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  • #46
    Well I had a look at my engine this morning and it is as I suspected, the air dryer is plumbed all wrong and I suppose yours is too. The line from the discharge of the compressor is supposed to be all downhill and is supposed to be copper so it can give up its heat, and also meet a minimum length but most manufacturers don't bother with that and in this case it goes down below the motor, crosses under as cloth covered wire braided hose (insulating rather than heat dissipating) and finally it makes the connection to the dryer inlet through an elbow which is another no-no. What this means is that the water the compressor puts out will accumulate in this trap and then "slug" the dryer all at once when enough comes along and pass right through into the system. Also since the air coming in has not had a chance to cool that well due to the short length of insulating hose, it will not give up as much water to the dryer as it could, and more will pass into the tanks. And finally the "system purge" concept, which was relatively new at the time, means that the system air is used to purge the dessicant and if it is being used in the truck at the same time, the purge time is cut short, further saturating the dessicant...if all systems are working properly the first thing I would do would be to see if I could retrofit a good old AD-9 to the system.

    If the problem is related to shore air, as you said discontinuing that might solve the problem but a Kussmaul compressor is not going to help unless it goes into the air system before the dryer and even then, when the dryer becomes saturated it is no longer going to do any good. This could be done with shore air as well though.

    One thing I have considered, assuming you have a station compressor that goes higher than the cut-out pressure of your engine, is to plumb a relay valve to the inlet port, working off the governor, so that air comes into the system and then gets cut off and gives the dryer a chance to purge, same as when using the compressor. However I haven't actually done it because the only apparatus I use shore air on is from my shop air which is very dry already and needs no further treatment.

    Even if freezing isn't a problem, it is good to keep all moisture out of the system, because any condensation ends up washing the grease out of the system valves, and that is what keeps them working. Once the grease is gone they fail.

    Of course the best solution to this problem is to put into the vehicle spec that the manufacturer will plumb the air dryer system not deviating from the manufacturer's specs and not use a system purge dryer.

    Birken

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    • #47
      Or you can do (gulp)what those of us that HAVE to go do.Put and maintain a Alcohol evaporator in the system.Every time the govenor cycles it puts a trace "shot"of alcohol in the system.No freeze ups and no failures.Quite embarrassing to be sitting beside the road with a broken rig on the hook and no air pressure.I buy brake line antifreeze by the case in Oct and we use it all winter long.Now if I could only get my electro-hydraulic controls to be as dependable. T.C.

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      • #48
        Not to cause a battle or anything but alcohol evaporators have the same effect as water in the system if not more so, the alcohol is a solvent that strips the grease from valves. IF the air dryer is working properly, there should be no water to freeze...but you also have to put a rig out of service for a failed valve too, not just frozen water.

        Birken

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        • #49
          After being in the fd for 32 yrs. and living in Vt. for 50 plus yrs, we used to drain our pumps, then we decided to try them wet at 55 degrees in station we never had a problem except for the primer once in a while.

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          • #50
            Birken,Don't know what to tell ya. I've been using alky in my systems for over twenty years and I've yet to replace a valve for anything outside of old age.As I mentioned earlier, my equipment HAS to go and like Fire apparatus is required to be ready 24/7/365. A LOT of companies in my area run alcohol evaporators and I don't see a big rush on at the parts stores for air brake parts. I DO see a lot of frozen systems on rigs that DON'T use them.But you're CA and this is Maine,the weather factors ARE different.And I'm not getting into the variables,I'm not a weather scientist.I value your opinions but I know what works for me:ANTIFREEZE. Matter of fact I think I'm gonig to find MY antifreeze right now,Hehe T.C.

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            • #51
              I know, I know...but what constitutes "old age?" A valve should last the lifetime of the truck if the air is properly treated. My information about water, alcohol, valves, and the grease within is from Paul Jones, the big kahuna field service rep with Bendix in the West.

              Anyway, on almost every fire truck I see, the air dryer is plumbed totally improperly. There should be a few feet of stainless steel/Teflon hose and the rest should be copper, sloping downhill to the dryer, entering the dryer through a straight connection, not an elbow. And of course the dryer itself has to be operating within its own limits. Do any of your trucks meet that? I don't think any of mine do except maybe one old Ford.

              If there isn't water in the system, it can't freeze

              Birken

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              • #52
                Birken,

                To answer your 1871 questions: Yes and Yes.

                The coolant line is the least of our problems on that chassis. We have had a number of fairly serious electrical problems, currently are having suspension problems, and have terrible factory support from HME!

                Yes, our drier is plumbed like yours - incorrectly.

                I actually disconnected the Kussmaul recovery pump on board because of condensation problems in poorly run air lines. The thing cycles 2-3 times a minute and drove everybody crazy. It was replaced with a shore line. The shore line is VERY dry air (2 driers in close proximity), so I doubt the problem originates there, although at this point I would not be surprised.

                This truck has an ISC in it - I would give anything to change the "C" to even an "L", preferably an "X" :-D

                Birken, PM me some contact info, I'd like to discuss some problems I've had with this truck with you.

                Thanks,
                Jon

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                • #53
                  My experience here in the mid Atlantic area is been to leave the pumps wet. Once thing that I was taught when I was a newbie pump operator has worked very well in the past when it gets really cold. That is to enclose the bottom of the rig with salvage covers, to help keep the cold air out from under the rig and help hold some engine heat in. Don't put a cover over the exhaust area, that would melt the salvage cover. Drape the cover over the front bumper, tailboard, running boards, etc. I then use adapters and such to weigh the cover down to hold it in place. I only do this for a working fire when it's below 25 deg or something of that nature. One alarm in the past when it was 10 or 15 deg, had no problems operating for hours at a major building fire. Lots of other departments had freezing issues, the salvage cover trick worked. We don't have pump heaters. Anybody else ever use this method?

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                  • #54
                    Birken,What's the "lifetime" of a truck? Some of my stuff is close to thirty years old and has the original valves.The two I replaced I damaged thru ignorance(not alcohol related).All of what you say makes sense,by the way what's a dryer?(hehe)No,probably 80% of the rigs on the road are plumbed wrong. T.C.

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                    • #55
                      Originally posted by chiefeng7
                      Birken, PM me some contact info
                      I tried PM and to email you and the board won't let me do either...my daytime number is 530-432-2630, I work monday-wednesday every week.

                      Birken

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                      • #56
                        What I dont understand is why do we empty the water in our grass truck in the winter. Yeah there arn't too many grass fires with snow on the ground, BUT he have had 2 calls requiring 17 to go out, and have had to wait to fill up the tank. Makes NO sense to me.

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                        • #57
                          I can't say specifically as it relates to your truck hfd2049, but most brush trucks lack the ability to circulate water in large volume, they have smaller tanks which are more exposed to the elements and therfore less heat stored and a faster heat loss rate when you go out, and at least around here they are often used on down wires/limbs call which require them to sit outside for long periods of time waiting for the power co to show up. All this means they are more likely freeze up compaired to the big trucks.
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