeller was specced in first place. Pump Mfger says brass impellers are standard for petroleum jobs. We (Govt) have std specs for tank farms and dispensing facilities.

Also we have, for some reason, stainless piping starting after the filter unit in our standard set-up for dispensing bldgs (this is for small northern airport).

Do we need a relaxation unit for Jet A1 to reduce static after the filter? We have had one in our std. but i am told it is not necessary nowadays.

Now that you have described your system a little better, it seems to me that the stainless steel in not specified to protect the pump and piping from a corrosive product but instead to protect a clean product from contamination with rust, weld slag or pipe scale. We specify all stainless steel piping, valves and fittings in lube oil systems for large compressors. But we will allow carbon steel before the filters. Your situation sounds the same. If you are dispensing fuel for aircraft, cleanliness is vital. But if you are filtering the product stream, I don't see any problem with a non-stainless material for a pump impeller. I work in the refining industry. API process pumps don't use brass or bronze impellers. Cast iron is common in older pumps. Cast steel is better since it can be repaired. But because of the relatively small incremental cost, we normally purchase 12% chrome impellers (CA6NM). It only costs perhaps 20% more than cast steel. It can be weld repaired, if needed. It has more corrosion resistance. I am not sure about the affect on resisting cavitation damage. Cast iron is probably better than either cast steel or 12-chrome.

I am not sure what a relaxation unit is. But static buildup can be a serious problem. We had a tanker truck explode a few years ago when loading a grade of #1 fuel oil. We are now required to inject a conductivity improver chemical to help prevent this. I would not suggest eliminating any system designed to control static unless you are very sure you know it is not needed.


Johnny Pellin

Relaxation chamber is to remove static-it is a tank which holds the fuel (30 sec) to diminish static between filter and point of discharge. In our std. buildings it is placed on outside of the building-fuel is piped from the filter/separator to the relaxtion chamber then back into bldg to pump and discharge. Based upon your comments and the research i have been doing we certainly should not remove that..

If API uses brass or bronze impellers for process pumps shouldn't our small transfer pump (Gorman Rupp) then be made of one of those materials? Their tech person told me that brass was standard with their fuel pumps for petroleun product use...

Jet fuel distribution at the airport should not require any special materials for the jet fuel or av gas itself. Personally, I don't think you should be worried about impeller bits either as there is much more danger from contamination during the last truck haul or last pipeline transport, or last tank contamination, than what you would ever have from a flake or two off an impeller of any kind of material. Interestingly enough I have found one obscure reference to the US Army mobile field AC fuel delivery pumps being supplied with brass impellers, but with no reason given, Static electricity?? I also note that in addition to carbon steel, they will use stainless, aluminum and FRP pipelines too (for weight restrictions delivering to field and easier field handling I presume). Still the product will probably be filtered again on the truck delivering to the aircraft's tank. I think SS piping may be more for corrosion protection from exterior sources, taxi-way salt for ice control, de-icing spray drips and simply ease of maintenance (no paint required) to keep up presentation. Seems to be favored by USAF. There should be no chemical or physical requirement for SS or brass internals for fuel pumps, however with that USArmy pump, that should be qualified with IF they are not required for some anti-static electricity reason.

I don't get involved with final distribution at the airport, but I know that anti-static treatments (Static Dissipater Addatives, SDA) are chemical additives that must be added after the last terminal tank (pumping tends to disassociate that chemical) and is used with JP-8 = Jet A= Jet A1. It is not added to JP-5 (US Navy), so the practice there is totally relying on limiting fill velocities to < 1 m/sec and doing slow fills (filling >10 minutes), bottom tank loading, static grounding are common handling techniques, as is the case for all aviation fuels, due to both the possible build up of static on the AC and the fuels too (which can reach 50 kV). "Relaxation" by letting freshly pumped fuel sit in tanks for 30 minutes or so, I believe is also common, especially in cold dry climates, so I wouldn't eliminate that practice. With the newer fuels and additives, I think some of that practice might be left over from previous days when AC fuels were more explosive, but with up to 50 kV possible, I certainly won't say its not worth continuing to do it.

It would be interesting to find out if the pump vendors do not routinely supply brass to other AV fuel clients. Could let us know what you find out there?

BigInch-born in the trenches.

The planes fuel up right from the dispenser bldg -we have 100 ft hoses. The community airports and planes we are dealing with here in NWT (northern Canada, north of 60) are small.

My very first job was fueling private planes in Houston, Tx. in 1968. I still remember attaching the static grounding wire to Arnold Palmer's Learjet, but we had no relaxation tanks there.


BigInch-born in the trenches.

Maybe you're interested in these. Here's some fuel facilities and handling practice info from USArmy,

Fuel Facilities

Static Electrictiy

Aircraft fuel static safety and cleanup
BigInch-born in the trenches.

thanks! I have not had chance to study them yet, got side-racked.. But have got word from the fuellers at City Airport here that they want relaxation chambers on the rates of fuel transfer they use.

Good idea.

BigInch-born in the trenches.

Exxon aviation reports: neither of the products you mentioned in your email (i gather they mean copper and brass) below are recommended for a Jet A-1 pump impeller. Copper and brass fittings are not suitable for use with Jet fuel as they adversely effect the chemical properties of the fuels.

Only other alternative on that model of fuel tranfer pump is grey iron, but i could not get hold of Exxon rep again to see if that would be satisfactory

As well as zinc/galvanized piping and components not being suitable.

I don't think gray iron is a problem, but I myself have never used anything but low carbon steel. Seems strange that its not available.

BigInch-born in the trenches.

Now I am beginning to see why we specced stainless: Gray iron, the contractor says, will spark (why more than other metals? and why would it spark in pump if no air or water in there- though i guess it is possible as its in the line direct from storage tanks, before filter/separator.

That's (obviously) news to me. I would guess it must have a high(er) dielectric constant.

Perhaps the pump could be at partial levels when starting.

BigInch-born in the trenches.

All metals have an infinite dielectric constant though, don't they? .. true about the pump with partial levels when just starting to run...Anyway, latest in this saga is we are going back to contractor to ask him to find a similar spec pump with SS impeller, which I probably should have done in first place.

No they're different, due to the number of extra electrons in the atom. Gold, Siver, Copper are the best (common) electrical conductors. I think it also roughly corresponds with the individual metal's heat trans coefficients too.

BigInch-born in the trenches.

oh you mean as in conductivity, yes different metals would be different
i looked them up -- it's true SS is low conductivity , and iron is more conductive than brass- tho i am not sure where cast iron stacks up.

ya, that's it... apparently my conductivity is running low.

BigInch-born in the trenches.