1. #1
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    Default pressure governors

    Can someone help or point me in the right direction for more knowledge on pressure governors, class 1. like the drop to idle speed if you lose intake pressure , I kinda got an understanding on it but want more. Like our is rated at 30psi min on the discharge side or it will go to idle. I'm a little confused on that and need more.
    I understand if I go to RPM mode while changing over to hydrant pressure it wil not lose pressure on the discharge side, if I leave it in PSI mode it will kick it down to idle, even after bleeding all the air out. After that I go back to PSI mode or governor and everything goes back to normal. You just have to be careful and watch your pressure while in RPM mode for the guys while switching over to hydrant pressure.
    I've watched the movie, took the truck out and pump it all different ways. Feel very comfortable but want to be able to explain it better

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    The simplest way to explain the theory is that it's designed to prevent too much discharge pressure, as well as protecting the pump itself.

    If you put the system in PSI/Pressure mode, it will detect the incoming and outgoing pressure and adjust engine/pump speed accordingly. So if it all of a sudden detects a surge of incoming pressure, ala switching from static tank water to a dynamic source like a hydrant or feed from another truck, it will quickly drop the engine RPM, possibly all the way down to idle depending on how many discharges you have going and what the speed of the engine/pump already is. This is designed to prevent too much pressure from making its way to the discharges. Remember, any pressure going into the pump gets multiplied by x amount as it leaves the pump. When you have a static source like tank water, the pump is doing all the work. Generally, while at idle the pump output will be around 50 PSI with a static source. But if you all of a sudden introduce 50 PSI into the pump intake, you'll now be putting out at least 100 PSI. Obviously the governor has almost no impact when the truck is already at idle, because there is really nothing it can do to further decrease the pressure, short of trying to dump that excess pressure onto the ground via a relief valve.

    If you put the system in RPM/Throttle mode, you are stopping the system from monitoring the incoming and outgoing pressure altogether. The only thing it is concerned about at this point is the speed of the engine/pump just as if you were operating an older style vernier throttle. The problem with this mode is that if you're not monitoring and adjusting engine/pump speed yourself, and you open a pressurized intake, the discharge pressure is going to spike. If you had the engine/pump speed set to 1200 RPM to get 100 PSI out of a static source like tank water, then you open an intake with 80 PSI on it, you'll now be putting out at least 180 PSI unchecked for each discharge.

    Also, as I said, the system is designed to protect the pump. It does this by dropping the engine/pump speed to idle if it detects x amount of seconds without any incoming/outgoing pressure. So if you were to walk away from the pump panel and the truck ran out of tank water or you lost your supply line, the pump won't run dry at an elevated RPM for very long.

    In short, there is very little reason to pump in RPM/Throttle mode, as you defeat the entire purpose of the system.

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    I didn't get to absorb all your info yet, I need to read it a couple more times.
    Question is, then why is it that everytime we start to take in hydrant water while in PSI mode it does all funky read outs, like operator and low pressure and eventually goes to idle? This happens with all our engines.
    Even if I do the right way, bleed off air in 5", open stortz real slow it still does it in PSI mode, why? Even in the movie that comes with it expresses to go to RPM mode while switching over to hydrant and then back to PSI(pressure) mode afterwards. And also it says to be in RPM mode for relay.

    Thanks so far, I want to be 100% comfortable with this system

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    I forgot to mention one other feature when it's in PSI/Pressure mode. It will automatically adjust engine/pump speed to compensate for any pressure fluctuation either on the intake or discharge sides of the pump.

    Example 1: If you set the pump at 120 PSI with one discharge open, then you open a second discharge, the governor will increase the engine/pump speed to keep the discharge pressure at 120 PSI. In contrast, if you were to close a discharge, the governor will decrease the engine/pump speed so it again maintains 120 PSI. Had you been pumping in RPM/Throttle mode when opening the additional discharge, the discharge PSI would've decreased and obviously reduced the effective PSI/GPM on each discharge. Had you closed a discharge in RPM/Throttle mode without decreasing the throttle, there would be a surge in PSI on the already open discharges. Obviously if that PSI is high enough, you can get someone hurt.

    Example 2: If your incoming pressure fluctuates, the governor will attempt to compensate. Let's say you have 50 PSI incoming from another truck with your pump discharge pressure set to 120 PSI. If the other truck were to suddenly increase its pressure to 80 PSI, your pump governor would decrease its engine/pump speed accordingly to compensate. Likewise if the incoming pressure were to drop to 20 PSI, your governor would increase engine/pump speed in an attempt to maintain the 120 PSI discharge pressure.

    Confused yet?

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    Quote Originally Posted by mook13
    Question is, then why is it that everytime we start to take in hydrant water while in PSI mode it does all funky read outs, like operator and low pressure and eventually goes to idle? This happens with all our engines.
    Even if I do the right way, bleed off air in 5", open stortz real slow it still does it in PSI mode, why?
    I suspect it drops down to idle because there is more than enough incoming pressure when you open the 5" that you don't need the pump to be boosting it much. It would depend on how many and what size discharges you had open at the time, what discharge PSI you had the pump set at, and also what your incoming pressure was.

    Quote Originally Posted by mook13
    Even in the movie that comes with it expresses to go to RPM mode while switching over to hydrant and then back to PSI(pressure) mode afterwards. And also it says to be in RPM mode for relay.
    Really? Hmm, I wasn't aware it said that. Although I have to admit, I've never used the Class 1 system. My knowledge is from using the Pierce/DDEC system, but they all operate on the same principles. Maybe someone else can explain why Class 1 would recommend switching to RPM mode in these situations. I do not recall hearing that with the Pierce/DDEC system.

    Also, when they say to switch to RPM mode for relay pumping, are they only talking about the inline pumpers as opposed to the last pumper that is actually flowing handlines? I couldn't imagine any reason why you would purposely defeat the safety features on the last pumper that has guys on the lines.
    Last edited by Chauffer6; 09-28-2006 at 03:04 PM.

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    I'm a firefighter in Houston, TX and we just got some Ferrara pumpers last year and they have the Class 1 pressure governor. I was the assigned chauffer on our engine for 1 year before being promoted and we don't use the rpm mode unless we're drafting, which is very rare for us. Like one of the other guys was saying, your pump and/or firefighters aren't protected in the rpm mode. I trained the crews on the new engines and don't recall anything that says you have to be in rpm mode on tank water and then switch to pressure mode once you get a hydrant. You should just go straight to pressure mode after you put it in pump gear. The problem we're coming across is that the governor seems to be overcompensating when going from tank water to hydrant pressure. I called Class1 and the guy I spoke with was very polite and gave me some things to look in to. Use the link that was provided in another response and try that. Good luck. Be safe.

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    again, I totally understand they are not protected in RPM mode. But it does over compensate when switching from tank to hydrant water. There is a training movie that came with out E2 and then about 2 years later when we got our E4 with the automatic governor, it came with the same training tape. Why does it over compensate and then go to idle?


    Quote Originally Posted by johnkerr
    I'm a firefighter in Houston, TX and we just got some Ferrara pumpers last year and they have the Class 1 pressure governor. I was the assigned chauffer on our engine for 1 year before being promoted and we don't use the rpm mode unless we're drafting, which is very rare for us. Like one of the other guys was saying, your pump and/or firefighters aren't protected in the rpm mode. I trained the crews on the new engines and don't recall anything that says you have to be in rpm mode on tank water and then switch to pressure mode once you get a hydrant. You should just go straight to pressure mode after you put it in pump gear. The problem we're coming across is that the governor seems to be overcompensating when going from tank water to hydrant pressure. I called Class1 and the guy I spoke with was very polite and gave me some things to look in to. Use the link that was provided in another response and try that. Good luck. Be safe.

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