Broken air valve - what is it?

Tubing O.D. and NPT size are two different things.

1/4" NPT is about 1/2" O.D. actually.
3/8" O.D. nylon tubing is about 1/4" I.D.

The one pictured is what you want.

You could just zip tie the valve to the bracket for now.

 

valve must be secured with two 8 mm ore 11/32" bolts. it is the law

 

That is a none compounding Quick release. It is installed on you spring brakes so if you put the service brakes on, with the spring brakes applied the air will be directed to the spring brake releasing the pressure on them and also applying the service brake. It is on there so you do not strip off the "S" cam splines, or damage the slack adjuster.

 

Yeah, I understand about preventing double pressuring like stping + service brake forces, but seems to me it is kind of paranoia, becouse all brake things are designed with x4 stress, so brake spring force is equal 100 PSI pressure in service brake chamber, so together - about 200 PSI... no. not enought to damage s cam ore bracke shoes

 

I'm not saying I know the law, but where does it say air valves must be bolted to bracket or frame? There are inline valves like pressure protection with no provisions for bolts. Just curious.
I know the lines can't rub anything.

 

In Europe we use this kind of fittings


So if if I swap US valve with European one I use European fittings ore adapters (usually M22x1.5 to 1/4")

 

The spring brakes are usually fully released by 60 lbs. And they did design the valve to stop a problem with `S`cams, the slacks, the brakes shoes and the `S`cam rollers all had many failure problems before this valve was installed. There is still incidents where problems can be related to brake application pressure.