Re: Which type of spark arrester WORKED the best?

I can't speak for wood or anthracite coal, but here is what I have learned about soft coal burning.

The smaller the cinder the less likely it is to start a fire. The cyclone front end works by breaking up the cinders before they go up the stack.

The smaller the openings in the cinder bonnet the smaller the cinder that can escape.

The heavier the wire gauge the longer the bonnet will hold up before being ripped apart by the exhaust blast.

The more transparent the cinder bonnet the better the draft will be.

Here is the dilemma. Small opening heavy wire gauge destroys the draft. Large opening heavy wire gauge doesn't stop the large cinders. Light wire gauge and small openings the bonnet plugs up and does not hold up.

The goal is to maximize both wire gauge and transparency.

Here is what I learned over the years. The cinders are roughly spherical or cubic in shape.

Instead of using a screen with a square opening between the wires a screen with a long rectangular opening will not allow the cinders through until broken up enough to pass through the minor dimension of the opening.

With this in mind at the C&TS we make screens with relatively heavy gauge wire but long rectangular openings. The result is a bonnet that maximizes both transparency and durability. That said we still replace the tops of the bonnet at every boiler wash. We could probably still make improvements by reducing the diameter of the bonnet and making it fit more closely the diameter of the stack.

There is still the problem when simply sitting over night. With a lazy fire the soot does tend to plug the bonnet. A taller bonnet or opening up on the blower from time to time would probably help with this issue. When the locomotive is working the soot issue disappears.

At the Roaring Camp the bonnets were hinged and could be opened up when not running. A hinged bonnet would allow the fire to be banked wiwthout plugging up and causing the smoke to come into the cab. Roaring Camp burned oil so there were no cinders. However the mountain was quite dry in the summer and heavily forested. We sanded the flues a lot and it was possible to break loose red hot carbon which could start a fire.

John Bush



Edited 1 time(s). Last edit at 02/23/2018 12:30PM by John Bush.