Question About Stressing When Removing Adjustment Switches

[Alex Neia]

Hello all

I have some questions regarding stressing when removing adjustment switches.

1) My first question is this:- On the overground what is the length of a stress transition adjacent to adjustment switches.
• Is it 180meters either side of the adjustment switch or
• 90m either side of the adjustment switch or
• 90m or 189m on one side of the adjustment switch.

2) My second question is when removing adjustment switches I need to pull a minimum of 180m either side of the pull point according to NR standards. The bit I do not quite understand is that NR standards states that I need to carry out stressing 180m into the existing CWR beyond the welded jointed on the CWR side of the adjustment switch.

I do not really understand what it means when it says …”beyond the welded joint on the CWR side of the adjustment switch” can anyone explain??

In the context of an example I will be carrying out stressing where adjustment switches will be removed. Focusing on just the CWR side of the adjustment switch for now; the distance from the tip of the tongue to the weld is 12m. In this case does my 180 start from this weld moving away from the tongue???

If my thinking is correct then a follow on question would be this; in other adjustment switches the distance from the tongue to the weld maybe more than 12m or less than 12m which means that I will be stressing into the existing CWR 180m minus the distance from the tongue to the weld. This seems incorrect to me can anyone throw any light on this??

Attached is a diagram of what i mean.

(Assume standard resistance fastenings)

Thanks.

 

[miikey]

You must stress at least 180m into the existing CWR when you remove adjustment switches. This is becuase of the stress transition site that islocated at adjustment switches.
I take it you will be installing new rail i.e. Level 2 stressing?
You need to have your Pull Point (PP), then your Inner Tell Tall 180m into the CWR Side, then you can stress any length of rail (up to 1620m) into the Jointed Side.

I would measure the 180m from the tip of the adjustment switch, as this is where the stress transition is.

Hope this helps,

 

[The Informer]

Can i ask why are these adjustment switches being removed? It doesnt make sense to remove them unless the jointed side is being converted into CWR or a renewal.

I always remember it as "180m into the existing CWR"

 

[transportphoto]

I would suggest you speak to your colleagues, superiors or trainers before undertaking any work based on suggestions made on this forum. The work you do is Safety Critical, you don't want to breach safety because the instructions on here are wrong. They might not be, but you can not be certain.

TP

 

[The Informer]

I'll second that. Dont be afraid to ask in work, i aint. You"ll look a bigger clown if you try and second guess.

 

[Ploughman]

Is NR/L2/TRK/3011 available online?

 

[Trog]

Can i ask why are these adjustment switches being removed? It doesnt make sense to remove them unless the jointed side is being converted into CWR or a renewal.

There are also many sets of un-nessessary adjustment switches around the network. Left in by those to lazy to remove them, or installed by people who did not know what they were doing in the first place.

I have seen two that were installed/left simply to avoid the bother of having to stress through level crossings for example.

 

[Alex Neia]

miikey

but what does the …”beyond the welded joint on the CWR side of the adjustment switch” mean?

what does it refer to?

 

[The Informer]

Its the welded joint that was used to join the breather rails to the CWR.

 

[Alex Neia]

Informer

So when it states;

"...180m into the existing CWR beyond the welded jointed on the CWR side of the adjustment switch"

Then this must mean that the 180m must start from this weld towards the CWR would you agree.

I ask because most people believe that the 180m starts from the tip of tongue of the adjustment switch towards the CWR and fail to mention the bit that states …”beyond the welded joint on the CWR side of the adjustment switch”.

 

[miikey]

I don't see why it would be the weld as apposed to the Adjustment Switch tip. The weld doesn't hold any stress nor does it prevent the stress transition from spreading. I would class the switch tips as being the start of the 180m stress transition.
ask at work, what do you do?
Contractor?

 

[chappers]

Its been a couple of years since my L2 lapsed, but if you can't get a straight answer from anyone the best thing to do would be to stress 180m back from the weld that joins the adjustment switch to the adjacent rail. There is nothing worse from a compliance perspective than checking the documentation the following morning and seeing that the track has been under-stressed by a tiny amount.

Stressing 180m back from the weld will only add 18.288m maximum (probably even less) onto your total pull in one direction. So assuming you are now doing a 396m pull in both directions, you'll still key that up quicker than the time it takes for the welders to drop their tensors - so it makes no difference to the work carried out, but ensures that you haven't under-stressed.

Of course, the best thing to do is seek clarification from the responsible engineer

 

[Alex Neia]

I don't see why it would be the weld as apposed to the Adjustment Switch tip. The weld doesn't hold any stress nor does it prevent the stress transition from spreading. I would class the switch tips as being the start of the 180m stress transition.
ask at work, what do you do?
Contractor?

miikey

I'm a contractor. I carryout stressing for NRail and LUL. I have never stressed where i will be removing adjustment switches so when i checked Nrail Standards i couldnt understand what "...180m into the existing CWR beyond the welded jointed on the CWR side of the adjustment switch" meant.

After speaking to 2 different track engineers and PTOs they have all said that they do not know and they will get back to me - but they never do.

What is the official answer to this? does the 180m start from the tip of the tongue or from the weld??

Also do i still need to add an extra anchor length (normally 90m) to my 180m? as per page 18 of the 3011 standard?

Thanks

 

[Ploughman]

If the standard says 180m from that welded joint, on the existing CWR side of the adj sw. Then that is what you must do. This 180m will be in addition to the length of pull into any new CWR.
The distance to the switch tips can be ignored as you are stressing to remove them and they will not be there will they?

 

[Trog]

It is an interesting requirement though as to my knowledge the standard FB type Adj Sw's have been made in at least three different lengths over the years, and which type you had would make no difference to the stress transition. But as at the worst it only adds 30'-0" to the unclipping compared to measuring from the tips. You would be a fool to risk trouble by not doing it, even though it does not make sense.

Just a thought I know of one adjustment switch where the blades are attached to the CWR with IBJ plates, and the first welds are 200 yards away. I think that one would be one to take to the boss to ask about a derogation.

 

[Ploughman]

There are also a number with standard plates and non Hi Tensile bolts plated on the CWR side of the switches.