Overspeed protection

[veggie]

I am planning to have some simple over-speed protection for my 6/1.
I already have a solenoid actuator which I can connect to a flapper valve on the engine air intake.
When the solenoid is energized, it will pull a holding peg from the spring loaded flapper valve linkage and close off the air until manually reset.
I now need a method of sensing and actuating the solenoid.

I was planning on sensing the generator voltage output as my over-speed indicator.
1] Does this seem like a good proxy for speed?
2] Does anyone know of an adjustable voltage switch that could be adjusted to close it's contacts at a voltage of 130 vac?

Or....other ideas?

Cheers,
Veggie

[veggie]

I respectfully challenge your challenge       (this is getting weird! )

If the inlet air is cut off, then engine is dead. I agree that there is huge room for error if the air is throttled, but in my proposed layout, the air valve would slam shut 100%.

On your system, when an over-speed condition is detected, are you closing the fuel rack with a solenoid?

Veggie

[veggie]

I will consider shutting the fuel rack as well as the air.

Sorry to harp on the air valve thingy...but what allowed the engine to keep running?
Perhaps there was a minor leak in the system?

Fred!... can you fill us in on your attempt at an Air Inlet Shutdown?

Veggie

[dubbleUJay]

Jens, do you have pictures of your engine/setup somewhere on the net?

dubbleUJay

[veggie]

Just wondering....

If a Lister(oid) breaks one or more piston rings (especially an Oil Ring), and allow oil up into the barrel, can it start running on it's own lube oil?
If that's the case, then closing the rack will do nothing. The only way to shut down is by closing off the air intake.

Veggie

[Henry W]

You can use the compression release.
It might not be the best thing but it will stop a runaway.
Henry

[akatosborne]

Hi ,
Have a simple 4 protect device for this, over speed, high water temp, low oil pressure, high oil temp. Go to ebay and put in this number:  150378886401, Can use part or all the sensors.
Thanks
Tom
akatosborne@hotmail.com

[veggie]

Hey Henry,

You know our Changfa's are even more prone to this type of runaway.
A horizontal cylinder and bad piston rings can spell trouble.
I have heard stories of Changfas that started to ingest their own lube oil and ran away.
I'm not so concerned while our engines are still new, but I would like some foolproof protection as they age.
This is my reason for coming up with an intake shut-off valve.
Something simple and inexpensive. (Oh yes....and it has to look really cool!!)

Veggie

[Henry W]

Air shut off should work.

I just looked in the S195 manual and they say the engine can also be stopped by putting the decompression device into action if necessary.

Henry

[veggie]

Here's something interesting....

We have one of these on our diesel powered service vehicle.(Ford F350 Powerstroke).
The service technicians where I work are not allowed on Oil & gas sites unless the truck is equipped with a "Positive Air Shutoff Valve".
This is mandatory in Alberta.
There are 3 videos on this page which discuss air shut off valves on diesels.

http://www.rodadeaco.com/videos_why_you_need_an_airshutoff_valve_video.asp

Veggie

[veggie]

Jens,

Thanks for the link to the other site.
I tried it but the site was down. (Go figure !)
Will try again later.

Veggie

[Ronmar]

I was digging this up for someone else, but it appears relavant to this discussion.  http://www.macromatic.com/products/products.php?series=VWKPU

With a harmonically excited generator, I think voltage monitoring is another way of getting over/under speed protection as output voltage is dependent on generator RPM.  This relay should do that job, and has the added benefit of adjustable time delays to filter out possible short transients and reduce false activations. 

I think any shutdown scheme should fully close the fuel rack.  I think I would prefer the compression release over a intake flapper.  I have seen it fail in a GM application as the sudden vacume sucked the seals out of the intake blower and the engine continued to run on that air source and some leakage around the flapper.    Hot and worn rings can leak a little, and the rings are designed to resist pressure going downward.  If given a high vacume during intake by closing off the air inlet, it might be possible to pull in a little air up past the rings from the case...  By activating the compression release, it dosn't matter how much air or fuel is present.  It can't generate the heat to ignite it...

My .02   

[BruceM]

Like Shipchief, I'm a fan of the SOM approach of both decompression and rack closing for shut down.  

I get to use pneumatic cylinders with lots of force, so there's no chance of the rack not being fully closed.  To force the rack closed does take about 10 lbs, I recall.  I think I'd use one of the automotive motor driven shafts instead of a solenoid if I was to do it electronically. High force solenoids are huge power hogs, and it can take quite a while for the engine to fully stop.

My decompressor uses an air cylinder too- it has the force to lift the exhaust valve.  The SOM approach of putting a spacer into the valve lifter path (like the manual exhaust valve lifter) would need very little force, and could be RC servo driven (with overide springs in case the valve is closed when applied in either direction.

[Ronmar]

I wouldn't use the solenoid to close the rack directly either.  You are right, monster solenoids are power hungry and expensive:)  I would use a heavy spring to do that job.  The spring loaded shutdown lever would be held OPEN by a latching mechanism to start and run the engine.  Visualize a hammer and sear like in a firearm.  The small solenoid would either pull the trigger to trip the spring loaded rack closure, or the small solenoid would be energized all the time to hold the latch engaged.  In this mode, when it's voltage is removed, the shutdown lever is released to be close by the spring.  This same rack trip mechanism couild also mechanically slide the compression release block in place to lift the exhaust valve...

Same could be done with a small air tank, solenoid valve and air cylinders.  I think I would want a low pressure switch on the tank to give an alarm and to trip the shutdown cylinders at a point before an air leak disabled the system.  More complex, needing a source for compressed air, but a very elegant control system:) 

[BruceM]

I agree, Shipchief, for emergency shut down, rack closing the solenoid release of a 10 lb plus spring is a good solution with minimal power requirement.  It would also work for remote shut down if resetting the spring on startup is acceptable.

A solenoid pin which normally held and could releasethe end of the rack opening spring with power applied would also be OK, if decompression was also applied as insurance.  Again, this would require resetting on startup.

I also did some experiments with a "fuse link" brass wire holding the end of the governor spring. Applying 12VDC to the brass wire would "blow" the wire and release the spring. This did work well as a very simple emergency only shut down.

In my case I needed remote start and shut down without manually resetting, and already had air available, so I chose air cylinder actuators.

For an electric only rack closer which could be cycled without a manual reset, I could find nothing less than a linear actuator (about $75 for a 4 inch throw one on ebay) that would do the job. They have excessive force, over 200 lbs.

Bruce M