Need help identifying a 'sign'

[hammer]

My friend took this photo. He asked me the meaning of the purple "D" sign.
Could one of you tell me ?

Thanks


View attachment 17651

 

[CP9302]

That marks the de-rail for the siding. The yellow lump on the rail is the de-rail it self.

De-rails prevent cars from rolling out on to the main by de-railing them before the main in a controlled manner.

 

[hammer]

That marks the de-rail for the siding. The yellow lump on the rail is the de-rail it self.

De-rails prevent cars from rolling out on to the main by de-railing them before the main in a controlled manner.

Outstanding info ! ... thank you sir.

 

[UP2CSX]

Although, it's first one I've seen that color. Almost looks like a temporary installation.

 

[lmackattack]

Jim, up here by me all the Derails are painted yellow? with a red or yellow "D" sign near it

 

[Trussrod]

Say Hammer, Fred & Trent!

That's very interesting info that I wasn't aware even took place. I always assumed cars
left on a siding would have the brakes set to prevent them from rolling.

Interesting info for sure, too bad the image is so small and the resolution so low.

 

[jbaakko]

I see both purple & blue signs like that, or the long "Derail" sign like this:

The later of the two, in white with black letting is common too.

 

[jbaakko]

I have the Details West foldable derail, and I had to modify mine to be more like this:

All it required was removing the cast on brace so the derail would fold low enough to clear hanging equipment.

 

[hammer]

Thanks for all the additional input, folks.

 

[ChevelleSSguy]

Are these operated as part of a CTC system? Do they just make the derailer "on" or active I should say once a car is past it?

 

[fiend540]

So what are the basic rules when it comes to derailer usage, when/where they are used more specifically.

 

[UP2CSX]

As has been said, derails are used to keep a standing car from rolling on to the mainline in case the brakes fail. David is correct that the brakes are set when the car is spotted but it's not uncommon for a car, especially an older car, that's setting on stub track for a good bit of time, to start getting slack in the brake chains. Even then, the car won't usually roll unles the spur is on a slight grade. The derail is there to put the car on the ground before it reaches and fouls the main line track. Some derails also serve an opposite purpose. Little used spur tracks are sometimes in bad shape, and the industry it serves will sometimes pile up debris and trash around the track. The crew is supposed to visually inspect the spur to make sure it safe for operation and then report back to the dispatcher for permission to open the derail. Derailers are normally completely manual and not tied into any type of signal system. They are usually operated the same way as a normal switch. They can also be installed temporarily by bolting them to a rail, as in the picture Josh posted. Derails also exist because vandals will sometimes release the brakes. I've never seen a remotely operated derail that was part of CTC but I imagine, like all things in railroading, there's probably one out there somewhere.

 

[fiend540]

I guess I worded my question wrong, I understand the point of a derail but I am wondering when you would use one, or when you wouldn't, and by that I mean it doesn't appear to me that these are used at all industrial sidings at least not that I have noticed. So how is it decided on which sidings get them, and which don't?

 

[Rico]

You would use a derail wherever there is a danger of a car or equipment rolling thru a switch or other device and fouling the main or other track. Some, or even most sidings are lower than the main so they may not get one. Yards may also have derails, powered or otherwise, to prevent cars or stray locos from "getting away". I have a powered derail at the enterance to the paper mill on my layout.
There is a shortline here that had one put in right before the junction with the CNR after a wind storm blew some 40 plus cars a couple miles and onto the mainline.

 

[fiend540]

You would use a derail wherever there is a danger of a car or equipment rolling thru a switch or other device and fouling the main or other track. Some, or even most sidings are lower than the main so they may not get one. Yards may also have derails, powered or otherwise, to prevent cars or stray locos from "getting away". I have a powered derail at the enterance to the paper mill on my layout.
There is a shortline here that had one put in right before the junction with the CNR after a wind storm blew some 40 plus cars a couple miles and onto the mainline.

Alright so it's done basically on a case by case bases. Thanks for clearing that up