I’ve been working at my current job since January, i coupled up when i was given a motor and haven’t dropped the trailer since! in my last job we could do 2 or 3 trailer changes a day, often picking up ‘stand’ trailers from customers yards which meant dropping the one you’d brought in, picking up and moving the loaded trailer, then dropping that and coupling up to the first trailer to put it where you fetched the loaded one from. due to all the shunting about some drivers would put airlines on to move them, others would just push the shunt button, i hear one of the drivers on my old firm recently dropped a loaded trailer on it’s knees when he didn’t couple up fully. We had some trailers with the automatic red button, that pops out when the red airline is removed, it doesn’t ‘pop’ back in again when you put the red line on!
it all comes clear then it gets confusing again reading from the posts
so to be safe when you go to couple the red button on the trailer should be out (brakes on)
if brakes on there is no danger of trailer moving and presume after u connect up airlines u dont have to push the red button it as it automatically does it when u pull away
no you still have to push the red button in manually to move off, but with an automatic one the button will pop straight back out if the red airline isn’t on!
nedflanders:
:lol: it all comes clear then it gets confusing again reading from the posts
so to be safe when you go to couple the red button on the trailer should be out (brakes on)
if brakes on there is no danger of trailer moving and presume after u connect up airlines u dont have to push the red button it as it automatically does it when u pull away
No mate, you’d have to push the red button after connecting up before the trailer brakes would release.
nedflanders:
if brakes on there is no danger of trailer moving and presume after u connect up airlines u dont have to push the red button it as it automatically does it when u pull away
No - the trailer brake will never cancel as you move away. If you set it, you have to clear it to move away.
There’s two problems with button-operated trailer brakes:* is the brake ‘on’ when the button is pulled out or pushed in?
- does the trailer brake set automatically when the red line is disconnected and/or air tanks in the trailer run low?
So far as I can make out, usually you pull the button to set the trailer brake and push it in to clear it.
Most trailers do not automatically set the trailer brake, but some trailer brakes do set automatically when the red line is disconnected or when the air tanks in the trailer run down.
All this worry about brakes and lines takes me back to when we changed over from having taps on the airlines to having the valve in the coupling, i remember taking a trailer out that had already been coupled for me, i know i should have checked myself, but for some reason the chap who’d coupled it up for me had turned on the valve on the red line, but not on the blue and yellow, (primary and secondary brakes) i left the yard and as i dropped down into the nearby village had a very scary few moments as i only had brakes on the unit and only just made it round the corner, going a lot faster than i would have thought possible!
ashbyspannerman:
All this worry about brakes and lines takes me back to when we changed over from having taps on the airlines to having the valve in the coupling, i remember taking a trailer out that had already been coupled for me, i know i should have checked myself, but for some reason the chap who’d coupled it up for me had turned on the valve on the red line, but not on the blue and yellow, (primary and secondary brakes) i left the yard and as i dropped down into the nearby village had a very scary few moments as i only had brakes on the unit and only just made it round the corner, going a lot faster than i would have thought possible!
Same thing happened me and I struggled to hold off a jacknife as I slid into Leicecter Forest East services on a wet Monday.
Equitran:
Same thing happened me and I struggled to hold off a jacknife as I slid into Leicecter Forest East services on a wet Monday.
we weren’t far apart then, i did it near Melton Mowbray!!
Lucy:
And no, I couldn’t care less how many shunters I upset,
That’s a perk of the job isn’t it? 
On a serious note for any newbies reading, there are sites where the shunters don’t like you setting the park brake and will tell you to leave it. Ignore them. And remember there are still a few old trailers about that use a ratchet and cable set up and you can pretty much guarantee maintenance has been sporadic if any. Take a little extra care with them as the brakes don’t hold as well .
waynedl:
limeyphil:
Big Joe:
ncooper:
Scania and Volvo, for example, have no air pressure in the yellow line when the hand brake is on,
therefore connecting the yellow line has no effect on the trailer brakes.
well you learn new something everyday
if connecting the yellow airline has no effect on the brakes. then how the hell do the brakes work?
Off the foot brake (aka the service brake), maybe that’s why it’s known as a service line?
He only said with the handbrake
The foot brake is often referred to as the foot valve, it opens an air valve when the brake pedal is applied.
At the end of the day if you didn’t have to use a trailer brake then it wouldn’t have one on. If anything were to go wrong the first thing they would ask…was the trailer brake on?
SB
ncooper:
If a trailer is fitted with spring brakes it will NOT move if there is no air in it.
The air supplied through the red air line fills the trailer air tank and the suspension
if it is air.
This air is used to hold the spring brakes off, the trailer park brake button works by
releasing the air from the brake chambers, allowing the springs to apply the brakes.The shunt button works by filling the brake chambers with air, thus forcing the springs
off and releasing the brakes.If your trailers’ brakes stop working when the air is down, they are either NOT fitted with spring brakes,
highly unlikely, I would have thought, or the springs are weak or broken.Trailers used to have a ratchet tensioned cable handbrake, normally acting on one axle, as you say,
but in those days they didn’t have spring brakes.
The brakes were applied by air pressure, so the trailer would roll when the air was gone.Regards,
Nick
^this^
I’m dumbfounded by some of the comments regarding something as simple as hooking up to a trailer 
Are people really that stupid 
It is a simple process, even split coupling, a lorry and trailer are not transformers that will turn into a deadly machine if you blink for a moment Yes, people get hurt once in a while during the coupling/uncoupling process, but that is usually because they have done something wrong, or because they are an idiot and try as hard as you like, but you cannot fix stupid
newmercman:
…a lorry and trailer are not transformers that will turn into a deadly machine if you blink for a moment…
I’m not convinced.
Hells bells guys, its obvious listening to this some of you have no idea how the brake system on your vehicles work, which to be honest is frightening. In basic terms the foot pedal or Service brake sends air through the Yellow line to the trailer brakes during normal driving, I’m sure everyone understands that. The handbrake is not just a park brake but also a Secondary brake, pull it slowly on and air will again travel through the Yellow line to trailer brakes, in other words a second braking system which is hand operated incase of failure of the foot brake, it became law back in the Sixties that all vehicles had to have a secondary brake system.
When units had the old ratchet mechanical handbrake or similar a separate hand operated air brake was fitted, usually around the left side of the steering wheel, this became known as the ‘Dead Man’ and a third Blue air line was needed to allow air from this to pass to the trailer brakes, the Three line system. When we changed back to the Two line system as used by the continent the secondary brake was incorporated into the hand brake lever. Once the lever is pulled over the notch the hand brake is applied to the unit, air does not continue to the trailer brakes so putting the handbrake on makes no difference to the Yellow line, hence the yellow line does not blow off like the Red when uncoupling the connection.
The Red line as rightly said continually feeds air to the trailer, it needs to do that to keep the brakes released during driving. When the Red line is disconnected you get a small blow off but the self sealing valves in the connection stop any more air escaping. The trailer brakes are held on with air pressure held in the trailer air tank and not spring brake (mechanical pressure) . If this air drains off (mostly overnight) the Spring brake section in the brake chambers overcomes air pressure that is left in the system and applys the brakes mechanically. Put your Red line back on and air pressure releases them again.
Obviously there are various valves in use to do these operations in the correct way and quickly but that is basically how the system works. Now hands up who didn’t know about the Secondary brake system, it could save your life if your foot valve failed so find out about it on your vehicle. Some vehicles may differ slightly in this system depending if Spring brakes are fitted to the front axle and not just the drive and trailer, manufacturers don’t all have the same way of braking on vehicles but they must all have a Secondary system. Hope this helped. Franky.
i once had to ease the handbrake on,when my footbrake failed whilst going down hill.this was in a 7.5 about 23 years ago 
Frankydobo thank you for explaining the secondary brake system. I was somewhat amazed reading the thread how many drivers, including some old hands, seemed completely unaware of it. You explained it well and saved me a lot of typing. 
One wonders how many, over many years, totally unnecessary accidents have occurred when the service (foot) brake valve has failed but the driver has been in total ignorance of the secondary braking system available to him.
newmercman:
ncooper:
If a trailer is fitted with spring brakes it will NOT move if there is no air in it.
The air supplied through the red air line fills the trailer air tank and the suspension
if it is air.
This air is used to hold the spring brakes off, the trailer park brake button works by
releasing the air from the brake chambers, allowing the springs to apply the brakes.The shunt button works by filling the brake chambers with air, thus forcing the springs
off and releasing the brakes.If your trailers’ brakes stop working when the air is down, they are either NOT fitted with spring brakes,
highly unlikely, I would have thought, or the springs are weak or broken.Trailers used to have a ratchet tensioned cable handbrake, normally acting on one axle, as you say,
but in those days they didn’t have spring brakes.
The brakes were applied by air pressure, so the trailer would roll when the air was gone.Regards,
Nick^this^
I’m dumbfounded by some of the comments regarding something as simple as hooking up to a trailer
Who are you to sit there and make cocky comments about people asking questions with regards to an area of the job they are unsure of?
Your just a driver like everyone else, so remember your ■■■■■■■ place… ■■■■■
Saaamon:
newmercman:
ncooper:
If a trailer is fitted with spring brakes it will NOT move if there is no air in it.
The air supplied through the red air line fills the trailer air tank and the suspension
if it is air.
This air is used to hold the spring brakes off, the trailer park brake button works by
releasing the air from the brake chambers, allowing the springs to apply the brakes.The shunt button works by filling the brake chambers with air, thus forcing the springs
off and releasing the brakes.If your trailers’ brakes stop working when the air is down, they are either NOT fitted with spring brakes,
highly unlikely, I would have thought, or the springs are weak or broken.Trailers used to have a ratchet tensioned cable handbrake, normally acting on one axle, as you say,
but in those days they didn’t have spring brakes.
The brakes were applied by air pressure, so the trailer would roll when the air was gone.Regards,
Nick^this^
I’m dumbfounded by some of the comments regarding something as simple as hooking up to a trailer
Who are you to sit there and make cocky comments about people asking questions with regards to an area of the job they are unsure of?
Your just a driver like everyone else, so remember your [zb] place… [zb].
Your use of the [zb] is not allowed as you are using it to call me rude words, that is not how we work here, so behave yourself or the mods will be removing your personal attack, no sorry, your unprovoked personal attack
Who am I? Someone who knows how the [zb] brake system on my lorry works, that’s who I am mate 
Now to answer the question you should’ve asked as you seem so upset by my response. I am not having a go at anyone for not knowing how the systems work, what I do find riduculous is that people consider everything to be so dangerous. The post asked isn’t this how people get hurt? Well no it isn’t, you could park a million and one trailers with no parking brake applied and not one single person will get hurt
All this danger around every corner nonsense is just that, nonsense and if you don’t like my opinions then you have two options, one is the foe button, add my name to it and you’ll never see my posts again or two, ■■■■ off and grow a pair you purple headed custard spitter 
And you could back under your first trailer and it could bite ya on the erse Mark? I appreciate what your saying but there are newbies reading and to them it’s all new and unfortunately the training after they’ve gained their licence leaves a lot to be desired. No harm in frightening them a bit at this stage,eh? 
i must admit i did`nt have a clue how the brake system works…how would i at no time during my training,or since,has anybody explained the mechanics of a modern braking system.
when my brakes failed,i went for the handbrake through instinct…it was the only option available to me,either that or jump 