Sanding system controls

[ledwardz]

Hello,

wondering if someone could point me to some reading material for 2015 Q1b.

2015 1b. Describe the parameters of a sanding system and the control related to it for safe operation of the whole railway system (10 marks).

I know what a sanding system is but not sure what its getting at by control related to it for safe operation of the whole railway system.

i get the whole too much sand causes resistance between the track and the axle so there is residiual current in the relay coil which could potentially be enough to keep the TBC relay energised and hence cause overshoot/ collisions etc. but i believe this is what the end of Q1C is asking me so not sure what this question is actually after or how i am meant to get 10 marks for it.

2015 1C.  Discuss the effect on traction and braking of usin these controls and the implications for the train detection.

Thanks,

Lee.

[dorothy.pipet]

I probably know less about a sanding system, but assume that a train is used to put sand on the rails to increase adhesion in poor conditions. I also assume the sand needs to be delivered evenly at a set volume/weight per length of rail. Tell me if this is wrong as I imagine a train with hopper(s) feeding sand to nozzle(s) through some kind of variable valves.

It would be desirable for the sanding train to be able to travel (while sanding) in between timetabled traffic to keep the railway operating as normally as possible. That means that the train will be affected by Speed restrictions, red signals and generally not travel at a nice slow constant speed. A sanding system needs to be controlled to respond to the train speed in order to keep delivering an even coating (i.e. to provide constant sand per meter, by variable flow per minute)
It needs to switch off when stopped, it may need to change the angle of delivery nozzle(s) when the track has a curve or camber, it may need to warn when a hopper is blocked, nearly empty and so on. Failing to do this could mean erratic braking adhesion leading to possible SPADs; erratic TC behaviour which could release route locking or allow conflicting routes to set or clear signals in error; there may be issues with traction return currents owing to high resistance; and probably a load of other things I can't imagine. If uncontrolled, and the sand heaped up while stopped at a signal maybe a derailment could result.

Excess sand missing the rail may also affect track bed/ballast conditions, I don't know, but building up the ballast level was a factor in an incident where a signal post rusted through and the signal fell over (encouraged damp conditions and prevented inspection). Sand on the trackbed could make conditions underfoot even more difficult for those working on the line (maintainers for example), thus being a factor in slips/trips/falls accidents.
What about 3rd rail/4th rail electrified areas - presumably the sand must stay clear of the electrification rail or it will do damage.
What about a sanding train going over a Level Crossing - might you want to prevent the road from being sanded?

These are the sort of things you might be thinking of in terms of controlling a sanding system, and the consequences for signal engineers.
You might think about possible mitigation to protect the signalling system such as requiring sequential operation of track circuits, but is this disproportionate if the sanding is infrequent and/or well controlled.?

[ledwardz]

I probably know less about a sanding system, but assume that a train is used to put sand on the rails to increase adhesion in poor conditions. I also assume the sand needs to be delivered evenly at a set volume/weight per length of rail. Tell me if this is wrong as I imagine a train with hopper(s) feeding sand to nozzle(s) through some kind of variable valves.

It would be desirable for the sanding train to be able to travel (while sanding) in between timetabled traffic to keep the railway operating as normally as possible. That means that the train will be affected by Speed restrictions, red signals and generally not travel at a nice slow constant speed. A sanding system needs to be controlled to respond to the train speed in order to keep delivering an even coating (i.e. to provide constant sand per meter, by variable flow per minute)
It needs to switch off when stopped, it may need to change the angle of delivery nozzle(s) when the track has a curve or camber, it may need to warn when a hopper is blocked, nearly empty and so on. Failing to do this could mean erratic braking adhesion leading to possible SPADs; erratic TC behaviour which could release route locking or allow conflicting routes to set or clear signals in error; there may be issues with traction return currents owing to high resistance; and probably a load of other things I can't imagine. If uncontrolled, and the sand heaped up while stopped at a signal maybe a derailment could result.

Excess sand missing the rail may also affect track bed/ballast conditions, I don't know, but building up the ballast level was a factor in an incident where a signal post rusted through and the signal fell over (encouraged damp conditions and prevented inspection). Sand on the trackbed could make conditions underfoot even more difficult for those working on the line (maintainers for example), thus being a factor in slips/trips/falls accidents.
What about 3rd rail/4th rail electrified areas - presumably the sand must stay clear of the electrification rail or it will do damage.
What about a sanding train going over a Level Crossing - might you want to prevent the road from being sanded?

These are the sort of things you might be thinking of in terms of controlling a sanding system, and the consequences for signal engineers.
You might think about possible mitigation to protect the signalling system such as requiring sequential operation of track circuits, but is this disproportionate if the sanding is infrequent and/or well controlled.?

Hi Dorothy Pipet.

Really good reply and simple to understand, thanks very much. i will commit this to memory for the exam in hope a sanding question comes up.....

could you elaborate on the sequential operation of track circuits?

google tells me its track circuits with an interface to the locking system that applices sequential logic so that when an out of sequence detection occurs the area is 'quarantined'

cheers,

Lee.

[dorothy.pipet]

You should not expect to pass the exam by memorising answers - you need to be able to demonstrate to the examiners that you HAVE READ, UNDERSTOOD AND ANSWERED the question. Not answered last year's question.

Sequential operation is where you put additional controls on a track section so that it does not go clear until after a time delay unless the next track is occupied. For Network Rail it is detailed in the SSI8003 set of standards, but I couldn't say where off the top of my head.

[PJW]

You should not expect to pass the exam by memorising answers - you need to be able to demonstrate to the examiners that you HAVE READ, UNDERSTOOD AND ANSWERED the question. Not answered last year's question.

Sequential operation is where you put additional controls on a track section so that it does not go clear until after a time delay unless the next track is occupied. For Network Rail it is detailed in the SSI8003 set of standards, but I couldn't say where off the top of my head.

I would actually interpret the question (as presented here- I have not looked up the full wording) to be a sanding system on a particular locomotive or multiple unit train rather than a mass application of sandite generally, but I don't think it changes much.  Typically a freight loco might routinely apply sand when wanting good grip for particular acceleration, particularly if encountering slipping.

Dorothy certainly has included many things that are highly pertinent to answering the question, but her most valuable advice was certainly in her last post.  Every year's questions are unique; trying to pass the exam by going in with any pre-prepared answers is doomed to failure- the examiners have made clear on many occcasions that it annoys them intensely that they get answers that are clearly that to a previous year's question and they are very much on the lookout for candidates who try that approach!  There is no substitute for carefully considering the precise question asked and using your knowledge and experience to construct an answer to it.........

[ledwardz]

You should not expect to pass the exam by memorising answers - you need to be able to demonstrate to the examiners that you HAVE READ, UNDERSTOOD AND ANSWERED the question. Not answered last year's question.

Sequential operation is where you put additional controls on a track section so that it does not go clear until after a time delay unless the next track is occupied. For Network Rail it is detailed in the SSI8003 set of standards, but I couldn't say where off the top of my head.

I would actually interpret the question (as presented here- I have not looked up the full wording) to be a sanding system on a particular locomotive or multiple unit train rather than a mass application of sandite generally, but I don't think it changes much.  Typically a freight loco might routinely apply sand when wanting good grip for particular acceleration, particularly if encountering slipping.

Dorothy certainly has included many things that are highly pertinent to answering the question, but her most valuable advice was certainly in her last post.  Every year's questions are unique; trying to pass the exam by going in with any pre-prepared answers is doomed to failure- the examiners have made clear on many occcasions that it annoys them intensely that they get answers that are clearly that to a previous year's question and they are very much on the lookout for candidates who try that approach!  There is no substitute for carefully considering the precise question asked and using your knowledge and experience to construct an answer to it.........

thanks for the replies, i will check out this document to see if i can find anything.

I think knowledge learned from previous exam questions is interchangeable. Many of the questions are based around similar topics and i have seen questions repeat on more than one occasion. By answering previous questions you can apply this knowledge as appropriate. Besides having 20 years experience in different fields i really don't see any other way of passing this exam.