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Max safe pressure set by D2

What is the maximum safe air pressure if I adjust by D2 regulator?
Larry
1996 U295 36'
Build # 4805
Actually we sold it but just like to lurk

Re: Max safe pressure set by D2

Reply #1 –
The upper limit is probably the certified safe working pressure of your air tanks...should be stamped on the tanks somewhere.  My D2 is set for 105-125.  Nothing has blown up (yet).  I have seen reference in various places to "150 psi being the maximum service system air pressure allowed by government regulations".
1993 U280 SE 40' WTBI, Build: 4359
C8.3 300hp, 6-Speed, Exhaust Brake
960 watts on the roof (6 x 160)
Sorento (or BOLT) on a Kar Kaddy SS
"Nature abhors a vacuum"

Re: Max safe pressure set by D2

Reply #2 –
Mine has been set for 95 to 115 when a new one was recently installed.  The truck guy said that with this setting the compressor is not working as hard, and there is less pressure on the systems.
Mike Brady
'97 U320 SE. #5137
'13 Honda Fit
Willow Springs, MO

Re: Max safe pressure set by D2

Reply #3 –
Mine is currently set for 95-125 psi. I'd like the lower at 105 but don't need the upper higher. Is this possible. With the HWH correction on leaks at 105 or so the travel height alarm goes off until I get to 110. Any way to raise the lower without raising the upper?
Larry
1996 U295 36'
Build # 4805
Actually we sold it but just like to lurk

Re: Max safe pressure set by D2

Reply #4 –
 Larry , I have a feeling that is a set point and cannot be changed. Others will correct me if wrong.
JohnH
Coachless, now use aircraft. 2003 Ford Travelair TC280 class C. Super shape. Just for 1 yr .
1994 Ford E350 ClassC,total renovation inside and out. Now sold.
2000 U295  36' Cummins 350 c/w Banks Stinger, Resonator upgrade,Solar, LED lites.Residential fridge with slide out pantry. Build 5674. Sold
ex 92 GV 022C ored Cummins. Sold
ex 95 GV240 cat 3116. Sold
2017 Mini cooper s & 2016 land Rover LR2 HSE  LUX.
jhaygarth@aol.com    SKP #130098
treat everyone as you would like to be.

Re: Max safe pressure set by D2

Reply #5 –
The range between the low and the high is 20psi, and is not adjustable.
Don
Quote from: lgshoup –
Mine is currently set for 95-125 psi. I'd like the lower at 105 but don't need the upper higher. Is this possible. With the HWH correction on leaks at 105 or so the travel height alarm goes off until I get to 110. Any way to raise the lower without raising the upper?
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Don & Tys
1999 U270 3602 WTFE #5402
Xtreme Stage 1 w/Headlight, Step Conversion, etc.
2009 Honda Fit Sport with Navi
Freedom is NOT "just another word for nothing left to lose"... with apologies to Kris Kristofferson

Re: Max safe pressure set by D2

Reply #6 –
And I am told that the max air safety pressure is 145 ( from a very good source)
JohnH
Coachless, now use aircraft. 2003 Ford Travelair TC280 class C. Super shape. Just for 1 yr .
1994 Ford E350 ClassC,total renovation inside and out. Now sold.
2000 U295  36' Cummins 350 c/w Banks Stinger, Resonator upgrade,Solar, LED lites.Residential fridge with slide out pantry. Build 5674. Sold
ex 92 GV 022C ored Cummins. Sold
ex 95 GV240 cat 3116. Sold
2017 Mini cooper s & 2016 land Rover LR2 HSE  LUX.
jhaygarth@aol.com    SKP #130098
treat everyone as you would like to be.

Re: Max safe pressure set by D2

Reply #7 –
I attended Bendix Air Brake School many years ago and asked what the rating was on the air tanks. The teacher said they were rated at 150psi with a safety factor of 5 meaning they would not rupture until 750psi but that would never happen because the compressor would blow the head off at 550psi. That is almost a direct quote. A Bendix D2 governor is surely adjustable but having installed many of them, most were set correctly at 120 psi shut off and would come on at 90 psi.

Re: Max safe pressure set by D2

Reply #8 –
 
Quote from: lgshoup –
.............Mine is currently set for 95-125 psi. I'd like the lower at 105 but don't need the upper higher. Is this possible.................
Larry,
You can't adjust just the "cut-in". 
I don't think that's a good idea anyway.  It is much safer to run at a higher overall pressure (more braking system safety margin), there is plenty of safe working margin to system design margins and narrowing the differential is bad for the compressor.  The compressor needs idle time to cool down between work sessions (typically at least 90% idle to 10% work).
 
The difference between "cut-in" and "cut out" is always non-adjustable, on either fixed or adjustable "D2" Governors.  Depending upon which D2 Governor you have installed, the difference may range from 15 psig to 25 psig, but the difference is never adjustable, only the "cut-in" setpoint (or the "cut-out", depending upon how you want to think of it.  When you adjust the D2, you are simultaneously "sliding" BOTH "cut-in" and "cut-out"  up in pressure or down in pressure.  We recently addressed this in another post:................SEE
 Air Hose Connection
 
There are adjustable and non-adjustable governors available.  NAPA, for instance, carries many:
    • New and Remanufactured, 
       
    • Standard and Hi Temp,
       
    • Hi/Lo fixed psig,
       
    • Adjustable psig
 
For example:
TWD BEN800361            105-130              (New)                                          $52.65
TWD BEN275200N          90-105                (New)                                          $49.50
TWD BEN284358N          105-125              High Temperature (New)              $56.25
TWD BENOR275491X      100-120              Standard Governor, (Remanufactured) Adjustable              $19.35

The Code of Federal Regulations specifies Air Braking Systems design, test and working pressures.  I'm not sure but I believe that RVIA uses the same 49CFR Standard.

See the 49CFR 571.121 Std.

Buses under 30,000 lbs GVWR may use 85 psig lower pressure D2's (mostly for air brake equipped school buses).  For safety, trucks (and air brake equipped commercial vehicles over 30,000 lbs GVWR) must use D2's that cut-in at 100 psig or higher.
Lower weight FT's might get away with lower cut-in set points (85 or 90 psig), I guess, but most FT systems should maintain approximately 100-125 psi at all times. I don't know why anyone would want to decrease their braking safety margins, reduce braking system response times and increase their run time on a compressor by decreasing the cut-in to cut-out differentials, but to each his own.  NOTE that the CFR indicates that even lighter vehicles become unsafe at anything below 85 psig.

The CFR stipulates that the air system must be sized and governed to provide at least two full air brake system applications at GVWR (including ABS, if so equipped, which uses a lot of air).  Under extreme circumstances with an 85 psig Governor, that gets you from 85 psig to 60 psig.  Then if an air system fails to maintain pressure, by 60 psi decreasing, the low air warning light, mechanical flag and/or buzzer must activate.
If the light or buzzer activates, get stopped ASAP! Between 20-45 psi, the "Parking or Emergency" spring brakes will apply and if you are moving, this could be a WAKE UP CALL if you are still on the highway!

Code of Federal Regulation NUMBERS  to know:
 
    • 500 psig Wet, Front and Rear Air Reservoirs design test pressure (at time of manufacture, reservoir must hold 500 psig design [hydraulic] pressure for no less than 10 minutes)
       
    • 300 psig air system components design pressure (200% of Safe Working pressure)
       
    • 250 psig compressor safety valve(s) relieve to protect compressor from over pressurization
       
    • 150 psig safety valve (wet tank safety valve relieves) = (100% of Safe Working pressure)
       
    • Somewhere between 100 & 130 psig Compressor "kick-out" (depends upon the D2 Governor)
       
    • Somewhere between 85 & 105 psig Compressor "kick-in" (depends upon the D2 Governor)
       
    • 85 psig Bus Warning (School and Commercial Carriers)
       
    • NOTE: at 84 psig decreasing, even light weight school buses are in danger
       
    • 60 psig Low air warning light, mechanical flag and/or buzzer
       
    • 45 psig Spring brakes apply (actually 20 to 45 psig by 49CFR)

Hope this helps,
Neal
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Neal (& Brenda) Pillsbury
'02 U320 SPEC, 4200, DGFE, Build #5984
'04 Gold Wing
'07 Featherlite 24'
'14 Jeep Grand Cherokee Summit
MC #14494
Exeter, NH & LaBelle FL
Quality makes the Heart Soar long after Price is Forgotten

Re: Max safe pressure set by D2

Reply #9 –
I like mine since fixed at 110-130.  Better brakes.  And you can fill the tires
"Riding and rejoicing"
Bob
1997 U320 40' Mid entry, build 5132,  wtbi ce27, 4th owner
2007 Solara convertible
2 prodeco tech outlaw ss electric bikes

1095 watts solar
08 Ls 460 and a sc430
2000 Ford F-250 superduty 4x4

Re: Max safe pressure set by D2

Reply #10 –
What Neal said ;D I guess I should have just said the difference between cut in and cut out was not adjustable. The ones I have bought (3 now...) were all 20psi between hi and low cut, since these were bought at different locations in ignorance of the different options list by Neal, I assume that 20psi is most likely what you will end up with if just go to the parts counter and ask for a Bendix governor as I did. It was only the last time I bought one that I was asked if I wanted a fixed or adjustable governor. All three were 100-120psi...
Don
Don
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Don & Tys
1999 U270 3602 WTFE #5402
Xtreme Stage 1 w/Headlight, Step Conversion, etc.
2009 Honda Fit Sport with Navi
Freedom is NOT "just another word for nothing left to lose"... with apologies to Kris Kristofferson

Re: Max safe pressure set by D2

Reply #11 –
Our dash gauges indicate 110-130. Seems to work well for us.
David and Carolyn Osborn
1995 U320C SE 40' Build 4726 Feb 1995
FMCA 147762
Motorcade 17186

Re: Max safe pressure set by D2

Reply #12 –
My regulator cuts out at 120 psi and I do not intend to change it.  Rather sure that is the original setting from the factory.  The brakes work fine, why increase the stress on old parts and risk a failure? The compressor has to work harder and longer for the higher pressure; burning a tiny bit more fuel. You could by raising the rear of the coach put a lot of extra pressure in the rear air springs.  I don't believe there is a pressure regulator for the rear that drops the pressure like the front air springs which is set at 50-60 lbs.  If there is a regulator for the rear I haven't found it.  From past experience I believe about 80-90 psi will fully inflate the rear air springs, depending on the weight with shorter coaches weighing less.  If I am wrong about this someone please post a correction.
Jerry Whiteaker former owner 96 U270  36' #4831 Austin,TX-Owner Mods LCD TV w/front cabinet rebuild - LCD TV bedroom - Dual Central AC, either can cool coach w 30 amp - Skylights at roof AC openings - Drop ceiling for ducting of AC - Shower skylight white gelcoat/wood/epoxy frame - Air Springs/Shocks replaced - 2014 CRV - 8K Home Solar - Chevy Volt

Re: Max safe pressure set by D2

Reply #13 –
All the vehicles in the fleets I managed were set at 120psi max.

Keith
Keith, Joyce & Smokey the Australian Cattle Dog
1995 U320 SE Extreme 40' WTBI Build # 4780, with a Honda CR-V hopefully still following behind.
Motorcade # 17030
FMCA # F422159
 

Re: Max safe pressure set by D2

Reply #14 –
I paid attention today because off this thread.  After initial warmup I can drive in traffic with no retarder at 120-130.  Requires a hard physical push for max effect unless recently hot.

System designed for the retarder obviously.

Without it the braking would be increased from the pedal I bet.

I like the exercise without the retarder.  Lever and off button are exactly to my left and can be turned on quickly if needed.

Just playing.....
"Riding and rejoicing"
Bob
1997 U320 40' Mid entry, build 5132,  wtbi ce27, 4th owner
2007 Solara convertible
2 prodeco tech outlaw ss electric bikes

1095 watts solar
08 Ls 460 and a sc430
2000 Ford F-250 superduty 4x4