Single check valve

[Robo McDuff]

I redid the Airpack and brakes. The front glad-hands are broken beyond repair, so I am replacing them with European glad-hands and now I am trying to connect metric glad-hand with the old air lines using US threaded bolts. Had to use an angle grinder to get the connector through the bumper off. Then I noticed a strange construction on the left side just behind the bumper. I thought it was just something somebody put inbetween to bridge a gap in the lines, but when opening it, found out it is a valve of some kind. Checked it: it is the "single check valve".

Now my question is, if I turn that valve around, will it block the air from going from the air tanks to the new glad-hand? Would be usefull, because I am still figuring out how to connect the new and the old stuff, and if I can block this line simply for the moment, it saves me a lot of time trying to get the stuff together.

Actually, I don't need the front glad-hands at all, just need to block the lines so I can get the truck driving and braking.

And now we are at it, can somebody tell me why the air system has connectors with two different thread formats? They just get a sadistic pleasure from it making things unnecessary difficult?

 

[Scrounger]

The front glad hands as you are probably aware of are for when the vehicle is being towed. The emergency (red glad hand) side supplies the vehicles air tank(s) from the tow vehicle so the towed vehicles brakes will function while being towed. The check valve is to prevent the loss of air if the airline were to become disconnected while towing. It also prevents air loss if someone neglects to close the valve going to the glad hand. It is amazing how many youngsters in uniform don’t notice things like that. Sarcasm button off.

If you don’t plan on towing the vehicle, just capping the line will get the vehicle roadworthy.

I’ll give a stab for the two thread formats. The air lines from the air pack, compressor, fitting underneath, etc. use the standard fine thread format and usually use ferrules and compression fittings. For the fittings at the glad hands, and the usually steel valves for them, use the National Pipe tapered thread format. The only thing they need is pipe dope or Teflon tape when connecting them. Why they use the tapered thread is anyone guess. Maybe because steel was cheaper and stronger for larger fittings.

 

[Robo McDuff]

So how it was installed would stop air from getting to the glad-hand?

I would love to cap them, but no fitting caps, so the single check valve would do nicely.

My problem is that the airpack fittings use one thread, then in some places you need to put a connector between the airpack port (larger, course thread) and the output line toward whatever: mostly smaller size AND fine thread. ff course nobody here as anything coming close to that kind of madness.