Why do class 67's tick?

ANDYS · 9 Mar 2015

Sorry for what might be a simple question but why do class 67's click when they are parked up?

Andy S

RailUK Forums

Iskra · 9 Mar 2015

I don't know the answer, but I do know that it's not just 67's that do this, lots of loco's seem to.

ANDYS · 9 Mar 2015

Iskra,

I just happened to have seen two 67's at Doncaster yesterday doing it.

https://www.flickr.com/photos/66737297@N06/16766888601/

Andy S

GB · 9 Mar 2015

Compressor drain valve perhaps?

gazthomas · 9 Mar 2015

If it's like first gen diesel locos it will be the air reservoir venting I think

ash39 · 9 Mar 2015

Spirax valve. Seems most noticeable on electrics, and 67s as the op suggested.

ANDYS · 9 Mar 2015

Thanks all but what does a Spirax valve do?

I just googled it but the answers look very complicated.

Andy S

najaB · 9 Mar 2015

ash39 said:
Spirax valve. Seems most noticeable on electrics, and 67s as the op suggested.

Is this the same reason that 91's tick like crazy when they're at a stand?

ash39 · 9 Mar 2015

Have to confess I don't know a great deal about it, but I believe it's some kind of air release valve on the compressor(s)

Kneedown · 9 Mar 2015

I believe the purpose of a Spirax Valve is to expel the moisture that builds up in the (compressed) air system of a loco/unit.

HarleyDavidson · 9 Mar 2015

Exactly right.

When you compress air, it gets warm and the moisture that's in the air condenses, this used to be got rid of with glass blubs under the air tanks, nowadays compressors are often accompanied by air driers, which remove most of the moisture in the air and therefore reduces the need for the glass bulbs, but the air driers can't get rid of 100% of the moisture, so there will always be a need to have these Spirex valves to dump/eradicate the remnants of the condensate.

ExRes · 9 Mar 2015

I always thought that the annoying ticking noise was a 67 under full power

HarleyDavidson · 9 Mar 2015

Ooo, that's harsh!

a1a.a1a · 10 Mar 2015

HarleyDavidson said:
Exactly right.

When you compress air, it gets warm and the moisture that's in the air condenses, this used to be got rid of with glass blubs under the air tanks, nowadays compressors are often accompanied by air driers, which remove most of the moisture in the air and therefore reduces the need for the glass bulbs, but the air driers can't get rid of 100% of the moisture, so there will always be a need to have these Spirex valves to dump/eradicate the remnants of the condensate.

Thanks for the explanation, can anyone similarly explain how it works?
I guess moisture drains/trickles down into a sump, releasing a valve once enough weight has built up.... but that's just a guess?

DY444 · 10 Mar 2015

HarleyDavidson said:
Exactly right.

When you compress air, it gets warm and the moisture that's in the air condenses, ...

I think you've got slightly confused there, moisture condenses from air as it gets cooler

Water can form in the system as the pressure drops and the water vapour in the air condenses to liquid water. This can happen to an extent when running as there are pressure variations as air is used and replenished but is more pronounced when the loco/unit/vehicle has been left shut down for a while with pressurised air remaining (typically in the res tanks) and the pressure gradually falls due to leakage and the compressor can't run to replenish it.

HarleyDavidson · 10 Mar 2015

DY444 said:
I think you've got slightly confused there, moisture condenses from air as it gets cooler

Water can form in the system as the pressure drops and the water vapour in the air condenses to liquid water. This can happen to an extent when running as there are pressure variations as air is used and replenished but is more pronounced when the loco/unit/vehicle has been left shut down for a while with pressurised air remaining (typically in the res tanks) and the pressure gradually falls due to leakage and the compressor can't run to replenish it.

Yep, senior moment. If this is what getting older is all about then take me to the knackers yard now.

You're right of course, but we're still dealing with condensate, which has to be got rid of and that's what the valve does.

Mark62 · 10 Mar 2015

Good question ans I have wondered the same thing. The station pilot at newcastle Central is a 67 and it ticks away all day waiting patiently for some work

Peter Mugridge · 10 Mar 2015

Mark62 said:
Good question ans I have wondered the same thing. The station pilot at newcastle Central is a 67 and it ticks away all day waiting patiently for some work

That's not a pilot - that's one of the ECML Thunderbirds isn't it?

sprinterguy · 10 Mar 2015

Peter Mugridge said:
That's not a pilot - that's one of the ECML Thunderbirds isn't it?

Yes indeed - There's not much call for a station pilot shuffling parcels vans in and out of the bay platforms at Newcastle these days, or for any other activity for that matter.

Ash Bridge · 10 Mar 2015

sprinterguy said:
Yes indeed - There's not much call for a station pilot shuffling parcels vans in and out of the bay platforms at Newcastle these days, or for any other activity for that matter.

Used to be 03s at Newcastle & York was it not? Oops think I may be showing my age here :oops:

sprinterguy · 10 Mar 2015

Ash Bridge said:
Used to be 03s at Newcastle & York was it not? Oops think I may be showing my age here

Newcastle certainly had 03s.

kermit · 10 Mar 2015

If it's the same ticking we're talking about, the old class 304 AC electric units used to do it. A lot.

doningtonphil · 11 Mar 2015

The trap is a Spirax Sarco BRair or BRoil trap. Never quite figured out how they work. Something to do with a disc with a groove on it. Usually to drain the water out of the main reservoir

kermit · 12 Mar 2015

doningtonphil said:
The trap is a Spirax Sarco BRair or BRoil trap. Never quite figured out how they work. Something to do with a disc with a groove on it. Usually to drain the water out of the main reservoir

Everything you could ever want to know right here!

http://www2.spiraxsarco.com/pdfs/TI/p610_10.pdf

DownSouth · 12 Mar 2015

DY444 said:
I think you've got slightly confused there, moisture condenses from air as it gets cooler

Or when the pressure rises

DY444 said:
Water can form in the system as the pressure drops and the water vapour in the air condenses to liquid water.

No. I suggest you go to your nearest university library and ask for their simplest book on thermodynamics before trying this post again.

Or at least do a search on the internet for the phase diagram of water. It's easy to find.

kermit · 12 Mar 2015

All this condensation talk is very well, but have we identified the reason for ticking?

doningtonphil · 13 Mar 2015

kermit said:
Everything you could ever want to know right here!

http://www2.spiraxsarco.com/pdfs/TI/p610_10.pdf

Yeah, seen that. But how does it work? I know the more water there is, the faster it pops/ticks sometimes so fast it makes rude noises which is why some people refer to them as far valves. How does the disc with the groove in it let water out of the system but keep air in?

Jamesb1974 · 14 Mar 2015

kermit said:
If it's the same ticking we're talking about, the old class 304 AC electric units used to do it. A lot.

Do you mean this? (Fast forward to 2:24). I always thought that was part of the braking system. Air pump running??

https://www.youtube.com/watch?v=qYASA8-8FAI

scott118 · 14 Mar 2015

Jamesb1974 said:
Do you mean this? (Fast forward to 2:24). I always thought that was part of the braking system. Air pump running??

https://www.youtube.com/watch?v=qYASA8-8FAI

At 2.24, is that not just a clapped out compressor running, post brake application?

Why do class 67's tick?

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