There seems to be a mixed view as to where to instal the fuel shut off valve when installing a turbine, hence the poll, just a simple 'before' or 'after' should do it.

marcs

After the pump for me.

I would tend to believe that it doesnt make a difference. either before or after, with the valve closed, fuel will not travel through the fuel lines.......

I like it after since any restriction in the pump suction has the potential to produce problems with fuel flow. For the same reason, you don't want to use any 90 deg fittings or other sources of restriction in the feed line to the pump. Also, the larger the line sizes the better.

The downside of putting it after the pump is the pressure build-up if you forget to open it and the potential for a line to burst and spray fuel everywhere.

PaulD

Personally...... BEFORE!
After can be a disaster should you close the valve in an emergency and the pump is building pressure.....Line burst and fuel everywhere. It has happened! [X(]

It depends on the type of shutoff.If it is festo,after.Festos are designed for pressure operation.I have seen them suck air on the suction side of the pump.What Todd says is true,and I have had fuel line explode from pressure,but if I put the shutoff on the suction side,I use the Jetcat type,so it can't suck air.

I put one on both sides for saftey reasons. Never a problem.

Me & my friends put them after the pump. What we do is make them servo driven as Oz rules require
a manual & radio operated (independent of the engine electronics) shut off, we hook them up to the failsafe.

With this setup you can use just one valve. - John.

After the pump is my preference (for a quick, clean shut-down), but the BMFA COP doesn't agree...

Quote:

B. Gas Turbine Protection and Control
B.1 Start up and static running

Where engines are being run statically, on a test bench or during start up procedures in a model aircraft, boat or vehicle, a manual fuel shutoff mechanism must be provided. This mechanism may take any suitable form such as a fuel valve or electrical switch to cut power to the pump, but must be independent of the normal throttle control. Where a fuel valve is used in a liquid fuel system it should be located in the low-pressure part of the fuel line, between the tank and the pump. In a self-pressurised (gaseous fuelled engine) system it should be located as close as possible to the engine to ensure a rapid shutdown.

B.2 Operation under remote control,
The following paragraphs apply only to engines that are operated remotely, such that the manual control referred to in B.1 above is inaccessible.

B.2.1 Shutdown mechanisms.

The engine control function must include an independent fuel shut off device in addition to the valve (gaseous fuelled engines) or pump speed controller (liquid fuelled engines), as used by the throttle control.
The fuel shut off device could be a solenoid valve or a servo operated valve in the fuel line, in which case the considerations in regard of positioning given in B.1 above should apply.
Alternatively a relay, servo operated switch or additional transistor in the pump circuit may be used. Engine control units (ECUs) driving fuel solenoid valves should meet this requirement.

End quote:


Cheers,

Dick

Thanks for the replies so far on this guys, seems its a very personal thing.

My concerns are as follows, if you place the shut off before the pump there are two possible issues, firstly with large turbines drawing high fuel flow like a P200 you could 'restrict' the fuel delivery and place additional loads on the pump, second when you shut the valve down the pump will deliver the fuel still in the pipe work to the turbine so shutdown is not that instantaneous.

If you place the shut off on the turbine side of the pump you potentially can create the 'big bang' scenario of burst pipes and fuel everywhere, however the turbine shutdown should be relative fast, and fuel restriction is likely to be less (those in the know please confirm this point)

I am edging on the 'after' the pump option on this current build based on your comments, all of which really appreciated - KEEP THEM COMMING

marcs.

Yes Marc, the restriction will be better handled on the pressure side of the pump.
Being able to shut down the supply of the pump ( ie valve before the pump) will only be interesting in case of a pump going uncontrollable at full voltage.
I've never seen this happening personally but there seem to have been a few cases...

I have seen it and it is a very UNCOMFORTABLE feeling, especially when dealing with someone else's plane and you don't know exactly where equipment is located to stop the "flow". I admit, it is a very rare event as evidenced by the replies here; but if you ever have been involved in the situation, I'm sure the poll would be reversed.

tothemax may have the best solution; before AND after.[8D]

R/
George


P.S. Oliver, I'm coming through Dubai on 2/14.

I'm having a hard time envisioning a scenario where the fuel pump is running out of control and the ECU does not command the solenoid valve (down stream of the pump) to shut off and cause the same result as closing a manual valve in a similar location. Do you guys who put your shutoff valves before the pump also put the solenoid valves there? I notice that JetCat and JetCentral manuals show both valves after the fuel pump.

I have personally never had the occasion to (or seen anybody else that I recall) shut down a turbine with the manual shutoff valve. I would like to hear the particulars of instances where guys had to do it.

Since the larger 6mm shutoff valves I am familar with are Festo types, I don't like to use them on the suction side. I like to use the barbed Jetcat style 4mm valve after the pump.

Craig

I really don't understand why you need to install a manual shut-off valve in the first place???
I know it suppose to be a AMA rule in the US, but technically speaking we have already solenoid valves that are "fail-save closed" types.
A lot of my friends fly's for many many years turbines and never had problems in emergency shut-down situations or with refueling the plane. Anyway, I understand you have to install one in the US so my opinion is to install it after the pump.
The suction side needs to be as less restricted as possible and also the chance of sucking air (via the connections of the manual valve) is eliminated.

Hey Craig,

The ONE time I have seen it, the ECU "fried" and it wasn't commanding anything at that point other than supplying voltage to the fuel pump; the only thing that stopped it was unplugging the battery from the ECU. Nothing more than soaking everything with fuel happened, but it could have been much worse! Like I said, it is VERY RARE and obviously not many have seen it happen, hence the replies and votes.

Not sure about others, but my solenoids are after the pump and IF everything is working "properly" then all is well; the manual shut-off is before the pump for me in case of the above mentioned scenario, despite the extremely miniscule chance of it happening to me. I have never had a problem with it in that location, but I haven't run a turbine with more than 36#. My Mibo may require me to change my set-up due to component location, but I'll cross that bridge when I get to it.

George,

Thanks for the details. I hate to think what would happen if an ECU went crazy like that with the engine running, on the ground or in flight. Glad it's rare but with electrical things I guess almost anything can happen.

Craig