It is currently Thu Apr 18, 2019 12:39 pm

All times are UTC - 5 hours [ DST ]




Post new topic Reply to topic  [ 6 posts ] 
Author Message
 Post subject: 26L won't maintain
PostPosted: Fri Apr 12, 2019 6:01 pm 

Joined: Tue Jun 14, 2016 6:14 am
Posts: 22
Hello all,

I am having a issue with 26L not maintaining a brake reduction. Just replaced the automatic brake valve and the P-2-a. After making a reduction it will hold and then the automatic brake starts venting off slowly. The locomotive is the problem. It will maintain in passenger though. In freight no luck. I have crawled over looking for a air leak. Any Ideas?

Thanks in Advance


Offline
 Profile  
 
 Post subject: Re: 26L won't maintain
PostPosted: Fri Apr 12, 2019 7:08 pm 
User avatar

Joined: Tue Feb 20, 2018 7:08 pm
Posts: 64
Location: Alberta, Canada
I was told by an old head engineer that a leaky gasket/o-ring on the line to the equalizing reservoir gauge is a likely cause of this problem.

Your problem is a uncommon but not rare occurrence on our (CN's) locomotives with 26 and 30 brake systems. Today we just flip it over to Passenger and keep going, I have never attempted a repair myself.

_________________
Greetings from Alberta
-an Articulate Malcontent


Offline
 Profile  
 
 Post subject: Re: 26L won't maintain
PostPosted: Sat Apr 13, 2019 3:05 pm 

Joined: Sun Aug 22, 2004 11:06 am
Posts: 494
Location: NE PA
I will second the leak in the equalizing reservoir piping, O rings in Salem gauge test ports, Salem gauge mounting plate are not uncommon along with piping leaks. A loosely rolled newspaper rubbed against the piping with the engine shutdown may help amplify the leak.
Mike Tillger


Offline
 Profile  
 
 Post subject: Re: 26L won't maintain
PostPosted: Sun Apr 14, 2019 3:47 pm 

Joined: Sun Aug 22, 2004 10:18 pm
Posts: 90
Location: Philadelphia, PA
Take a close look and make sure equalizing reservoir pressure is not actually rising. With the ABV set to freight position about a two pound rise in equalizing res pressure is enough to get the 26F to go to release. When the ABV is in passenger and the F control portion set up to graduated the issue will take more time to manifest itself.

I’m not close to my schematics but it’s also helpful to know how the unit is piped as related to J Relay type.

EBL


Offline
 Profile  
 
 Post subject: Re: 26L won't maintain
PostPosted: Mon Apr 15, 2019 11:11 am 

Joined: Fri Nov 16, 2007 10:21 pm
Posts: 100
I'm assuming that what you are experiencing is that with the independent brake in release, you take a set with the automatic, the brake cylinder pressure comes up as normal, and then slowly bleeds off? It's also important to note whether the brake valve bleeds down with the brake stand cut out.

When we encounter problems of that nature, it almost always ends up being either a small plumbing leak, or a bad check valve. Air leaks can be hard to diagnose, because it doesn't take a very large leak to present a problem, and the leak may only be present for a few seconds. Lots of soap suds and eyes on the brake lines while someone else works the controls.

My vehicle mechanics have a smoke machine they use to find vacuum leaks on automobiles. I've contemplated using this for diagnosing air leaks on brake systems, but have not figured out how to go about that yet.

Eric


Offline
 Profile  
 
 Post subject: Re: 26L won't maintain
PostPosted: Wed Apr 17, 2019 3:52 pm 

Joined: Tue Jun 14, 2016 6:14 am
Posts: 22
Thanks For the help. It was the gage orings. Works like a charm now.


Offline
 Profile  
 
Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 6 posts ] 

All times are UTC - 5 hours [ DST ]


 Who is online

Users browsing this forum: 6-18003, Crescent-Zephyr, JimBoylan and 40 guests


You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot post attachments in this forum

Search for:
Jump to: