View Single Post
Daveinclarkston Daveinclarkston is offline
Registered User
Join Date: Oct 2005
Location: Howell, MI
Posts: 60
Hi Wayne,

The new Meritor WABCO hyd commercial brake system we released a few years ago includes two accumulators and during the development proceess I recieved a little bit of education from the engineers. The accumulators we use are a mixed gas (Nitrogen is the main gas and I can't remember the second off the top of my head) which slows the migration of nitrogen through the membrane. With the mixed gas the life of the accumulator has a normal life of 12 years and was only about 4 years with just nitrogen. The problem was not with failure of the membrane but the loss of pressure due to the gas migrating through the membrane, which is a normal process.

One thing we did review during the devleopment process was should we make the accumulators serviceable. We elected not to do so due to additional up front costs and additional lenght of the accumulator. Yours look sealed but you may want to check to see if they can be refilled. The other thing that leads to a more rapid loss of nitrogen is high heat useage. We estimated that vehicles opperated in Arizona would see shorter accumulator life than those in Alaska for example.

Also, in an attempt to find the most cost effective accumulator I did find that there are only two manufactures of nitrogen accumulators in the world and both are based in Germany. Ours are from Freudenberg. I sent you a pm with the maufacturing process of an accumulator. Ours have a 75 bar pre charge when new. Not sure about the Benz have vs the Porsche but this may limit what you can do or limit the usage as the gas is lost over time.

9K is a big hit! Sorry to tell you that I think we were paying somewhere in the $30 range each if my memory is correct. I have also sent you another PM with information on storing accumulators. Per the information I sent our manufacture states that while no loss of gas is expected when empty they do not reccomend storing accumulators for more than five years.

By the way did Dirk send you the pacakge with the test pin out box? If not I'll send him a note as I know he gets busy.
87 911 coupe
92 NSX (sold to be replaced by another 911)
09 Escape 4WD
Old 12-02-2007, 07:53 AM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #13 (permalink)